Detoxification and Cleansing Programs

Total Wellness Cleanse

The Total Wellness Cleanse is the newest and most rewarding health-promoting program. This 30-day cleanse is the first of its kind. Nothing like this has ever been done before. It is the only highly-supportive cleansing program that will guide members every single day through a 14-day cleansing process that is geared towards removing dietary stressors, enhancing the body's pH balance, and providing holisitic nutrition guidelines for healing the body's compromised organs and systems. The subsequent 2 weeks (the maintenance phase) is dedicated to working one-on-one with each member to ensure that they transition properly into their customized dietary and lifestyle plans. The result customers will experience greater health, energy, and weight loss improvements than they could ever possibly imagine. The cleanse was created by renowned holistic nutritionists and wellness coaches, Yuri Elkaim and Amy Coates of Total Wellness Consulting. More here...

Total Wellness Cleanse Summary

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Review: Total Wellness Cleanse

Highly Recommended

All of the information that the author discovered has been compiled into a downloadable ebook so that purchasers of Total Wellness Cleanse can begin putting the methods it teaches to use as soon as possible.

When compared to other e-books and paper publications I have read, I consider this to be the bible for this topic. Get this and you will never regret the decision.

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Symptoms That Suggest Detoxification Imbalance

Numerous tests can be conducted to measure liver detoxification functioning. Measurement of metabolite levels before and after challenges with acetaminophen, caffeine, or other chemicals can provide detailed information about an individual's detoxification functions. Testing for phase 1 and phase 2 enzyme polymorphisms are also available and are able to predict susceptibilities to toxic overload. There are, however, a number of readily observable signs that suggest that an individual may have overactive or underactive detoxification functions. Table 9-2 on page 109 summarizes some of the more commonly noted detoxification pathway dysfunctions and their symptoms.

Role Of Pcs In Detoxification Of Heavy Metals Other Than Cadmium

Because plants assimilate various metal ions from soil, the first organ exposed to these ions is the root. Localization of PC synthetase to roots and stems probably provides an effective means of restricting the heavy metals to these organs by chelation in the form of Cd-PC complexes. It has been demonstrated that PCs are able to protect enzymes from heavy metal poisoning in vitro 65,132 many metal-sensitive plant enzymes (rubisco, nitrate reductase, alcohol dehydrogenase, glycerol-3-phosphate dehydrogenase, and urease) were more tolerant to Cd in the form of a Cd-PC complex compared with the free metal ion. Free PCs could reactivate the metal-poisoned enzymes (nitrate reductase poisoned by Cd-acetate) in vitro more effectively than other chelators such as GSH or citrate 65 .

Cell Biology and Biochemistry of ROSProducing and ROSDetoxifying Systems and Their Relation to Water Deficit

ROS-detoxifying mechanisms are a prerequisite of organisms to survive in an oxygen-containing environment as ROS production is inevitably a component of an aerobic metabolism. A large number not only of original papers but also of reviews have been published addressing generation and detoxification of ROS (e.g., Smirnoff 1993 Buchanan and Balmer 2005 Apel and Hirt 2004 Mittler 2002 Mittler et al. 2004 Zimmermann and Zentgraf 2005 Van Breusegem et al. 2008 Dietz 2005 Foyer and Noctor 2005a, b Vieira Dos Santos and Rey 2006), and many of them emphasize the connection between ROS and abiotic stress like drought (Smirnoff 1993 Mittler 2006 Chen et al. 2004 Jaspers and Kangasjarvi 2010 Dat et al. 2000 Cruz de Carvalho 2008 Reddy et al. 2004 Miller et al. 2008). In view of this widespread knowledge, we do not expand on the basics of ROS biochemistry but rather address some special aspects of cell biology related to drought and desiccation. ROS-generating and ROS-scavenging reactions are...

Detoxification Of Electrophilic Xenobiotics

The mechanism of detoxification is conjugation between the xenobiotic at its electrophilic site and the thio-group of glutathione. This conjugation reaction will proceed spontaneously with a large number of electrophilic xenobi-otics of similar softness. The reaction with hard electrophiles requires additional enzymatic support, which is provided by glutathione S-transferase isoenzymes. In any case detoxification totally depends on the availability of glutathione. The homeostasis of glutathione inside the plant is maintained by a complex regulation process (see other chapters of this volume) with synthesis, degradation and long range transport as visible end points. Perturbation of homeostasis and depletion of GSH pools may therefore lead to severe disturbance in a plant's detoxification capacity. Prerequisites for glutathione dependent detoxification

Xenobiotics are detoxified by conjugation

Toxic compounds produced by the plant or which are taken up (xenobi-otics, including herbicides) are detoxified by reaction with glutathione. Catalyzed by glutathione- transferases, the reactive SH group of glutath-ione can form a thioether by reacting with electrophilic carbon double bonds, carbonyl groups, and other reactive groups. Glutathione conjugates (Fig. 12.6) synthesized in this way in the cytosol are transported into the vacuole by a specific glutathione translocator against a concentration gradient. In contrast to the transport processes, where metabolite transport against a gradient proceeds by secondary active transport, the uptake of glutathione conjugates into the vacuole proceeds by an ATP-driven primary active transport (Fig. 1.20). This translocator belongs to the superfamily of the ABC-transporter (ATP binding cassette), which is ubiquitous in plants and animals and is also present in bacteria. Various ABC transporters with different specificities are localized in...

Phase 1 Detoxification

In general, phase 1 detoxification arises from the function of a group of some 50-100 enzymes referred to as cytochrome P450. The healthy functioning of this pathway depends upon an individual's nutritional status, genetics, and level of exposure to chemical toxins. Thus, an individual's risks of developing disease states arising from insufficient detoxification varies greatly. Indeed, this can explain the great variability in patients' susceptibility to, and manifestation of, disease processes such as cancer from environmental pollutants, such as smoking. Clinical evaluation of a patient's risk entails a twofold consideration (1) that of total toxin load and (2) that of his or her ability to process the exposure. Phase 1 detoxification becomes less active with aging. Complicating this decreased function is that blood flow through the liver also diminishes with age. Not surprisingly, there is an increased susceptibility to adverse drug reactions among older adults, whose...

Phase 2 Detoxification

Phase 2 detoxification can be broken down into well-defined detoxification pathways, each with unique abilities for addressing certain toxin categories. Phase 2 detoxification occurs principally via the pathways of acetylation, amino acid conjugation, glucuronidation, glutathione conjugation, methylation, sulfation, and sulfoxidation. Table 9-3. Phase 1 and Phase 2 Detoxification Modulators3

Supporting Detoxification Within The Body

Using this overview and framework of principal mechanisms of liver detoxification, it is wise to focus on essentials for therapeutic intervention, ensuring that the proper balance between phases 1 and 2 detoxification stages is maintained. It is believed that up to 90 of cancer cases arise from the effects of exposure to environmental chemicals, such as those found in air pollution, tobacco, chemically contaminated food, and antimetabolites that deplete nutrients that are essential for proper detoxifyication.16,17 Therefore, choosing nutrients and botanical medicines to support detoxification can improve quality of life, alleviate acute signs and symptoms of excess toxic load, and confer protection over the course of a patient's life. The next sections cover key botanicals, nutrients, and dietary constituents that represent potential clinical interventions for treating acute or chronic cases of toxicity, depending on each patient's condition. This common herb, used frequently in the...

Detoxifying Processes

Detoxification Pathway Dysfunctions the urine (kidneys) and feces (liver and intestines). The skin and lungs provide ancillary support for these processes. Neutralization occurs via a series of complex processes by which toxic chemicals are metabolized to either inert or more readily excreted substances until elimination occurs. When detoxification pathways fail, toxins may accumulate in body tissues, most frequently in fat tissue. This situation emphasizes the importance of nutrient support for antioxidant functioning and detoxification processes for any patient who is experiencing rapid weight loss, when that patient's fat tissues release their toxic loads. The liver is, without question, the leading detoxification organ. On the macroscopic level, the liver filters 2 liters of blood per minute, filtering out large toxins. The liver synthesizes bile and cholesterol that help to bind fat-soluble toxins for excretion. On the microscopic level, this organ neutralizes chemical...

Physicochemical Restriction in Detoxification Process visvis Choice for Getting Rid of Excess Heavy Metal Ions

The redox potential is an important criterion for detoxification by reduction. The redox potential of a given heavy metal should be between the hydrogen-proton couple (0 V) and the oxygen-hydrogen couple (1.229 V) 10 , which is the physiological redox range for most aerobic cells. Thus, Hg2+ (0.851 V) chromate (1.350 V) arsenate (0.560 V) and Cu2+ (0.153 V) may be reduced by the cell, but Zn2+ (-0.762 V) Cd2+ (-0.4030 V) Co2+ (-0.28 V) and Ni2+ (-0.257 V) may not 10 . The second constraint arises in the context of scavenging the reduced product. The reduced product should be able to diffuse out of the cell or it might reoxidize itself. In fact, most reduction products are quite insoluble (Cr3+) or even more toxic (AsO2) than the educts. Logically, even if the cell decides to detoxify a compound like that by reduction, an efflux system should be present to push off the reduced products to the environment. Only in case of mercury do reducibility and a low vapor pressure of the metallic...

Antioxidant Defence for Abiotic Stress Tolerance

Cells, besides a role in scavenging of free radicals and protecting enzymes (Krishnan et al. 2008). The ability to activate protective mechanisms, such as an increase in the activity of scavenging enzymes, is vital for oxidative stress tolerance. Transgenic improvements for abiotic stress tolerances have been achieved through detoxification strategies by overexpressing the enzymes involved in oxidative protection. For example, salt or thermal stress treatment inhibited the growth of wild tobacco and caused increased lipid peroxidation, while overexpression of tobacco glutathione-S-transferase (GST) and glutathione peroxidase (GPX) reduced oxidative damage in the stressed transgenic seedlings (Roxas et al. 2000). Furthermore, overexpression of CuZn superoxide dismutase (SOD) and ascorbate peroxidase (APX) in transgenic sweet potato enhanced tolerance and recovery from drought stress. This was due to a considerable increase in expression of antioxidant enzymes that reduced the levels of...

Secondary Metabolites

Many secondary metabolites are highly toxic to insects. In order to exploit plant tissue containing secondary metabolites insects have evolved behavioral adaptations to avoid the chemicals (Dussourd 1993), or efficient detoxification systems (Brattsten 1992). Presumably, biochemical adaptations are costly (Berenbaum and Zangerl 1992b) and have been considered to be the prime reason for the widespread specificity in plant use among herbivorous insects. For example, 16 out of 72 needle-eating insect species on Scots pine Pinus sylvestris in Sweden feed only on the genus Pinus (Bj rkman and Larsson 1991). However, other phenomena, e.g., escape from natural enemies, also are likely to contribute to the high degree of host plant specialization in herbivorous insects (Bernays and Graham 1988 Stamp 2001).

Nonenzymatic Antioxidants 331 Ascorbic Acid

And nonenzymatic reactions and is thus a powerful radical scavenger. It can directly scavenge 1 O2, O2 and -OH radicals produced in the cell and can protect membranes against oxidative stress. In plant cells, the most important reducing substrate for H2O2 detoxification is ascorbic acid (Turkan et al. 2005). An increase in oxidized ascorbate during Cd stress has been reported by Demirevska-Kepova et al. (2006) in Hordeum vulgare. Yang et al. (2008) also reported that drought stress increases the ascorbate content in Picea asperata. Water stress results in significant increases in antioxidant AsA concentration in turfgrass (Zhang and Schmidt 2000 Vranova et al. 2002 Jaleel et al. 2007). Ascorbic acid shows a reduction under drought stress in maize and wheat, suggesting its vital involvement in oxidative response (Vertovec et al. 2001 Nayyar and Gupta 2006). In contrast to the studies mentioned earlier, in some cases antioxidant activities are enhanced by elevated CO2. In ozone stressed...

Distribution of Heavy Metals and Conjugating Ligands in Root

The increase of the cell walls (CWs) capacity to bind Pb by formation of cell wall thickenings (CWTs) rich in JIM5 pectins, callose and lipids in Funaria hygrometrica plant cells treated with Pb might be regarded as the next step in the development of the plant resistance strategy against this metal based on immobilizing toxic ions within apoplast (Krzeslowska et al. 2009). Binding metal ions within CWs is the important resistance strategy of plant cells in response to Cd (Fig. 1). This has been shown recently for T. caerulescens (Wojcik et al. 2005) Salix viminalis (Vollenweider et al. 2006) and Linum usitatissimum (Douchiche et al. 2007, 2010). In the last named, it was found moreover that exposing plants to Cd resulted in significant increases of both the cell wall thickness and JIM5 pectins formation level in CWs (Douchiche et al. 2007). In S. viminalis, the main Cd sink was pectin-rich collenchyma CWs of the veins. Moreover, also in this case, the amount of pectins slightly...

Distribution of Heavy Metals and Conjugating Ligands in Shoots

(e.g., Pb and As), Cd has a higher propensity to accumulate in shoots other than the roots. Still, there is normally more Cd in roots than in leaves, and even less in fruits and seeds (Wagner 1993). The tendency of tobacco plants to translocate Cd quite efficiently to the leaves contributes to the fact that tobacco smoke is an important Cd source for smokers (Lugon Moulin et al. 2004). But recently, some research showed that tobacco develops an original mechanism of metal detoxification by the exudation of metal Ca-containing particles through leaf trichomes (Choi et al. 2001 Choi and Harada 2005 Sarret et al. 2006).

Heavy Metal Perception in a Microscale Environment A Model System Using High Doses of Pollutants

Abstract The characterization of the mechanisms of heavy metal detoxification has been undertaken through several experimental approaches, where high metal concentrations have been frequently used. A microscale hydroponic system was used to discriminate between the direct and indirect phytotoxic effects that may occur under heavy metal stress at short exposure times. Induction of oxidative stress and generation of stress signaling molecules are some of the physiological responses triggered soon after the exposure of plant cells to heavy metals, which might be part of stress perception mechanisms. The generation of reactive oxygen species, in particular H2O2, ethylene or jasmonate are envisaged as messengers in signaling pathways that may result ultimately in cell senescence and growth inhibition.

Compartmentalized and Interconnected Metabolic Route

The detoxification of 2-PG and its recycling to 3-PGA occurs by the complex photosynthetic carbon oxidation cycle 125, 150 . Because this pathway leads to the consumption of oxygen (oxygenation of RuBP) and production of carbon dioxide (during the recycling of 2-PG) in the light, it is also called photorespiration. The specificity factor of the bifunctional enzyme Rubisco for the carboxylation reaction versus the oxygenation reaction is in the range of 80-100 for most land plants 137 .

Twoelectron reactions

These reactions are important detoxification mechanisms of toxic products produced by plants or xenobiotics. Furthermore, they reflect the ability of conjugated carbonyls to inactivate low-molecular weight and protein thiols in biological systems. The equilibrium constants as well as the rate constants for forward and reverse reaction are extremely dependent on the carbonyl structure, e.g. the mother compound acrolein reacts more rapidly than any other carbonyl to give very stable ad-ducts (half-lives for reverse reaction 4.6 days). 4-Hydroxy-2-alkenals, which derive from polyunsaturated fatty acids, are somewhat less reactive forming also very stable adducts showing half-lives between 3.4 and 19 days. Thus, the biological activity of aldehydic lipid peroxidation products is primarily determined by the reactivity of conjugated carbonyls towards thiol groups and due to the stability of the adducts (Esterbauer et al. 1975). Glutathione -transferases, which...

Enlightening the Mechanisms of Photoinhibition in Chlamydomonas reinhardtii

And NPQ photoprotection are called into question because mutants achieve maximum growth in VHL irrespective of whether the high DES is or is not expressed as NPQ (Forster et al., 2001). Evidently the 5 x slower PS II electron transfer in mutants from herbicide resistant parents was sufficient to attain high DES (requiring some lumen acidification), but inadequate to sustain the ApH necessary for NPQ generation. This perhaps indicates that the role of zeaxanthin as a quencher of reactive oxygen may be more important than its role in excitation dissipation (Niyogi, 1999 Baroli et al., 2003). Confirming earlier interpretations, we found that the mutants survived with high growth rates at VHL in spite of low PS II efficiency (ratio of variable to maximum fluorescence in dark equilibrated samples Fv Fm 0.28 - 0.36) and slow PS II electron transfer, either because of engagement of photoprotection, and or in spite of photoinactivation. The basis of the VHLR phenotype is evidently a...

Generation of O Ho Oh and other ROS in Plant Cells

Other important sources of ROS in plants that have received little attention are detoxification reactions catalyzed by cytochrome P450 in cytoplasm and ER. ROS are also generated in plants at plasma membrane level or extracellularly in apoplast. Plasma membrane NADPH-dependent oxidase (NADPH oxidase) has recently received a lot of attention as a source of ROS for oxidative burst, which is typical of incompatible plant-pathogen interaction. In phagocytes, plasma membrane localized NADPH oxidase was identified as a major contributor to their bacteriocidal capacity (Segal and Abo 1993). In addition to NADPH oxidase, pH-dependent cell wall peroxidases, germin-like oxalate oxidases and amine oxidases have been proposed as a source of H2O2 in apoplast of plant cell. pH-dependent cell wall peroxidases are activated by alkaline pH and in presence of a reductant produces H2O2. Alkalization of apoplast upon elicitor recognition precedes the oxidative burst and the production of H2O2 by...

Dietary Breakdown Products

Toxic breakdown products of protein metabolism include urea and ammonia. The old saying input equals output'' can be mirrored with the saying that output equals input.'' The breakdown processes that fuel the body by breaking down food yield toxic metabolic byproducts. Thus, it is important for patients to maintain a balanced diet and avoid excess that can strain biochemical pathways and provide extra demands on already challenged detoxification processes. Many labs are now providing testing to evaluate functional capacity of detoxification pathways as well as organic acids for cellular energy production.

Negative Regulatory Components

Therefore it was proposed that the LSD1 protein functions as a transcriptional activator (Dietrich et al., 1997). Since LSD1 was recently shown to be part of a signaling pathway leading to the induction of copper zinc superoxide dismutase, it has been suggested that the spreading lesion phenotype of lsdl results from an insufficient detoxification of accumulating superoxide and other ROI, which then trigger a cell death cascade even in unaffected tissue (Kliebenstein et al., 1999).

Basal Constitutive Response

In C. elegans, the DAF-2 DAF-16, the insulin-like signaling pathway regulates dauer formation, longevity, and the responses to environmental stressors and pathogens. It consists of the transmembrane tyrosine kinase insulin-like receptor DAF-2 and its downstream transducer DAF-16. The activation of this signaling cascade leads to the cytoplasmic retention of DAF-16, whereas its downregulation induces translocation of DAF-16 to the nucleus. In such circumstances, nuclear DAF-16 can activate the transcription of two classes of proteins (1) stress resistance proteins, which include those involved in detoxification (e.g. metallothioneins), oxidative stress (superoxidase dismutase, glutathione-S-transferase, catalase) and heat shock responses (2) the antimicrobial immune effectors (lysozymes, LYS-7, LYS-8, saposins, SSP-1, SSP-9, SSP-12, and thaumatins among others) (Lee et al. 2003 Murphy et al. 2003). DAF-16 can act as a transcriptional repressor or activator of gene expression (Shivers...

Effectiveness of Plant Defenses

While the physiological action of some plant chemical defenses is well established, and it is relatively easy to find plant chemicals that repel or poison animals or microbes, it is more difficult to demonstrate that chemical defenses benefit plants in nature, for three reasons. First, there has been repeated evolution of microbes and herbivores that can tolerate or detoxify plant defenses. Many of these plant pests can attack only the few plant species or even tissues to which they are adapted, but no plant

Development Of Transgenic Plants Exploitation Of Hr For Disease Control

Other transgenes inducing lesion-mimic phenotypes encode components of downstream signaling pathways involved in HR development or compounds that activate or interfere with their function. Thus compounds that mimic ion fluxes across the plasma membrane, such as the bacterio-opsin, a bacterial proton pump, or cholera toxin, an inhibitor of GTPase and G-protein signaling, both induce HR-like cell death, which is correlated with PR gene expression and elevated disease resistance (Mittler and Rizhsky, 2000). Likewise, expression of metabolic enzymes that either generate peroxides (e.g., glucose oxidase) or antisense suppression of those that catalyze their detoxification (e.g., catalase, ascorbate peroxidase) was also found to induce

Wholecellbased Biosensors For Detection Of Bioavailable Heavy Metals

These systems can be used as the contaminant-sensing component of the biosensor by detecting the substance for which it is designed to detoxify or excrete. The contaminant-sensing component is combined with the reporter genes to create biosensors that can identify toxic substances at very low levels. When the contaminant-sensing component detects the substance, it triggers the reporter gene. In the development of a mercury-specific biosensor, a hypersensitive clone was constructed using the regulatory sequence along with the mercury (Hg+2) uptake genes merTPC of the mercury resistance operon. Such a clone was found responsive to Hg+2 with as low as 0.5 nM several folds lower than the lowest concentration required to induce the operon without the merTPC.

Conclusion and Future Perspective

Almost all biotic stresses lead to the overproduction of ROS in plants which are highly reactive and toxic and ultimately results in oxidative stress. Oxidative stress is a condition in which ROS or free radicals are generated extra- or intra-cellularly, which can exert their toxic effects to the cells. These species may affect cell membrane properties and cause oxidative damage to nucleic acids, lipids, and proteins that may make them non-functional. However, the cells possess well-equipped antioxidant defence mechanisms to detoxify the detrimental effects of ROS. The anti-oxidant defences could be either non-enzymatic (e.g. glutathione, proline, a-tocopherols, carote-noids, and flavonoids) or enzymatic (e.g. SOD, catalase GPX, and GR). It is well known that plant cells and its organelles like chloroplast, mitochondria, and peroxisomes employ antioxi-dant defence systems to protect themselves against ROS-induced oxidative stress.

Cd Uptake from Soil to Roots

Most studies have shown that the main site of Cd accumulation in roots is the apoplast, particularly cell walls. Using energy-dispersive X-ray microanalysis, Cd was determined in cortex parenchyma cells, endodermis, parenchyma cells of the central cylinder, and xylem vessels in T. caerulescens (Wojcik et al. 2005). After treatment with 20 ppm Cd, about 13 of the total Cd in T. caerulescens roots was associated with organic acids (Boominathan and Doran 2003). Nedelkoska and Doran (2000) have found retention of almost the whole pool of Cd taken up in the fraction of cell wall of Thlaspi roots, and then diffused into the symplast after 7-10 days of exposure to 200 p.M Cd. The authors also suggested that such a delay in Cd transport through membranes inside cells is an important defense mechanism against Cd toxicity, enabling simultaneous activation of intracellular detoxification mechanisms of Cd such as chelation and antioxidative defense.

Mechanisms In Amf To Tolerate Ptes

Levitt 57 proposed three basic strategies for organisms dealing with high PTE concentrations avoidance, detoxification, and biochemical tolerance. The avoidance mechanism involves PTE exclusion mechanisms, which operate at two levels restriction of uptake and restriction of transport. The process of detoxification is essentially similar, but avoidance of toxicity results from subcellular PTE concentration or by binding. Biochemical tolerance reflects the presence of specialized metabolic pathways and enzymatic adaptations.

Reactions on green pigments 2321 Chlorophyllase

A typical N-terminal transit peptide is missing in some of the cloned CLHs, such as Arabidopsis CLH1 or CaCLH1 from Chenopodium album. Instead, Ca-CLH1 seems to be glycosylated and has motifs suggesting localization in the vacuole (Tsuchiya et al., 1999). This absence was explained by a possible second pathway localized inside the vacuole, where CLH together with unknown oxidases would ca-tabolize chl (Takamiya et al., 2000). The finding of a mass exodus of chl-containing globules from senescent chloroplasts (Guiamet et al., 1999) supported this idea. But so far neither the oxidases nor catabolites of such a pathway have been found. Experiments on subcellular localization and the analysis of mutants will be required to elucidate the in vivo role of CLHs. Notably, downregulation of AtCLH1 did not cause an obvious senescence-related phenotype (Benedetti and Arruda, 2002 Kariola et al., 2005), and a role of AtCLH1 in regulating defense pathways in plants through the detoxification of...

Cell Wall Binding and Vacuole Sequestration

Plants have a range of potential mechanisms at the cellular level that might be involved in the detoxification and thus tolerance to heavy metal stress (Hall 2002). Cell wall binding and vacuolar sequestration are the two essential detoxification mechanisms that play a vital role in hyperaccumulation of heavy metals (Cosio et al. 2004). hydroponically, Zn and Cd were accumulated in the cell wall of the rhizosphere as Zn Cd phosphates (Kupper et al. 2000). Cell wall binding can prevent Cd from being transported across the plasma membrane. This delay in transmembrane uptake may represent an important factor in the defense against Cd poisoning in T. caerulescens, allowing time for activation of intracellular mechanisms for heavy metal detoxification (Nedelkoska and Doran 2000). The vacuole, in turn, is generally considered to be the main storage site for metals in yeast and plant cells (Salt and Rauser 1995). Compartmentalization of metals in the vacuole is also part of the tolerance...

Evolution of Cd Hyperaccumulation

Apart from the numerous studies on physiological and molecular mechanisms involved in Cd hyperaccumulation and detoxification, as discussed above, perhaps the most fundamental question is why these unusual species accumulate Cd to concentrations that are toxic to most other organisms. Since 1990s, the ecological and evolutionary significances of metal hyperaccumulation have attracted considerable attention. Five principal hypotheses have been postulated, including drought resistance, metal tolerance disposal, elemental allelopathy, inadvertent uptake, and defense against herbivores or pathogens (Boyd and Martens 1998). There is little evidence linking hyperaccumulation with drought resistance, metal tolerance disposal, and elemental allelopathy (Boyd 2004 Mcnair 2003). According to the inadvertent uptake hypothesis, Cd accumulation is possibly mediated by channels

Antioxidant Systems Under Cd Stress

(Leon et al. 2002) and sunflower (Laspina et al. 2005), while the opposite effect was observed in radish roots (Vitoria et al. 2001). Especially interesting is that light may interfere with the Cd-dependent catalase activity, as it has been shown that Cd2+ treatment of leaf discs under light decreased CAT activity and increased carbonyl groups content, which suggested that CAT inactivation could be due in part, to the oxidation of the protein under this condition (Azpilicueta et al. 2007), although in pea plants treated with Cd, no changes in the pattern of CAT oxidation were observed (Romero-Puertas et al. 2002). In addition to CAT, the enzymes of the ascorbate-glutathione cycle also remove H2O2, especially in cellular compartments where H2O2 exits and there is no catalase (Gutteridge and Halliwell 2000). This cycle is composed of four enzymes ascorbate peroxidase (APX), monodehy-droascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glu-tathione reductase (GR) which...

Overexpression Of Mts As A Means To Increase Cadmium Tolerance

An important pathway by which plants detoxify heavy metals is through sequestration with heavy metal-binding peptides called phytochelatins or their precursor, glutathione. To identify limiting factors for heavy metal accumulation and tolerance and to develop transgenic plants with an increased capacity to accumulate and or tolerate heavy metals, the Escherichia coli gshII gene encoding glutathione synthetase (GS) was overexpressed in the cytosol of Indian mustard (Brassica juncea). The transgenic GS plants accumulated significantly more Cd than the wild type shoot Cd concentrations were up to 25 higher and total Cd accumulation per shoot was up to threefold higher. Moreover, the GS plants showed enhanced tolerance to Cd at the seedling and mature plant stages. Cd accumulation and tolerance were correlated with the gshII expression level. Cd-treated GS plants had higher concentrations of glutathione, phytochelatin, thiol, S, and Ca than wild-type plants. The conclusion was that, in...

NO Function and Protection Under Cd Stress

Recently, a study in which CATMA arrays were used, has shown the effects of NO in roots of Cd2+ treated plants (Besson-Bard et al. 2009). Forty-three genes related to iron homeostasis, proteolysis, nitrogen assimilation metabolism and root growth, were identified to as being regulated by nitric oxide. NO can also regulate cellular responses through posttranscriptional modifications such as S-nitrosylation of proteins (Lindermayr et al. 2006 Romero-Puertas et al. 2008). A decrease in S-nitrosylation of CAT protein under Cd stress was observed (Romero-Puertas et al. submitted). CAT, a key enzyme involved in H2O2 detoxification in peroxisomes is S-nitrosylated during physiological conditions (Romero-Puertas et al. submitted) and the reduction in S-nitrosylation could be related to the slight increase in CAT activity previously observed in isolated pea leaf peroxisomes (Romero-Puertas et al. 1999). Additionally, it has been shown that in plants treated with Cd there is an increase in the...

Regulatory Aspects Of The Glutathione System Under Stress Impact

The control of glutathione pool and the glutathione redox state itself seems to be even more complicated (Figure 5). Glutathione synthesis is apparently under redox control, possibly by GSH GSSG ratio itself. In Arabi-dopsis, the translation of protein for y-GC synthetase, the rate limiting enzyme for GSH synthesis, is repressed by high GSH GSSG ratios. (Xiang and Betrand 2000). Furthermore, sulphur assimilation into cysteine as a requirement for GSH synthesis can also be oxidatively induced. For example, the expression rates and the activities of the key enzymes APS-reductase and ATP-sulphurylase (but not cysteine-synthetase) increased upon a decreased GSH GSSG-ratio in maize roots. This is even more remarkable because most enzymes of assimilation pathways in the chloroplasts are induced under the reducing conditions of a highly active light-driven electron transport (Fluck-inger et al. 2000). ATP-sulphurylase activity increased in canola roots upon mild oxidative stress, which also...

Organelles Involvement in Cd Stress

ROS production after cadmium stress differs in the nature of the source and localization in the cell. It seems that NADPH oxidase from plasma membrane is one of the first enzymes involved in ROS production in response to heavy metal (Olmos et al. 2003 Garnier et al. 2006). Other organelles, however, such as mitochondria (Garnier et al. 2006), peroxisomes (Romero-Puertas et al. 1999) and chloroplasts (Bi et al. 2009), are also involved and play a key role in ROS release and or detoxification in response to Cd. Several studies have shown that the vacuole is a site of accumulation of different heavy metals (Cobbett 2000 Verbruggen et al. 2009). Actually, chelating complexes formed by Cd can be transported into the vacuoles, preventing the free circulation of Cd ions and placing them into a limited area (Sanita di Toppi and Gabrielle 1999). On the other hand, it has been reported that Cd2+ increase H2O2 and O2 - accumulation in mitochondria (Heyno et al. 2008 Garnier et al. 2006)....

Physiological pathways involving Cblcipk signaling modules

An increase in Ca2+ levels in the cytoplasm (Pauly et al, 2000), salt tolerance could therefore involve Ca2+ signaling and the signal could be transmitted via CBL-CIPK pathways for salt detoxification (Hasegawa et al., 2000). In this context, studies have established that SOS3 CBL4-SOS2 CIPK24 may directly regulate the downstream component SOS1, a putative Na+ H+ antiporter (Shi et al., 2000), thereby enhancing the salt detoxification process. More recent studies (Kim et al., 2007 Quan et al., 2007) placed another CBL, CBL10, in the salt tolerance pathway. Interestingly, CBL10, like SOS3 CBL4, also interacts with and appears to function through SOS2 CIPK24. However, unlike SOS3 CBL4 that functions mainly in the roots, CBL10 is expressed and functions almost exclusively in the shoots leaves (Kim et al, 2007 Quan et al, 2007). Perhaps the most unique feature of the cbl10 mutant is that the mutant plants, despite being more sensitive to salt, accumulate less salt than the wild type (Kim...

Proteomics of Plant Hyperaccumulators

Abstract Plant metal hyperaccumulators take up and detoxify high concentrations of metal ions in their roots and shoots. They constitute an exceptional biological material for understanding mechanisms regulating plant metal homeostasis and plant adaptation to extreme environments. Hyperaccumulation physiology has recently also been studied with molecular tools. Indeed making use of transcriptome analysis it has been demonstrated that different expression patterns of genes accompanied different responses to metals between hyperaccumulator and non-hyperaccumulator plant species. The proteomic approach can also be powerful in dissecting the hyperaccumulator phenotype and the complex involvement of the protein regulation in this phenomenon. This chapter focuses on the recent developments in the application of proteomics to the analysis of hyperaccumulators providing a comprehensive review of key literature data of plant metal in particular Cd, Ni and Zn hyperaccumulation.

Oxidative Stress and Cell Defenses

Ascorbate peroxidase is found in higher-order plants, chlorophytes, and red algae. This enzyme has a high specificity for ascorbate (or ascorbic acid) as the reducing substrate, and it subsequently catalyzes the reduction of hydrogen peroxide into water (Carvezan 2008). The ascorbic acid acts both as a cofactor and reducing agent for the enzyme, allowing the enzyme to detoxify various organic radicals, counteract O2' and H2O2 and remove active oxygen (Halliwell and Gutteridge 1989).

Some plants emit prussic acid when wounded by animals

If the cell is wounded by feeding animals, the compartmentation is disrupted and the glycosidase comes into contact with the cyanogenic glycoside. After the hydrolysis of the glucose residue, the remaining cyanhydrin is very unstable and decomposes spontaneously to prussic acid and an aldehyde. A hydroxynitrile lyase enzyme accelerates this reaction. The aldehydes synthesized from cyanogenic glycosides are often very toxic. For a feeding animal, the detoxification of these aldehydes can be even more difficult than that of prussic acid. Due to the formation of the two different toxic compounds, cyanogenic glycosides are a very effective defense system.

Stress Response Circuits in Context

Generally, drought can be integrated into a global stress recognition and integration response network that can provide a view of underlying complexities (Fig. 13.1). Sensing of a particular stress condition includes specific reactions that identify the stress, but owing to the sensing of injury that accompanies any stress, different responses are elicited by additional signalling pathway or pathways that measure injury. While the abiotic stress-specific pathways lead to responses that are to some degree known, signal integration begins to affect cell division expansion, growth, and development. Initiated by injury, for example, the components of endoplas-matic reticulum and denatured protein signals, detoxification signals begin to control damage and affect repair reactions. Depending on the severity of a stress, repair and stress-specific countermeasures can lead to tolerance, but may also lead to (programmed) cell and plant death (Fig. 13.1). Many components linking tolerance to...

Natural Functions Of

Natural functions for the GST have been discussed since their discovery. The ubiquitous distribution and the abundant presence of GST in various tissues of animals and plants may be a sign for their obvious importance. GST of mammals, especially rodents and human have been investigated thoroughly for their physico-chemical and catalytic properties (Mannervik und Danielson 1988, Picket and Lu 1989, Daniel 1993) because of their important role in toxin conjugation, drug metabolism and anticancer therapy. Natural functions of GST in plants have only scarcely been investigated (Table 5). However, there are several reports on the detoxification of toxic endogenous metabolites. For example, in wheat all eight characterized iso-forms have activity with crotonaldehyde and an isothiocyanate. Furthermore, they exhibit all glutathione peroxidase activity as do certain maize GSTs. Phytohormones, fungal and bacterial toxins may also be conjugated, but experimental evidence is scarce....

Other Members Of The Mate Family

Functionally characterized members of the MATE family appear to efflux low molecular weight organic compounds from the cell cytoplasm either out of the cell or into a subcellular compartment (for a summary, see Rogers and Guerinot, 2002). There are at least 56 MATE family members in Arabidopsis (Li et al., 2002 Rogers and Guerinot, 2002). They play roles in processes as diverse as salicylic acid localization, flavonoid transport, and detoxification. Therefore it is very difficult to predict a function for a newly discovered MATE protein simply based on protein sequence similarity to a previously characterized MATE family member.

Involvement of Plant Antioxidant Systems in ROS Signaling

The balance between ROS production and ROS scavenging is a critical aspect for redox homeostasis. This balance can be altered by abiotic and biotic stress conditions. During normal cell metabolism ROS content has to be maintained at a low steady-state level however, as it has been already mentioned, new ROS are continuously produced in aerobic organisms. The continuous presence of ROS, whose concentration depends on the environmental conditions or on cell tissue developmental phase, might have moved the evolution to use ROS as molecular signals in several processes. In particular, plant growth and development as well as hormonal signaling and the activation of defense mechanisms also depend on the alteration in ROS levels. It has been observed that treatments with CAT of soybean cells inoculated with avirulent pathogens block the induction of plant defense genes, such as those encoding for glutathione peroxidase and glutathione transferase (Levine et al. 1994). The latter enzyme is...

Compartimentation Of Glutathione Conjugates

On the background of these metabolism data, it is logical that glutathione conjugates may be intermediates rather than end products of detoxification. This topic has been reviewed extensively elsewhere (Schr der 1997). Elaborate investigations of herbicide metabolism in several plant cell cultures have elucidated that GS-conjugates have only short lifetimes in the cultured cells, and that they are rapidly further metabolized. First evidence for the enzymatic background of these cleaving reactions has been obtained only recently. Wolf et al. (1996) identified a specific carboxypeptidase for the cleavage of xenobiotic glutathione conjugates in the vacuoles of barley. Car-boxypeptidases are exopeptidases cleaving terminal amino acids from poly-peptides, whereas the physiological role of endopeptidases would be the regulation of enzyme activities via the cleavage of internal peptide bonds in polypeptides (Zuber and Matile 1968). A natural function for exopeptidases has been found in the...

Biotechnological Potential of ECM Fungi Producing Metal Chelating Agents

The revegetation of metal-contaminated soils is another important application of plants mycorrhized with ECM fungi producing a wide range of chelators siderophores, LMW organic acids, MTs, PC, and GSH. Given that these chelators contribute to the detoxification of metals through intracellular or extracellular mechanisms, the fungal species that produce them must protect their host plants in contaminated environments. This protection consists of excluding metals or accumulating them in their fruiting bodies, using both ways to prevent their entry into the mycorrhized roots. The use of plants in the bioremediation of soils contaminated by metals, aided by synthetic chelators like EDTA and called assisted

Mechanisms of herbicide resistance 1221 Target site resistance

There have been only limited reports of resistance to this class of herbicide and little is known regarding the resistance mechanisms responsible. No evidence of target-site resistance involvement has yet been found and it is thought that most cases of resistance are a result of enhanced herbicide metabolism or sequestration away from the site of action. In Lolium perenne and Conyza bonariensis increased levels and activities of enzymes that detoxify active oxygen species have been measured in resistant biotypes. These are superoxide dismutase, ascorbate reductase and glutathione reductase (Shaaltiel and Gressel, 1986). Other studies with C. bonariensis have suggested the immobilisation of paraquat in resistant biotypes, possibly by binding to cell wall components, so that less of the herbicide can reach the thylakoid. Alternatively, paraquat uptake and movement may be reduced in resistant biotypes of Hordeum glaucum.

Overall Naturopathic Approach

There is some evidence that, for many patients, a week of fasting followed by a vegetarian diet will reduce the symptoms of RA over the course of a year.38 During the fasting period of the study cited, subjects were allowed to eat garlic, vegetable broth, a decoction of potatoes and parsley, herbal teas, and the juices of carrots, beets, and celery. (Note that, in addition to potentially suppressing the immune system because of hypocaloric intake, this fasting diet also provides an excellent source of phytochemicals that assist in detoxification and is itself rich in antioxidants.) Following the fasting, subjects introduced new foods one at a time, discontinuing them if any increase in pain, stiffness, orjoint swelling was noticed. If, after a week of waiting, reintroduction resulted in a repeat exacerbation, then that item was removed for the rest of the study period. New food items being introduced excluded gluten, meat, fish, eggs, dairy foods, refined sugar, citrus, salt, strong...

Application to bioindication

Two main classes of biomonitoring techniques, direct and indirect, can be distinguished. Direct biomonitoring techniques use organisms as in situ biological assays of pollution levels. This is how bryophytes are most often used in biomonitoring, with pollutant concentrations being directly measured in moss tissues. Sometimes, indicators of plant stress, such as pigment ratios (Lopez et al. 1997) or the concentration of enzymes involved in the detoxification process of pollutants (Roy et al. 1995, Schrenk et al. 1998), are also used. Indirect biomonitoring, by contrast, involves detecting how variation in community attributes, such as species composition, abundance and diversity, may be explained by changes in the environment.

Coffee And Gastrointestinal And Liver Health

Because of the unique relationship between caffeine and the hepatic microsomes that metabolize it, it has been proposed that fasting plasma caffeine concentration may serve as a guide to measuring the physiologic impairment arising from chronic liver disease.59 Caffeine can provide, via hepatic detoxification testing, information on whether an imbalance between phase 1 and phase 2 detoxification pathways are present. The unique physiologic impact of caffeine in the liver has also led to research on the relationship between serum gamma glu-tamyltransferase a measure of liver damage and smoking that suggests coffee may help mitigate some of the damage associated with smoking demonstrated by decreased induction of gamma glutamyltransferase in smokers.60 What also supports this trend is an observation of an increase in gamma glutamyltransferase in women from Norway who decreased their consumption of boiled coffee.

Interest in Phytoremediation

AtHMA4 and its orthologs are interesting since they allow a higher translocation of Zn2+ and Cd2+ and presumably Pb2+ and Co2+ from the roots to the shoot (Verret et al. 2004), allowing a detoxification of the roots and thus a better tolerance of the plant and a higher yield of phytoextraction. While the increase in Zn2+ and Cd2+ transfer in 35S AtHMA4 transgenic plants was less than a doubling, the first experiments on actual polluted soils have shown that the transgenic lines were able to extract 3.1-fold more Cd2+ and 2.8-fold more Zn2+ than the wild-type plants (C. Sarrobert, Institut de Biologie Environnementale et Biotechnologies, France, personal communication). Thus, a major interest of HMA4 is to give a selective advantage in case of a multi metallic pollution and this may be the reason why this gene has been under a high selection pressure in hyperaccumulators which have to face such types of environment. Genes encoding AtHMA4 orthologs have been found highly expressed in...

Subcellular Proteome in Defense and Stress Responses

Chloroplasts and Mitochondria Subcellular fractionation and purification of organelles have provided attractive advantages to low-abundance protein separation in proteomic analysis. The proteomes of some organelles such as chloroplast, mitochondria, nuclei, and other subcellular compartments were studied in plants. Of the organelles, the chloroplast and the mitochondria proteomes are by far the most comprehensively studied. However, these organelles were not investigated in the plant defense proteome. The resistance response against pathogen attack usually triggers a rapid HR that is tightly associated with rapid changes in calcium influx, generation of ROS, expression of PR proteins, production of phytoalexins, and cross-linking of components of the cell wall. Both chloroplasts and mitochondria are additional potential sources of ROS and possess well-developed mechanisms to rapidly detoxify free radicals. Therefore, changes to the proteome of chloroplasts and mitochondria are of...

And Chemical CaMg Ratio LMWOAs Factors Influencing Phytoremediation Efficiency

In the broad spectrum of organic compounds present in the rhizosphere, particular attention is focused now on LMWOAs. Organic acids such as malic, oxalic, acetic or citric are recognized as the most significant ones in many different processes in the rhizosphere. Depending on their degree of dissociation (efficiency), and the amount of carboxylic groups in the molecule, acids can appear in the form of differently charged anions, which in consequence results in the possibility of metal cations' complexation and relocation from the soil. This is the reason that acids are reported as components of the soil environment which in the rhizosphere take part in many processes, e.g. in dissolving and uptake of nutrients (e.g. P and Fe) by plants and microorganisms, decrease of stress associated with anaerobic conditions, dissolving soil minerals leading to pedogenesis, and detoxification of heavy metals by plants (e.g. Al).

Common Changes in the Proteome in Response to Different Abiotic Stresses

Although we have summarized the recent proteome studies on stress responses for single stress factors, it is evident that under many natural conditions the plants have to respond to a combination of stresses. Consistent with biochemical and molecular data, proteome approaches also indicate an overlap in the cellular responses to different stresses, such as detoxification of ROS by enzyme components as a ubiquitous element of defense. It should also be mentioned that due to limitations in current techniques, proteome analysis is likely to be restricted to the more abundant proteins of central metabolic pathways, implying that specific aspects of cellular responses characteristic to certain stress factors might not yet be detected with current methodology. However, a survey of published data indicates that in many experimental systems, fundamental reprogramming of central metabolic routes can be monitored. Whereas changes in the abundance of proteins representing house-keeping functions...

A 20052006 Update Of The Contribution Of Proteomics To Rnf Symbiosis

Transformation of a free-living bacterium to a nitrogen-fixing bacteroid results in significant physiological and developmental changes in rhizobia. To understand the cellular events occurring in bacteroids isolated from nitrogen-fixing root nodules, a 2D gel proteome map was constructed using the total protein extracts from B. japonicum bacteroids 59 . Among the 400 protein spots that could be detected, 180 were identified using MALDI-TOF-MS by searching the available database for B. japonicum. The data showed that the bacteroid expressed a dominant and elaborate network for nitrogen and carbon metabolism, which is closely dependent on the plant-supplied metabolites. Although the B. japonicum genome encodes over 700 genes related to transport, only a number of specific ABC transporters appeared to be expressed in bac-teroids. They also seemed to lack a defined fatty acid and nucleic acid metabolism. Proteins related to protein synthesis, scaffolding, and degradation were among the...

Defence Related Signalling Compounds

No significant oxidative burst was detectable at the time of giant cell induction and at later time points (Melillo et al. 2006 Das et al. 2008). ROS are also produced in host plants during interaction with rhizobia notably in the infection process (Santos et al. 2001). So the bacteria have to protect themselves from these defence molecules and bacterial strains with impaired capacity to detoxify H2O2 have deficiencies in their symbiotic capacities. Despite negative effects, ROS has been reported as signalling molecules in the control of nodulation process, and a threshold level of ROS would be required for a harmonious nodule development (Pauly et al. 2006). Additional major molecules involved in the regulation of the cellular redox state, nitrogen monoxide (NO) and glutathione (GSH) are detected in response to rhizobia and required in proper nodule development (Frendo et al. 2005 del Giudice et al. 2011). Unfortunately, the role of GSH and NO in giant cell...

Interpretation Of Transport Data

It should be noted that our efforts to describe the export and emission of scent molecules in quantitative terms might be complicated by (at least) one other factor. The absence of both appreciable internal pools of scent volatiles and the biosynthetic enzymes of such compounds in scent-emitting floral tissue of Jasminum species prompted Watanabe et al.68 to discover that fragrance components are stored as nonvolatile glycosides. However, Loughrin et al.69 found that the level of glycosid-ically bound volatiles in Nicotiana species was not correlated with the emission levels of such volatiles, but with the age of the flower older, senescing flowers had higher levels of stored glycosides. It has been speculated that glycosides are either precursors, storage forms, or detoxification products of scent compounds. The role of these derivatives, as well as their amounts, may depend on plant species and physiology. Hence the (reversible ) formation of glycosides must be regarded side branch...

Ascorbate A Key Player in Leaf Development and Responses to the Environment

The production of superoxide and H2O2 as a result of processes associated with photosynthesis has been described many times previously (Asada, 1999 Foyer and Noctor, 2000, 2003) and will not therefore be discussed here in detail. Chloroplasts contain a hierarchy ofH2O2-detoxificationmechanisms in which ascorbate plays a central role (Noctor and Foyer, 1998 Foyer and Harbinson, 1999 Foyer and Noctor, 2000). Ascorbate also functions in the systems that reduce the probability of ROS generation in the chloroplast, particularly the xanthophyll cycle, in which ascorbate provides the reducing power necessary to convert violaxanthin to zeaxanthin in the de-epoxidation sequence (Demmig-Adams and Adams, 1992 Foyer and Harbinson, 1999). Thus, like the regeneration of tocopherol discussed above, the violaxanthin de-epoxidation reaction oxidizes ascorbic acid in the lumen. Hence, two intrinsic defense processes protecting PS II draw on the lumen ascorbate pool. Since no kinetic evidence has been...

The transcriptional regulation of cold and droughtinducible genes

Transcripts of many genes with different functions are induced by various environmental stresses. The inducible genes can be divided into several groups according to their functions. One group includes genes for signal transduc-tion pathways as we have discussed above. The other genes encode effector proteins such as LEA proteins, enzymes for osmolyte biosynthesis, and detoxification enzymes. Transcription factors regulate the expression of stress-inducible genes through direct binding to conserved cis-elements in the promoter regions of the inducible genes. These cis-elements include the ABA responsive element (ABRE), the dehydration responsive element (DRE) C-repeat (CRT), MYCRS (MYC recognition sequence) MYBRS (MYB recognition sequence), and other sequences. Earlier studies using yeast one-hybrid assays identified several important transcription factors that bind to stress responsive cis-elements (Stockinger et al., 1997 Liu et al., 1998 Choi et al.,

Effects of phenolic acids upon germination of Calluna seed

Since seed of Calluna normally falls directly onto soil enriched in phenolic compounds, phytotoxicity can be experienced from the germination phase onwards. Incorporation of these compounds into agar on which Calluna seed was sown, showed that some can indeed inhibit the germination process (Fig. 4). Salicylic and -methoxybenzoic acids were the most toxic individual acids but, more importantly, the field mixture also produced a 17 inhibition. In the presence of the fungus, however, such an inhibition was almost entirely removed. Thus even before infection takes place, the presence of endophyte mycelium in the environment around the root can lead to detoxification.

Pathogens With Evolved Mechanisms To Counteract Plant Defense Responses

As described previously, plant pathogens evade -gene-mediated resistance by modification of the elicitor proteins either by mutations in, or deletion of, the Avr genes or by (down-)regulation of Avr gene expression. Yet, when the circumvention of elicitor detection fails, or when the elicitor component is essential for virulence, pathogens require mechanisms to subvert the induced plant defense responses. Indeed, plant pathogens counteract plant defenses by secreting enzymes that detoxify defense compounds, including phytoalexins, or use ATP-binding cassette (ABC)-transporters to mediate the efflux of toxic compounds (as reviewed by Idnurm and Howlett, 2001). Moreover, some bacterial pathogens interfere with R-gene-mediated resistance by secreting proteins that mask the presence of a particular AVR effector protein (Ritter and Dangl, 1996).

On Plants Stress Responses

Zinc is the most important micronutrient that is involved both directly and indirectly in the metabolism of ROS as well as protection of structural components of cell against ROS. In leaves of different wheat and rice cultivars, deficient supply of Zn decreased total SOD activity and, more distinctly, CuZn-SOD activity, whereas Mn-SOD activity was not affected by Zn deficiency (Cakmak et al. 1997 Hajiboland 2000). Interestingly, change in the activity of CuZn-SOD could be used for interpreting different susceptibility of various wheat (Yu et al. 1999b) and rice (Hajiboland 2000) genotypes to Zn deficiency (Table 16.2). Zinc may indirectly be required for high activity of the enzymes involved in H2 O2 detoxification. Reports on the effect of Zn deficiency on the activity of CAT, APX and glutathione reductase (GR) are contradictory. Some reports demonstrated increase (Tewari et al. 2008 Hajiboland and Beiramzadeh 2008) and others reduction of their activity under Zn starvation (Yu et...

Variations in Heavy Metal Tolerance in Plants

Tolerance is based on two different strategies (1) to avoid the entry of excess HM into the plants and (2) to achieve effective intracellular detoxification. The main tolerance-related mechanisms are already wellknown, the most important of which include (1) the reduced uptake and or accelerated excretion of HM by the cells, (2) the metal detoxification and compartmentalization, (3) the control of the metal induced oxidative stress, etc. (Vassilev and Nikolova 2010). The scientific interest with respect to the plant tolerance toward HM has become considerably larger in recent years. On the one hand, this is due to possible usage of tolerant plants for phytoreme-diation of soils contaminated by HM (Kulakov et al. 2009), and on the other hand, the interest is a result of the possible wider usage of the plants as model objects for ecotoxicological studies (Hock and Elstner 2005). The number of research papers related to the identification of plants that have high tolerance and...

Equilibrium Models Concentration Ranges and Biological Functions of Metal Ions

Thus, there is negative feedback in the environment metallome system, exactly tantamount to detoxification. For so-called semi-metals some of which also form colloquial complexes, like Sb, Bi, Te, the speciation pathway of biomethylation (Thayer 1995) will remove their electrophilic properties altogether, turning the cations into ligands (donors) of their own, whereas with other elements (Ge, Sn, Pb, Pt, Au, Cd or Hg) acceptor properties are substantially altered (see the data (c and x values, Table 2.3) for R2Sn2+, R3Sn+ and R3Pb+ species) but do not vanish. Of course, redox processes also influence acceptor properties (cp. the data for different oxidation states of V, Fe, Ce or Tl).

Kna1 Saltol Nax Torelant Salinity

Two-dimensional gel electrophoresis using a series of hydroponics-based salinity stress experiments in contrasting genetic mapping parents of barley cvs Steptoe and Morex. The proteome analysis of roots from both genotypes revealed cultivar-specific and salt stress-responsive protein expression. Twenty-six proteins could be identified by mass spectrometry. Among those, two proteins involved in the glutathione-based detoxification of reactive oxygen species (ROS) were more abundant in the tolerant genotype. Most common genes used for genetic engineering of stress-tolerant plants include transcription factors, signal transduction genes, water channel proteins, ion transporters, detoxifying genes, molecular chaperones, dehydrins, and osmopro-tectants (Table 4.4).

For Engineering Tolerance

As previously stated, abiotic stress generates an increase in reactive oxygen species that may be deleterious to normal cellular functions. Therefore, several oxidative-stress-related genes have been employed in developing transgenic plants tolerant to various stresses (Hussain et al. 2008). For example, transgenic tobacco plants overexpressing chloroplastic Cu Zn-SOD showed increased resistance to oxidative stress caused by salt exposure (Tanaka et al. 1999 Bartel 2001). Transgenic alfalfa (Medicago sativa) plants expressing Mn-SOD had reduced injury from water-deficit stress, as determined by chlorophyll fluorescence, electrolyte leakage and regrowth (McKersie et al. 1996). Simultaneous expression of genes encoding three antioxidant enzymes copper zinc superoxide dismutase, ascorbate per-oxidase and dehydroascorbate reductase in the chloroplasts of tobacco plants conferred enhanced tolerance to oxidative stresses caused by paraquat and salt (Lee et al. 2007). Similarly,...

Thioldisulphide interchange reactions

In plant cells GSH fulfils several functions. As an antioxidant GSH protects cell constituents against oxidative stress, e.g. GSH - in cooperation with ascorbate - removes reactive oxygen species which are formed as byproducts of the photosynthesis. Furthermore, GSH accomplishes protective functions by conjugation of xenobiotics and as starting material for the synthesis of phytochelatins for the detoxification of heavy metals. Additionally, GSH serves as storage compound for organic sulphur. Through enzymatic degradation cysteine can be recovered if needed. Novel functions of GSH are emerging (Sies 1999). One is the hopping of nitric oxide between thiol groups in a process known as trans-nitrosation (Al-Mustafa et al. 2001). A major focus of current research is directed to the role of thiols in signalling, i.e. the control and modulation of pathways leading to gene expression (Sies 2001). Talalay P., Prochaska H. J., Spencer S. R. 1990. Regulation of enzymes that detoxify the...

Review Of Heat And Light Stress In Medicinal Plants

Arfan M, Athar HR, Ashraf M (2007) Does exogenous application of salicylic acid through the rooting medium modulate growth and photosynthetic capacity in differently adapted spring wheat cultivated under salt stress J Plant Physiol 6 685-694 Asai T, Tena G, Plotnikova J, Willmann MR, Chiu WL, Gomez-Gomez L, Boller T, Ausubel FM, Sheen J (2002) MAP kinase signaling cascade in Arabidopsis innate immunity. Nature 415 977-983 Asselbergh B, Vleesschauwer D, Hofte M (2008) Global switches and fine-tuning - ABA modulates plant pathogen defense. Mol Plant Microb Int 21 709-719 Athar HR, Khan A, Ashraf A (2008) Exogenously applied ascorbic acid alleviates salt-induced oxidative stress in wheat. Environ Exp Bot 63 224-231 Azevedo H, Lino-Neto T, Tavares RM (2004) Salicylic acid up-regulates the expression of chloroplastic Cu, Zn-superoxide dismutase in needles of maritime pine (Pinus pinasterAit.). Ann For Sci 61 847-850 Bandurska H, Stroinski A (2005) The effect of salicylic acid on barley...

Silica Needles and Raphids Made of Calcium Oxalate

Lev-Yadun and Halpern (2008) proposed that many plant species without thorns, spines, or prickles possess an alternative one of two types of usually internal (but sometimes external), sharp, microscopic defensive structures silica needles and raphids (which are needles made of calcium oxalate). Silica bodies in plants are formed by the ordered biological deposition of silicon that enters the plant via the roots (Richmond and Sussman 2003) , Silica bodies have several known functions structural, serving as cofactors in the detoxification of heavy metals, and defense from herbivory (e.g., Richmond and Sussman 2003 Wang et al. 2004) , Lev-Yadun and Halpern (2008) discussed their specific potential defensive function enabling the penetration of microorganisms into the bodies of herbivores. Thousands of plant species belonging to many families produce raphids (Franceschi and Horner 1980) , Usually, raphids are formed in specific parenchymal cells that differ from their neighboring cells...

Mechanisms of Metal Tolerance in ECMF

Cytoplasmatic and vacuolar sequestration of metals reduces the concentration of free ions in the cytosol. Mechanism of cellular sequestration and detoxification of metals comprise cytoplasmatic chelation by thiols (metallothioneins, glutathione and similar oligopeptides) and metal sequestration in the vacuole. Metal coordination within cells of ECMF was recently analysed by Fomina et al. (2007). Hartley et al. (1997) and Meharg (2003) pointed out that ECM and ERM fungi share a long evolutionary history of exposition to toxic metal concentrations, since ECM forests with understoreys of ERM plants cover huge areas with highly acidic soils, and soil acidity increases the concentration of free ions of Al, Fe and Mn. Mechanisms of Al detoxification and of Fe and Mn homeostasis were supposed to confer cotolerance to other metal elements. More particularly, sites with geogeni-cally elevated levels or toxic trace metals are potential hotspots for the evolution of tolerance of certain trace...

Phases of herbicide metabolism

Some herbicides have been shown to undergo bioactivation within plant cells, where a pro-herbicide is converted to a phytotoxic agent by the action of plant enzymes. Before this activation they may be less or non-phytotoxic, so the plant can be instrumental in manufacturing the substance that will eventually kill it. Bioactivation can involve removal of chemical groups that have aided in herbicide uptake and this can have the added benefit of trapping the herbicide within the cell. Herbicide detoxification is achieved by key enzymes that carry out two major functions. First, they alter the chemical structure of the herbicide to render it biologically inert. Second, these reactions serve to increase both the reactibility and the polarity of the herbicide, so that is can be removed from the cytoplasm and either stored in the vacuole or bound to the cell wall. Metabolically, this is achieved by introducing or uncovering polar groups (Phase I metabolism). In some cases polar groups may...

Glutathione Stransferases in fungal infections

Among the enzymes related to GSH metabolism, the role of glutathione S-transferase (GST, E.C. 2.5.1.18) isoenzymes has been the most extensively studied in infected plants. This isoenzyme family has been known since 1970 to have a significant and well-defined role in plant detoxification reactions (Marrs 1996, Edwards et al. 2000). The GST enzymes are homo- or heterodimeric combinations of different subunits. GSTs catalyse the binding of various xenobiotics (including numerous pesticides) and their electrophi-lic metabolites with GSH to produce less toxic and more water-soluble conjugates (Edwards et al. 2000). Besides catalyzing the conjugation of electro-philic compounds to GSH, GST isoenzymes also exhibit peroxidase activity (Bartling et al. 1993) (Figure 3). Various abiotic stress effects are powerful inducers of GST activity in plants (Dixon et al. 1998). Figure 3. The most important reactions catalysed by glutathione S-transferase enzymes in plant cells a) detoxification of...

The Role of the Surface Coat in Immune Evasion by Animal Parasitic Nematodes

Another important group of surface proteins which may act to promote immune evasion in B. malayi are the anti-oxidant products glutathione peroxidase and superoxide dismutase. Bm-GPX-1 is the major 29 kDa surface glycoprotein of adult Brugia (Cookson et al. 1992 Maizels et al. 1989), which is believed to act as a lipid hydroperoxidase, protecting parasite membranes from peroxidation caused by free-oxygen radicals (Tang et al. 1996). A minor surface-associated protein of similar molecular weight is a superoxide dismutase, allowing the parasite to detoxify superoxide radicals (Tang et al. 1994). Many other surface-associated molecules may contribute to immune escape in a less obvious manner. For example, the polyprotein antigen (variously named gp15 400 or Bm-NPA-1) has a very high affinity for fatty acids (Kennedy et al. 1995 Smith et al. 1998) which could sequester substrate required for host leukotriene synthesis. Non-protein filarial products are also likely to play a significant...

UVB Radiation and Signaling Pathways

The UV-B radiation triggers diverse responses involving a differential regulation of the genes and participate in several protective pathways including the DNA repair, detoxification of ROS, and production of secondary metabolites as well as in photomorphogenic events (Agrawal et al. 2009) . The UV-B responses can be elicited with either high fluence (HF-UV-B, over 15 kJ m-2), intermediate fluence (IF-UV-B, 5-7 kJ m-2), low fluence (LF-UV-B, 1-3 kJ m-2), or very low fluence (VLF-UV-B, less than 1 kJ m-2) (Brosch et al. 2002) . However, the exposure of plants to low fluence UV-B promotes the expression of varying genes involved in the UV-B protection, and genes responsible for the production of fla-vonoids and several phenolic compounds, while as the low fluence photomorphogenic responses seem to be initiated by photoreceptors and no alternative UV-B-absorbing molecules seem to mediate the photomorphogenic UV-B responses (Ulm and Nagy 2005) . Also, many components of the protective...

Zinctransporting Genes In Plants

A family of zinc transporter genes that responds to zinc deficiency has also been identified in Arabidopsis. Zn hyperaccumulation in Thlaspi caerulescens is because of the ZNT1 gene, which encodes a high-affinity Zn transporter. This gene is constitutively expressed at a much higher level in T. caerulescens than in T. arvense, where its expression is stimulated by Zn deficiency. In fact, plant Zn status is shown to alter the normal regulation of Zn transporter genes in T. caerulescens. An important aspect of Zn hyperaccumulation and tolerance in T. caerulescens is also the production of low molecular weight compounds involved in Zn detoxification in the cell (cytoplasm and vacuole) and in the long-distance transport of Zn in the xylem vessels.

Glutathione An Ancient Metabolite With Modern Tasks

Glutathione and its homologues comprise a group of tripeptides that are synthesised from the constituent amino acids rather than by direct translation of mRNA. The group of tripeptides is characterised by an N-terminal y-glutamyl moiety, a central cysteine residue, and a variable C-terminal amino acid. Numerous functions have been attributed to glutathione and its homologues that are all connected with its cysteine residue. These functions include storage and transport of reduced sulphur (Herschbach and Rennenberg 1997, 2001), regulation of sulphur nutrition (Herschbach and Rennenberg 1997, 2001), compensation of oxidative stress as chemical anti-oxidant and co-substrate in enzymatic reactions (Noctor and Foyer 1998), redox regulation and buffering (Kunert and Foyer 1993), regulation of enzyme activity, mRNA translation and gene transcription (Fahey et al. 1982, Kunert and Foyer 1993, Foyer and Rennenberg 2000), modification and transport of hormones, and detoxification and transport...

Hmw Pc And Metal Tolerance

Although the accumulation of PCs could be a major component of the heavy metal detoxification process, the increased tolerance to metals may involve other aspects of PC function. The first argument in favor of this came from Delhaize et al. 87 , who observed that, although Cd-sensitive and Cd-tolerant cells of Datura innoxia synthesized the same amount of PCs during the initial 24-h exposure to 250 M Cd, the concentration was toxic to the Cd-sensitive cells only, as revealed by a cell viability study. However, they differed in their ability to form PC-Cd complexes the sensitive cells formed complexes later than the tolerant cells. In addition, the complexes formed by the sensitive cells were of lower molecular weight than those of tolerant cells and did not bind all the Cd, unlike in the tolerant cells. Thus, the rapid formation of PC-Cd complexes sequestering most of the Cd within a short period could be a necessity for plants or cells showing tolerance to heavy metals. Evidence in...

Glutathione Peroxidase Glutathione Stransferase Glutathione Reductase

The selenoprotein glutathione peroxidase (GPX) detoxifies H202 in animal tissues but an equivalent reaction is not found in plants. Plant GPXs are not constitutive but are induced in response to stress. They do not contain selenium and do not catalyse the GSH-dependent reduction of H202 (Eshdat et al. 1997). In plants ascorbate peroxidase (APX) and catalase (CAT) detoxify H202 while GPXs have more sophisticated roles, including the removal of lipid and alkyl peroxides (Kranner and Grill 1996, Eshdat et al. 1997). Kranner and Grill (1996) suggested that GPXs may be involved in the GSH-dependent regeneration of In addition, GSTs can function to remove lipid peroxides and fulfil a peroxidatic role (Bartling et al. 1993, Cummins et al. 1999). Oxidative stress induces specific GST isoforms and GPXs whose role is to detoxify lipid peroxidation products. Transgenic tobacco lines overexpressing plant GST Gpx were reported to show enhanced antioxidant capacity and substantial improvement in...

Plant Responses to Cadmium

Cadmium can be categorized into different protein groups in terms of photosynthetic processes, signal transduction, and transcriptional regulation, cellular defenses, ROS detoxification and repair, hydric balance, metal transport, cell wall metabolism, sulfate and GSH metabolism and protein degradation. 5.3 Cellular Detoxification and Repair Several genes associated with cellular detoxification and repair have been shown to be induced by treatment with cadmium. Chitinases and heat shock proteins (HSPs) are induced in response to heavy-metal stress and are regarded as a second line of defense under these stress conditions (Metwally et al. 2003 B k siov et al. 2008 Rodr guez-Serrano et al. 2009 Zhao et al. 2009). Transgenic plants expressing fungal chitinases actually showed enhanced tolerance to metals (Dana et al. 2006) , while chitinase isoforms are differentially modified by certain metals (B k siov et al. 2008) . Chitinases are regulated by ROS and are possibly part of the general...

Other Metal Chelating Agents Thiol Peptides

Another group of agents with metal-chelating properties has been described in some species of ECM fungi, but unlike siderophores and LMW organic acids, they are more related to detoxification mechanisms than to metal ion nutrition or mineral solubilization. This group includes MTs, PCs, and GSH, all the thiol peptides (Gadd 1993 Meharg 2003 Pocsi et al. 2004 Bellion et al. 2006). These peptides act intracellularly once the metal ions have entered the cell, they regulate or prevent the activity of metal ions in the cytosol through complexation. Thus, unlike siderophores and LMW organic acids that can represent avoidance mechanisms in relation to metal detoxification, these peptides represent intracellular detoxification mechanisms. PCs are peptides rich in Cys, with a general (g-Glu-Cys)n-Gly (n 2-11) structure, of low molecular weight, which in fungi does not seem to exceed 2 kDa. Unlike MTs, PCs are not codified in the genome and their presence has been shown mainly in plants, where...

Localization of Heavy Metals in Cells and Tissues of Different Plant Organs

Rejective Way Silicon Uptake

As shown in Fig. 2, general mechanisms for detoxification and accumulation of heavy metals in plants are the distribution of the metals to apoplastic compartments like cell walls or trichome, and the chelation of the metals by a ligand in cytoplasm, followed by the sequestration of the metal ligand complex into the vacuole, in the different organs such as roots, stems and leaves (Yang et al. 2005). Generally, the heavy metal contents in plant organs decrease in the following sequence root leaves stems inflorescence seeds. However, this order sometimes varies with plant species, especially in hyperaccumulators, of which the shoots have the highest heavy metal content. Roots usually manifest the maximum content of heavy metals. Leaves vary with age in their ability to accumulate heavy metals, some heavy metals accumulate preferentially in the youngest leaves of plants, whereas in others, the maximum content is found in senescing leaves. Preventing Cd ions from entering the cytosol by...

How treated plants die

A striking feature of the ALS inhibitors is their highly selective action at low dosage. Indeed, some cereals have been reported to tolerate up to 4000 times more chlorsulfuron than some susceptible broadleaf species. Various studies have shown that this extreme species sensitivity is not due to herbicide uptake, movement or sensitivity to ALS, but is correlated to very rapid rates of metabolism in the tolerant crop. In the tolerant crop soybean the degradation half-life of triazolopyrimidines has been shown to be 49 hours compared to 165.3 hours in the susceptible species pitted morning glory (Swisher et al., 1991). Several sites on the sulphonylurea molecule are locations for enzyme attack and more than one enzyme system has been demonstrated to be active in their detoxification, as summarised in Figure 9.8 (Beyer et al., 1987). This extreme species sensitivity may have dramatic consequences to a following crop in the same land. For example, since wheat is more than 1000 times more...

Herbicide safeners and synergists

Sorghum Safeners

As some safeners may show structural homology with herbicides, it was previously thought that they competed with the herbicide molecule for the target site. We now know, however, that their protective effect results from a general enhancement of detoxification processes, including the induction of Since a crop has to show some degree of tolerance to the herbicide for it to be safened, it would appear that the process is a 'top-up' mechanism for detoxification routes that are already operative. Despite considerable interest in safeners, their activities have mainly been demonstrated in monocotyledonous crops, notably maize, wheat, sorghum and rice. It is likely that the identification of genes encoding safener-inducible enzymes will allow their transfer to give genetically modified crops with an enhance ability to detoxify herbicides. This approach has already shown potential (Davies and Caseley, 1999), although further development will require a greater public acceptance of GM crops...

Effect of Heavy Metals on Plants

Lue-kim and Rauser (1986) reported an induction of Cd-binding protein from crude extracts of roots of tomato with an apparent molecular weight 31,000 Da in high ionic strength and 21,500 Da at low ionic strength. Increase in soluble protein was also reported by Vogeli-Lange and Wagner (1990) in tobacco leaves on Cd exposure at a concentration of 20 mm. Lozano-Rodriguez et al. (1997) observed an increase in the soluble protein content of pea root and shoot upon treatment of Cd at a concentration of 0.05 mM, whereas the same had no effect on maize. Ali et al. (1998) have observed an increase in the protein content of Bacopa monniera plant-lets on exposure to Cd stress. Hirt et al. (1989) reported stimulation of the protein and RNA synthesis in suspension cells of Nicotiana tabacum on exposure to Cd stress at a concentration of 100 mM. They observed that the increase in protein content was probably due to the synthesis of new proteins to detoxify the intracellular Cd by binding with the...

Grazing Deterrent Effect and Toxicity of Various Lichen Compounds

There are few studies quantifying the herbivory-deterrent effect and or toxicity of specific lichen compounds for herbivores. Table 2 summarizes documented antiherbivore and toxic effects of lichen compounds. Removal of secondary compounds from Vulpicida pinastri and from H. physodes greatly increased survival of larvae of the moth E. depressum, whereas acetone rinsing of Parmelia sulcata had no long-term impacts on the larvae (Poykko et al. 2005). These data indicate that vulpinic and pinastric acids from V. pinastri, and, e.g., physodic acid and or physodalic acid from H. physodes are more toxic for the larvae than atranorin that is present in both H. physodes and P. sulcata. For all these three lichen species, the moth larvae preferred acetone-rinsed thalli. In total, such results indicate that some substances such as pinastric and physodic acid are both toxic and deterrent to moth larvae, whereas atranorin and or salazinic acid (present in P. sulcata) mainly is deterrent (Poykko...

Physical Chemical Barriers and Evasion Behavior

Primary defense in nematodes is provided by the multi-layered cuticle, which offers a superb physical barrier against external aggressions. Secondly, they are equipped not only with a muscular grinder that breaks down bacteria but also with an intestine which generates an environment hostile to microbial colonization. A complete transcript inventory of the C. elegans intestine reveals an arsenal of secretory proteins with roles in bacterial digestion (lysozymes, saposins, lipases, lectins and proteases), detoxification and stress responses (thaumatin-like, ABC transporters) (McGhee et al. 2007). Furthermore, the worm has a sophisticated chemosensory system, which enables it to sense different bacteria and to learn how to discriminate between innocuous and pathogenic microbes (reviews by Schulenburg and Boehnisch 2008 Zhang 2008). For an organism that lives in decaying matter and feeds on microorganisms, an efficient pathogen avoidance behavior appears to be one of the best strategies...

Carbohydrates And Related Compounds

Vital nutritional role and transport of energy (as sucrose). Carbohydrates also serve as a structural material (hemicellulose, cellulose), as a component of the energy transport compound ATP, recognition sites on cell surfaces, one of three essential components of DNA and RNA and plant glycosides. They also play a number of ecological roles, in plant-animal interactions (flower nectar is mainly sugars), in protection from wounds and infections, and in the detoxification of foreign substances. The major simple sugars present in plants are the monosaccharides glucose and fructose and the disaccharide sucrose (Loewus and Tanner, 1982 Dey, 1990). There are traces of galactose, rhamnose, xylose and sugar phosphates involved in metabolism. Sugar phosphates are very easily hydrolyzed during the manipulation, thus special procedures are required to detect them. The bulk of carbohydrates present in plants are in bound form, mainly as oligo- and polysaccharides, or bound to different aglycones,...

Sources of ROS in Plants Exposed to Cadmium

Cadmium Plant

The reactive oxygen species are mainly singlet oxygen ('O2), superoxide radical (O2-), hydroxyl radical ( OH) and hydrogen peroxide (H2O2) which are by-products of normal aerobic metabolism such as respiration and photosynthesis. Their steady-state levels are determined by the interplay of different ROS-producing and ROS-scavenging mechanisms. This balance is maintained by enzymes such as superoxide dis-mutase (SOD), which remove O2- radicals, and catalase (CAT), peroxidase (POX), and peroxire-doxin, which decompose H2 O2 and use metabolites such as glutathione (GSH) and ascorbate (ASC), to control ROS accumulation in different subcellular compartments. An excess of ROS is dangerous mainly because of reactions with lip-ids, proteins, and nucleic acids, giving rise to lipid peroxidation, membrane leakage, enzyme inactivation and DNA breaks or mutations, which can cause severe damage to cell viability. Subtle control of ROS production enables these species to act as signaling molecules...

Mechanized agriculture usually necessitates the use of herbicides

Some herbicides are taken up only by the roots and others by the leaves. To keep the railway tracks free of weeds, nonselective herbicides are employed, which destroy the complete vegetation. Nonselective herbicides are also used in agriculture, e.g., to combat weeds in citrus plantations. In the latter case, herbicides are applied that are only taken up by the leaves to combat herbaceous plants at the ground level. Especially interesting are selective herbicides that combat only weeds and effect cultivars as little as possible (sections 12.2 and 15.3). Selectivity can be due to different uptake efficiencies of the herbicide in different plants, different sensitivities of the metabolism towards the herbicide, or different ability of the plants to detoxify the herbicide. Important mechanisms that plants utilize to detoxify herbicides and other foreign compounds (xenobiotics) are the introduction of hydroxyl groups by P-450 monooxygenases (section 18.2) and the formation of glutathione...

Metal Transporters in Hyperaccumulators

Homeostasis Plant

Fig. 1 Molecular and physiological mechanisms involved in Cd hyperaccumulation and detoxification (a-d), and their evolutionary significance for Cd hyperaccumulators (e-g). (a) Root foraging for Cd is a strategy that hyperaccumulator species employ to acquire high levels of Cd in Cd-enriched patches in a heterogeneous substrate, (b) In the root, uptake of Cd ion is mediated by various metal transporters residing in the plasma membrane, (c) Cd is transported to Fig. 1 Molecular and physiological mechanisms involved in Cd hyperaccumulation and detoxification (a-d), and their evolutionary significance for Cd hyperaccumulators (e-g). (a) Root foraging for Cd is a strategy that hyperaccumulator species employ to acquire high levels of Cd in Cd-enriched patches in a heterogeneous substrate, (b) In the root, uptake of Cd ion is mediated by various metal transporters residing in the plasma membrane, (c) Cd is transported to Fig. 1 (continued) the shoot via the xylem through either the...

Ferritin Overexpression In Transgenic Plants And Its Consequences

Iron and oxygen metabolisms can interact to promote oxidative stress. Therefore, Fe sequestration in ferritin of transformed plants could have a beneficial effect against Fe-mediated oxidative stress. Methylviologen, the active molecule of the herbicide paraquat, acts by promoting an oxidative stress in the chloroplast, leading to proteolysis, lipid peroxidation and ultimately to cell death (Dodge, 1994). The toxic effect of methyl viologen requires free Fe to take place, and can be antagonized by Fe chelators such as desferrioxamine (Korbaschi et al., 1986 Zer et al., 1994). Indeed plants overexpressing ferritin are more resistant to methylviologen toxicity, confirming that the transgenic ferritins were functional in vivo - i.e. able to sequester Fe atoms (Deak et al., 1999 Van Wuytswinkel et al., 1999). However, it has been documented in animal cells, that ferritin can act either as anti- or pro-oxidant (Cairo et al., 1995). Therefore, the increased resistance to paraquat treatment...

Chemical Features of Urban Soils

Urban soils show chemical human impacts compared with natural soils their pH, element cycling and nutrient availability are altered. Their node function as nutrient source and buffering system or as detoxification medium is restricted or imbalanced. Fertilizer or compost application, atmospheric pollution and outwash via stem-flow, heavy metal contamination from various sources, de-icer from winter maintenance, contaminated irrigation-water, debris from exotic species, litter removal etc. contribute to chemical deviations from the natural element budgets and have additive or antagonistic effects.

Bioconversion Of Ergot Alkaloids As A Tool For Study Of Their Metabolism In Mammals

Elucidation of mammalian metabolic pathways is important in attempting to rationalise detoxification, and to evaluate potentially active metabolites. In case of some ergot alkaloids with strong hallucinogenic activity (e.g. LSD) it is desirable to detect its metabolites for use in anti-doping screening and forensic chemistry. However, such studies have been hampered by a lack of minor metabolite availability. For this reason, Ishii et al. (1979a, b, 1980) examined a series of microorganisms and animals for parallel routes of metabolism of LSD and of the related compounds. They assumed that the metabolism of these xenobiotics would proceed in a similar manner in both mammals and microorganisms (Ishii et al., 1980). Both nor-LSD and lysergic acid ethylamide produced by the microbial conversion of LSD are known metabolites of LSD in mammals, and the authors were able to use the lysergic acid ethylvinyl amide generated in the microbial studies to determine its pr sence in mammals. Ergot...

Chelation at Cytoplasm and Vacuole Level

Chelation in the cytoplasm is an intracellular buffer system to control PTE toxicity through reduction of the concentration of cytotoxic-free PTE ions. In this system, metallothioneins (MT), metal-binding polypeptides, and or MT-like proteins may be involved. In contrast to ectomycorrhizal fungi, the participation of these compounds in metal detoxification has not been confirmed in AMF 69,70 . However, evidence suggesting the presence of Cd-binding thiols in AMF as well as high concentrations of N and S in mycorrhizal roots exposed to Cd have been reported 71,72 . Galli et al. 72 studied the effect of Cu on the uptake, amount, and composition of Cu-binding peptides (Cu-BPs) of mycorrhizal maize plants inoculated with Glomus intraradices. They observed increased concentrations of the thiols cysteine, y-glutamylcysteine, and glutathione up to an external Cu supply of 9 g g-1. However, the amount of thiols in Cu-BPs was not increased by mycorrhizal colonization in Cu-treated plants and...

Role of GST activity in infected plants

Tmv Xanthi Tobacco

Summarizing the above reports on GST, it seems that the role of GSTs in infected plants is the suppression of necrotic disease symptoms by the detoxification of toxic lipid hydroperoxides that derive from peroxidation of cell membranes. In the future, this supposition may be confirmed by the study of transgenic plants overexpressing GST isoenzymes and of transformants expressing GSTs in antisense direction. Tobacco plants have been transformed with genes encoding GST (Roxas et al. 1997, Thompson et al. 1998). These transgenic tobacco plants overexpressing GST were more resistant towards abiotic stress effects than wild type plants. The effects of microbial infections on these transgenic plants have not been reported yet.

Supplementation on Plants Stress Responses

High temperature stress can cause premature leaf senescence, an internally programmed degeneration process that leads to tissue death. High temperature stress directly damages the photosynthetic apparatus and decreases both photosynthetic rate and duration of the assimilate supply and promote accumulation of ROS in the chloroplast, particularly when the antioxidant capacity to detoxify ROS is low (Prasad et al. 2008). Foliar application of Se increased antioxidative function as demonstrated by increased activity of SOD and reduced O2 concentration in the high-temperature stressed plants (Djanaguiraman et al. 2010) . Selenium application exerted its positive influence under high temperature stress by increasing net CO. assimilation and decreasing H2O2 content, MDA production, and membrane injury (Fig. 16.7).

Traditional Chinese Medicine

Herbs with the property of cold or cool are able to clear heat, to purge the pathogenic fire and to detoxify, and can be used to treat heat syndromes. For example, Artemisia herb (A. annua) and Coptis root (Coptis cbinensis) are cool in nature and are used to treat internal heat caused by bacterial infections or by noninfectious disease. However, these two herbs are not necessarily inter-changeable in their usage because they are different in other respects. Herbs with the property of warm and hot are able to warm internally, to expel cold and to tonify Yang, and are thus used to treat cold syndromes. For example, ginger (Zingiber officinale), and cinnamon bark, (Cinnamomum cassia) are hot in nature and are commonly

Organic Acids Nicotianamine Amino Acids and Phytates

Plant cells contain many other small organic ligands with variable functional groups, including amino acids, polyamines, nucleotides, phytates and other phosphate sugars. Of these, polyamines appear to act as a messenger or a molecule to stabilize or protect the cell membranes rather than as direct binding ligands to toxic heavy metals (Sharma and Dietz 2006). Nucleotides, phytates and sugar phosphates can conjugate to Ca, Mn, Mg, Al and other metals through their O-bonds. Especially, the importance of phytates in coordination and storage of phosphate and metals such as Zn, Mg, and K in vacuole and cytoplasm and also in the detoxification of Cd has been widely suggested (Van Steveninck et al. 1992 Hayden and Cobbett 2006). Amino acids are the most abundant amphoteric ions with variable forms and residues, existing in 10-100 mM orders of concentrations and serving multiple functions in plant cells. Cysteine (Cys) is a thiol compound that has a S-donor residue equivalent to a GSH...

Oxidative Stressrelated Proteins In Nodules

Cognex Sight 7010

Induction of increased levels of ROS has been demonstrated in response to abiotic stress caused by high light at low temperatures (Nakano et al., 2006), and exposure to heavy metals. Continuous exposure of root nodule to abiotic stress increases the level of several metabolites, proteins with known enzymatic or structural functions and regulatory proteins that may provide a certain degree of tolerance. Stress-induced proteins include key enzymes for osmolytes (proline, betains, sugars such as trehalose and polyamines) biosynthesis, detoxification enzymes, water channel and transport proteins and these may be targeted as the active components available for manipulation. Identification of the precise physiological roles of most stress genes proteins has proved to be a challenging task. There is a need to eliminate effectively the ROS generated as a result of environmental stresses in aerobic organisms. However, ROS are also generated in nodules during normal...

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