Natural Antioxidants

Antioxidant Defence for Abiotic Stress Tolerance

The harmful effects of ROS are prevented by the presence of lipid soluble antioxidants (a-tocopherol and carotenoids), water-soluble reductants (glutathione and ascorbate) and antioxi-dant enzymes such as catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11) and superoxide dismutase (SOD, EC 1.15.1.1) present in plant cells (Desikan et al. 2004). In response to stress, some of the osmolytes accumulate in plant 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...

Nonenzymatic Antioxidants 331 Ascorbic Acid

Among the small molecular antioxidants in plants, ascorbate is most abundant and is most concentrated in leaves and meristems (reviewed by Ahmad et al. 2010b) . It is about five to ten times more concentrated than GSH in leaves (Ishikawa et al. 2006) . AsA is present in high concentration in fruits, especially citrus fruits, but the concentration in fruits is not always higher than in leaves (Davey et al. 2000). Some fruits such as blackcurrants and rose hips are famous for their exceptionally high ascorbate content (Ishikawa et al. 2006). AsA occurs in all subcellular compartments, and the concentration varies from 20 mM in the cytosol to 300 mM in chloroplasts (Noctor and Foyer 1998). The synthesis of AsA takes place in mitochondria and is transported to other cell compartments through a proton electrochemical gradient or through facilitated diffusion (Horemans et al. 2000). Franceschi and Tarlyn (2002) reported the presence of ascorbate in the phloem sap of A. thaliana. Other...

Antioxidants as a Protective Means

Radiation and oxidative damage have always been common on Earth (Rothschild and Mancinelli 2001). When cells are desiccated in the light, chlorophyll molecules continue to be excited, but the energy not used in carbon fixation will cause formation of singlet oxygen (Kranner et al. 2005). Photoprotective mechanisms can dissipate much of it. These mechanisms include dissipation as heat via carote-noids, photorespiration, and morphological features that minimize light absorption. ROS such as superoxide and singlet oxygen are produced in chloroplasts by photo-reduction of oxygen and energy transfer from triplet excited chlorophyll to oxygen, respectively. In addition, hydrogen peroxide and hydroxyl radicals can form as a result of the reactions of superoxide. All these ROS are reactive and potentially damaging, causing lipid peroxidation and inactivation of enzymes (Smirnoff 1993). Free radical scavengers are the two water-soluble antioxidants reduced glutathione (GSH) and ascorbate...

ROS Signaling and Antioxidant Responses

Fig. 3 Major physiological changes described in plants treated with heavy metals (HM2+). In excluder plants metals accumulate in the root, where most of the alterations occur. The cell wall can act as a sink, but when this barrier is overridden, metals enter the protoplast probably through ion channels (for example Ca2+-channel). Part of the uptaken metal can be expelled by transporters of the HMA, possibly loading them in the xylem. Plasma membrane NADPH-oxidases are activated to generate O2 , which is converted to H2O2 in the apoplast to serve as substrate of cell wall peroxidises to stiffen cell wall polymers. H2O2 can also oxidize membrane lipids, generating peroxide lipid radicals (FA-OO ), or permeate to the cytoplasm where antioxidant enzymes must control cellular levels of ROS (SOD, CAT and APX). On the other hand, metals would activate phytochelatin synthase (PCS) triggering the synthesis of phytochelatins (PC). These biothiols would form complexes that are thought to be...

Antioxidant Systems Under Cd Stress

5.2.1 Enzymatic Antioxidants Systems A variety of proteins function as scavengers of ROS such as superoxide dismutase (SOD), catalase (CAT), enzymes of the ascorbate-glutathione cycle, peroxiredoxin and thioredoxin families. The main response for the removal of ROS appears to be via the induction of SOD and CAT activities, and by the induction of GR to ensure the availability of reduced glutathione for the synthesis of Cd-binding peptides. This fact could be related to the inhibition of APX activity probably due to glutathione and ascorbate depletion (Gomes-Junior et al. 2006). Different effects were observed in antioxidant enzymes depending on Cd concentration, period of treatment, the plant tissue studied and the plant itself. SOD plays an important role as a defence mechanism carrying out the catalytic dismutation or disproportionation of O2 - with production of water and hydrogen peroxide. While Cd-dependent reduction of SOD activity has been reported in wheat (Milone et al. 2003)...

C ROS Antioxidants Jasmonic Acid and Ethylene

JA signaling for response to wounding of plants has been suggested to be mediated by H2O2 which, in turn, stimulates gene expression in the vicinity of the wound site that could help prevent opportunistic infections, deter herbivores, and repair wounds (Orozco-Cardenas et al., 2001). JA pre-treatment of plants can also protect tobacco and Arabidopsis against ozone damage, an effect that may, in part, be due to changes in expression of antioxidant defense genes such as APX (Orvar et al., 1997 Rao et al., 2000). Similarly, a coordinated regulation of the expression of genes of glutathione metabolism such as glutathione reductase (GR) and the enzymes of glutathione synthesis occurs upon treatment of Arabidopsis plants with JA (Xiang and Oliver, 1998). It is not clear that all these effects of JA on ROS antioxidant metabolism are linked, but if they are, then those of the whole plant response to environmental challenges that are influenced by JA must involve a coordinated regulation of...

Growth ROS Antioxidants and Auxins

The induction of defense responses can also lead to a down-regulation of genes associated with the vegetative growth of the plant. For example, in the vtcl mutant, a slow growth rate has been attributed to elevated levels of ABA rather than partial depletion of its ascorbate content (Pastori et al., 2003). Furthermore, H2O2 treatment of Arabidopsis protoplasts led not only to MAPK-mediated up-regulation of antioxidant defense gene expression, but also to a down-regulation of auxin-regulated genes that might be implicated in meristem growth (Kovtun et al., 2000). This may reflect a recently described convergence of kinase-mediated signaling that would coordinate both defense and growth responses to H2O2 (Moon et al., 2003). Conversely, auxin treatment of plant tissues may induce ROS production and also induce expression of antioxidant defense genes such as GSTs (Chen and Singh, 1999 Joo et al., 2001 Pfeiffer and Hoftberger, 2001). Again, these data indicate that there is a two-way...

Flavonoids as Antioxidants in Plants Under Abiotic Stresses

Flavonoids make a relevant contribution to the response mechanisms of higher plants to a plethora of abiotic stresses. In addition to the long-reported functions as screeners of damaging short-wave solar radiation, flavonoids have been suggested as playing key functions as antioxidants in stressed plants, by inhibiting the generation and reducing reactive oxygen species (ROS) once formed. The ROS-scavenging properties of flavonoids are restricted to few structures, namely, the dihydroxy B-ring-substituted fla-vonoid glycosides. This structure-activity relationship conforms to the well-known stress-inducedpreferentialbiosynthesis ofdihydroxy B-ring-substituted both flavones and flavonols. These flavonoids, especially the derivatives of quercetin, have been shown to greatly affect the movement of auxin at intra-and intercellular levels, and hence to tightly regulate the development of individual organs and the whole plant. The effectiveness of flavonoids to inhibit the activity of the...

Down Regulation of the Antioxidant Network Evidence from Lesion Mimic Mutants

In addition to ROS production, and of more relevance to this chapter, there could arguably be a down-regulation of expression of key enzymes of the antioxidant network which would point to coordinated control and therefore cross-talk between pathways. A good example of this concept may be the mode of action of LSD1. The prefix LSD means lesion simulating disease and refers to the way in which the gene was first identified in Arabidopsis. The mutant lsd1 is one of a number of so-called lesion mimic mutants identified in several plant species that either show spontaneous but discrete HR-like lesions when not exposed to a pathogen, or lethal, spreading, uncontrolled lesion formation under non-permissive conditions. Such environmental conditions include a change in the light environment, exposure to an avirulent pathogen, or to ozone (Dietrich et al., 1994 Bowling et al., 1997 Gray et al., 1997 Takahashi et al., 1999 Overmyer et al., 2000 Devadas et al., 2002). LSD1 is a regulatory...

Free Radicals Active Oxygen Species and Antioxidants

The highly reactive free radicals, along with hydrogen peroxide (H2O2), are collectively termed active reactive oxygen species (AOS ROS). While the intracellular glassy state must curtail molecular and AOS mobility, and thus interaction, during the process of desiccation, intracellular structures are highly vulnerable as conditions for radical generation are enhanced (Vertucci and Farrant, 1995 Pammenter and Berjak, 1999 Walters et al., 2005a). Possession and effective operation of a suite of antioxidants is of prime importance during dehydration of orthodox seeds, and again as soon as water uptake commences by the desiccated cells (Pammenter and Berjak, 1999). Additionally, non-enzymic antioxidants are likely to confer protection during the desiccated state in seeds (Bailly, 2004) and in the cells of any organism or structure capable of surviving extreme desiccation. Most studies on AOS and antioxidants have been focused on the final stages of seed desiccation, but in his review...

Drought Stress Induced Reactive Oxygen Species and Antioxidants in Plants

Aerobic metabolism in plants results in the generation of reactive oxygen species (ROS). ROS are produced constantly in plants under physiological steady state condition, and plants have evolved to efficiently scavenge and maintain the levels of ROS at non-damaging levels. However, plants when exposed to either abiotic or biotic stress conditions, the production of ROS exceeds their scavenging capacity, leading to an outburst of highly reactive oxidative species capable of inflicting significant damage to the membranes, DNA, and proteins. On the other hand, these reactive molecules when maintained under non-damaging levels are useful signalling molecules involved in relaying stress signal to activate acclimation and defence mechanism. Drought or water deficit stress is one of the major abiotic stresses which induces the production of different kinds of ROS including both free radicals such as superoxide (O2-), hydroxyl radicals (OH), per-hydroxy radical (HO2) and alkoxy radicals (RO)...

Ginger as an Antioxidant

Ginger has a high content of antioxidants and has been grouped as one of the spices with good antioxidant activity, with 1.8 index rating (Chipault et al., 1952). This makes it a free radical scavenger (Lee and Ahn, 1985). Sethi and Aggarwal (1957) reported that dried ginger has weak antioxidant properties. The antioxidant property of ginger in comparison with other common spices is given in Table 15.8. Fugio et al. (1969) studied the antioxidant properties of the chemical components of many spices and found that the shogaol and zingiberene found in ginger exhibited strong antioxidant activities. The antioxidant activity of ginger is dependent on the side-chain structures and substitution patterns on the benzene ring. Twelve compounds showed higher activity than a-tocopherol. Mainly, the antioxidant activity is exerted by gingerol

Antioxidant Flavonoids and the Antioxidant Machinery of Plants

3.1 Stress-Induced Alterations in the Antioxidant Enzymes System There is a large consensus that a well-coordinated system of constitutive antioxidant defenses is activated in plants upon a plethora of abiotic stresses (for a recent review, see Gill and Tuteja 2010). Superoxide dismutase (SOD), the well-known first-line of defense against ROS generation (aimed at removing the highly reactive superoxide anion) (O2-), and both ascorbate peroxidase (APX) and catalase (CAT), the enzymes that are devoted at detoxifying the relatively stable H.O2, have long been reported to play a key role in protecting plants from stress-induced oxidative injuries (Schwanz and Polle 2001a, b Polle 2001). The extent to which the activity of antioxidant enzymes increases upon stress imposition has been widely reported to correlate positively with tolerance to various abiotic stresses (Hern ndez et al. 1999, 2000, 2003 Tattini et al. 2005 Sekmen et al. 2007), although it has been also reported that the...

Effects of Pomegranates on Antioxidant Status

Pomegranate anthocyanins have been shown to scavenge superoxide (O -) and hydroxyl (Off ) radicals to prevent lipid peroxidation in rat brain homogenates.16 An extract from pomegranate peel fed to rats for 14 days reduced lipid peroxidation in the liver as well.41 The plasma antioxidant status of humans fed pomegranate juice is elevated over control subjects,42-44 suggesting that pomegranate polyphenols are bioavailable and are able to elevate the antioxidant capacity of the body. Pomegranate polyphenols have been shown to increase the concentrations of the endogenous antioxidant glutathione (GSH) in mouse peritoneal macrophages,42 while pomegranate peel extract, fed to rats for 14 days, prevented the carbon tetrachloride-induced loss of peroxidase, catalase, and superoxide dismutase in the liver.41 GSH is the major antioxidant system in cells, donating electrons to H2O2 and becoming oxidized to GSSG in a reaction catalyzed by glutathione peroxidase. Intracellular antioxidant content,...

Nutritional Antioxidants And Polyphenolic Flavonoids

The beneficial health effects attributed to the consumption of fruits and vegetables are related, at least in part, to their antioxidant activity.12 Edible plants contain several hundred different antioxidants.3 Natural antioxidants include vitamins C and E, carotenoids (such as P-carotene and tomato's lycopene), and polyphenolic fla-vonoids (such as those present in grapes, berries, licorice, ginger, nuts, and olive oil). For a compound to be defined as an antioxidant it must satisfy two basic conditions Low-density lipoprotein (LDL) oxidation is considered to be a hallmark of early atherogenesis. Nutritional antioxidants can affect LDL oxidation directly or indirectly, via modulations of arterial wall cell oxidative state and its subsequent capacity to oxidize LDL. Dietary antioxidants can inhibit LDL oxidation by several means 1. Scavenging of free radicals, chelation of transition metal ions, or protection of the intrinsic antioxidants in the LDL particle (vitamin E and...

The Level of Free Radicals Defines the Type of Plant Reaction

Low levels of free radicals are apparently able to stimulate animal macrophages and neutrophils (Finkel 1998). Such role of radicals is not established for plants however, ROS also play a critical role in the initiation and maintenance of a hypersensitive response upon an encounter with a pathogen. Thus, we hypothesized that pretreatment of plants with oxidative stress-generating compounds would prime them to tolerate a higher level of stress. Since it was not clear what level of oxidative stress is required to generate such response, we first attempted to identify the optimal external concentration of RB that would be used for pretreatment. Seedlings at 2 weeks post-germination were incubated for 2 hours in medium containing 0.02 iM, 0.1 iM or 0.5 iM RB and then were transferred to liquid medium containing 20 M or 50 M of MMS. These concentrations of MMS were previously shown to induce HRF (Puchta et al. 1995). Interestingly, it was observed that pretreatment with 0.5 M RB...

Conclusions on Hormone Signaling and ROSAntioxidant Metabolism

It is clear from the above considerations that antioxidant metabolism can be profoundly influenced by, and in turn influence, signaling pathways nominally directed by one or more hormones. It has been suggested by many authors that the overlap in the type of genes induced by chemically diverse molecules may be reconciled by invoking a common effect on ROS at the cellular level (reviewed in Garreton et al., 2002). However, it is also clear that, in all cases, complex feedback regulation occurs by which ROS and antioxidants can influence the potency of hormones, especially those associated with stress. Thus, circular pathways of regulation have to be invoked to link up these diverse observations (e.g. Overmyer et al., 2000). Perhaps the most compelling part of the relationship between cellular redox state (influencedby antioxidants such as glutathione) and signaling pathways is that key players in the pathways studied to date have either been shown to be or may be redox regulated. These...

Effect of Ethylene on the Antioxidant System during Leaf Senescence

The oxidative metabolism has an important role at cellular level when senescence takes place. During leaf senescence there is an overproduction of reactive oxygen species (ROS) such as superoxide anion (O2-), hydroxyl radicals (OH'), hydrogen peroxide (H2O2) and singlet oxygen (1O2) that may cause damage and cell death. However, they are also products of the normal enzymatic reactions in peroxisomes, glyoxysomes, and chloroplasts. The harmful ROS are controlled and balanced by the antioxidant systems present in leaves. The leaf cells act as a defense response against the accumulation of ROS by increasing catalase (CAT) and superoxide dismutases (SOD) activity. But other enzymatic and non-enzymatic antioxidants are also involved, such as ascorbate, reduced gluthatione (GSH), a-tocopherol and carotenoids (Foyer et al. 1994 Bartoli et al. 1996 Hodges et al. 1996, 1997a, 1997b). The ascorbate-glutathione cycle, also known as the Asada-Halliwell cycle, is the most important antioxidant...

Glutathione and Antioxidant Defense

Even in the absence of an enzyme, glutathione is able to interact rapidly with free radicals such as superoxide and the hydroxyl radical (Polle, 2001). In addition, glutathione plays an important role in peroxide detoxification through several possible enzyme systems. First, GSH can regenerate ascorbate (Fig. 1), either directly or through the action of various enzymes able to catalyze DHA reduction, including glutaredoxins (GRX) and GSTs (Wells et al., 1990 Trumper et al., 1994 Shimaoka et al., 2000 Urano et al., 2000 Dixon et al., 2002). Secondly, both GRX and GSTs can also reduce hydroperoxides to the corresponding alcohol or H2O (Bartling et al., 1993 Collinson et al., 2002). Third, certain PRXs are regenerated by a GR GRX system (Rouhier et al., 2002). Fourth, specific glu-tathione peroxidases (GPXs) exist in plants (Eshdat et al., 1997). Genes encoding plant GPXs have been

Antioxidant Metabolites

Next to GSH, several other metabolites participate in the cellular antioxidant network to combat an increased ROS accumulation during metal stress. In the following paragraphs, these metabolites and their potential involvement in the oxidative challenge mediated by Cd and Cu are discussed. In plants, AsA has a regulatory role during cell growth, cell wall biosynthesis, photosynthesis and cell differentiation. This metabolite is present in all subcellular compartments including the apoplast, chloroplast, cytosol, vacuoles, mitochondria and peroxisomes. In chloroplasts and mitochondria, AsA plays a key protective role by decreasing the damage caused by ROS formed during photosynthetic and respiratory processes (Potters et al. 2002). Ascorbic acid directly reacts with all different ROS (1O2, O2- , H2O2, -OH) in which AsA is being oxidised (Fig. 2). As mentioned above, the oxidation reduction ratio of AsA reflects the cellular toxicity level in Cd- and Cu-exposed plants. Besides its role...

Reconfiguration of the Antioxidant Network and the Regulatory Role of Glutathione

There are numerous studies on a wide range of plant species, both in the natural environment and under laboratory conditions, showing that successful acclimation is associated with changes in antioxidant defenses (Rauser et al., 1991 De Vos et al., 1992 Walker and McKersie, 1993 Chaumont et al., 1995 Kampfenkel etal., 1995 Iturbe-Ormaetxe etal., 1998 Bruggemann et al., 1999 Hernandez et al., 2000). During the life of a plant, one may expect that antioxidant defenses will undergo subtle adjustments, with some components increasing their levels or activity, while others are decreasing. Recent evidence for this comes from the study ofan Arabidopsis APX1 null mutant, in which only a mild growth diminution was apparent that was accompanied by alterations in the expression of an-tioxidant defense genes as well as a range of genes involved in many other cellular functions (Pnueli et al., 2003). Similar observations have been made in transgenic tobacco with suppressed cytosolic APX...

Plant Antioxidant Systems

Oxygen reactivity strongly influenced the evolution of aerobic organisms making necessary efficient strategies allowing cells to cope with the inevitable ROS production in their metabolism. This led to the development of a complex and redundant antioxidant network in all aerobic cells. The term antioxidant is referred to metabolites, such as ascorbate, glutathione, pyridine nucleotides, which are present in concentrations lower than oxidizable substrates but which can prevent or and revert their oxidation. These metabolites are involved in network of reactions in which several enzymes control their biosynthesis and redox state or utilize them as reducing substrates for ROS detoxification. These networks define the capability of a specific antioxidant metabolite to counteract ROS production and to control their levels. They act in synergy with enzymes, such as superoxide dismutase (SOD) and catalases (CAT) that dismutate specific ROS to less reactive or harmless chemical species. Due...

Coordinated UpRegulation of the Antioxidant Network

Much of the earlier literature focused on the response of multiple components of antioxidant defenses in plants suffering traumatic oxidative stress and bear out this notion of coordinated regulation of an antioxidant network (Foyer and Mullineaux, 1994 Noctor and Foyer, 1998 Asada, 1999). The activities of enzymes, levels of various antioxidants, and control at the levels of translation, RNA turnover, and de novo transcription have been described for the regulation of antiox-idant defenses under these severe stresses. The above reviews provide many individual examples of the types of control on the expression of genes of the antioxidant network. Fig. 2. An example of an antioxidant network spanning subcellular compartments. The regeneration of ascorbate (Asc) at the plasma membrane (PM after Horemans et al., 2000). Asc is either directly re-reduced by a -type cytochrome-mediated electron transfer (cyt b) or by the action of a cytoplasmic NADH-MDHA oxidoreductase (R). Alternatively,...

Antioxidant Systems

The halophytic plants display a cascade of events upon exposure to environmental stresses leading to metabolic disturbance. The cascade of events include physiological water-deficit abscisic acid-regulated stomatal closure in leaves, limited CO2 availability, over-reduction of electron transport chain in the chloroplast and mitochondria and finally generation of reactive oxygen species (ROS). These ROS are highly toxic and in the absence of protective mechanism in the plant can cause oxidative damage to proteins, DNA, and lipids (Mittler 2002 Miller et al. 2010). Additionally, this may also lead to alteration in the redox state resulting in further damage to the cell (Mittler et al. 2004). To regulate the ROS levels, plant cells are evolved with complex enzymatic and nonenzymatic antioxidant defense mechanisms, which together help to control the cellular redox state under changing environmental conditions. A correlation between enzymatic and nonenzymatic antioxidant capacitance and...

Antioxidant Defense

Plants possess several antioxidative defense systems to scavenge ROS in order to protect themselves from oxidant stress, including that caused by heavy metals (Benavides et al. 2005). These include both non-enzymatic antioxidants such as GSH and ascorbate (ASA), and enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), and guaiacol peroxidase (POD). The unique structural properties in GSH such as broader redox potential, abundance, and wide distribution render it as a good non-enzymatic scavenger of ROS in plants. Treatment of the hyperaccu-mulating ecotype of S. alfredii with the GSH synthesis inhibitor L-buthionine-sulfoximine (BSO) resulted in a significant damage in leaves with a concomitant Polyamines such as putrescine (Put), spermidine (Spd), and spermine (Spm) are polybasic aliphatic amines that play a major role in various physiological and developmental processes in plants. Polyamines also have an...

Antioxidants

The role of reactive oxygen species (ROS) in male fertility has come under increasing speculation with regard to their physiologic and pathologic effects. Elevated levels of ROS are known to compromise sperm function and viability (damage of spermatic nuclear DNA). This oxidative stress is derived from excessive production of ROS and or impaired antioxidant defense mechanisms in the semen.21 The use of antioxidant nutrients, such as selenium, glutathione, vitamin E, and vitamin C, has produced benefits in relation to sperm health. Glutathione is an important part of sperm antioxidant defense and has been repeatedly shown to have a positive effect on sperm motility when subjects took supplements with this antioxidant.24-26 In one interesting study, 600 mg of glutathione was administered intramuscularly to subjects, every other day for two months. Compared to subjects in a placebo group, men in the treatment group experienced a statistically significant effect on sperm motility,...

Free Radicals

Free radicals are believed to play a role in the pathogenesis of MS. Persons with MS have elevated concentrations of markers of nitric oxide (NO) production, including nitrate and nitrite, in their cerebrospinal fluid (CSF), blood, and urine. Research suggests that NO has a role in the axonal degeneration and impairment of axonal conduction, disruption of the blood-brain

Generation of O Ho Oh and other ROS in Plant Cells

Most ROS in plant cells are formed via dismutation of superoxide, which arises as a result of single electron transfer to molecular oxygen in electron transfer chains principally during the Mehler reactions in chloroplast (Asada 1999, Asada 2006). In case of photosynthetic electron transport O2 uptake associated with photo-reduction of O2 to superoxide (Fig. 2) is called Mehler reaction, in honor of the discoverer (Mehler 1951). Although photo-reduction of oxygen is an important alternative sink for the consumption of excess energy, but it is always associated with the generation of toxic ROS (Varnova et al. 2002). If the accumulation of ROS exceeds the capacity of enzymic and non-enzymic antioxidant systems to remove them, photodynamic damage to photosynthetic apparatus ensues, which leads to cell destruction. The dearth of NADP+ in PS I due to redox imbalance causes spilling of electron on to molecular oxygen triggering the generation of O2- The regulated activation of Calvin cycle...

Possible Roles of Radicals in Plants

Infection caused by pathogens that is recognized by a gene-for-gene interaction (Keen 1990) as incompatible results in the activation of the salicylic acid-dependent pathway, initiation of the nitric oxide (NO) signaling cascade and SA-induced massive production of free radicals (Vlot et al. 2008). The roles that these radicals play in the limitation of pathogen spread include, direct killing of pathogens, killing infected cells or and cell wall strengthening in cells surrounding infected cells (Chamnongpol et al. 1998). It is a curious fact that apparently the first wave of radicals produced occurs regardless of whether a pathogen is recognized (an incompatible interaction) or not (a compatible interaction) (Grant et al. 2000). It can be suggested that the initial boost of free radicals is involved in a certain type of systemic signaling, perhaps a warning which plants produce to prepare non-treated tissue for incoming pathogens. The second larger burst of...

The Role of Radicals in DNA Damage and Signaling in Plants

Plants have certain spontaneous levels of radicals in cells and certain spontaneous levels of HRF. It can be suggested that to increase the recombination rate, an extra level of radicals is required. It seems that inhibition of catalases was not sufficient to raise the concentration of free radicals to damaging levels. As to the mode of action of catalase, it has a low affinity for H2O2 and removes only excess levels of hydrogen peroxide (Willekens et al. 1997). For a cell, the function of catalase is 'duplicated' by enzymes of the ascorbate-glutathione cycle with high affinity for H2O2 (Willekens et al. 1997). It has been hypothesized that when plants are exposed to AT, catalases are inhibited, and H2O2 endogenously produced is scavenged by ascorbate peroxidase (APX). This idea was indeed supported in the experiment in which RB and AT were applied simultaneously. Plants that were treated with both agents had significantly higher recombination frequencies than those that were treated...

Cellular Localization of Ascgsh Cycle

The sub-cellular localization of the components of ASC-GSH cycle in plant cells has been widely discussed. The presence of ASC and GSH pools has been demonstrated in almost all cellular compartments (Fig. 2) (Noctor and Foyer 1998). Moreover, the ASC pool in each compartment seems to be specifically regulated. In cytosol and chloroplasts, ASC concentration is in millimolar range and the reduced form is predominant, at least in physiological conditions. In the apoplast and within the vacuole, ASC content is in micromolar range and its redox state, expressed as ratio between ASC and ASC+DHA, is shifted towards DHA (Foyer and Lelandais 1996, de Pinto et al. 1999, De Gara and Tommasi 1999, Hernandez et al. 2001). ASC seems to be the only antioxidant which has buffering capability in the apoplast, where it is involved in growth and defense processes (de Pinto and De Gara 2004).

Heat Shock and the Defense Responses Activated in the Redox Sensitive Pathways

These last results underline that the route for understanding redox signaling still requires a deeper study in order to better understand the role played by each cellular compartment in the interplay between ROS and antioxidant networks. Asada, K. The role of ascorbate peroxidase and monodehydroascorbate reductase in H2O2 scavenging in plants. pp. 715-735. In J.G. Scandalios ed. 1987. Oxidative Stress and the Molecular Biology of Antioxidant Defences. Cold Spring Harbor, Cold Spring Harbor Laboratory Press, USA. Asada, K. and M. Takahashi. Production and scavenging of active oxygen in photosynthesis. pp. 227-287. In D.J. Kyle, C.B. Osmond and C.J. Arntzen eds. 1987. Photoinhibition. Elsevier, Amsterdam. Chew, O. and J. Whelan, and A.H. Millar. 2003. Molecular definition of the ascorbate-glutathione cycle in Arabidopsis mitochondria reveals dual targeting of antioxidant defences in plants. J. Biol. Chem. 278 46869-46877. Del Rio, L.A. and F.J. Corpas, L.M. Sandalio, J.M. Palma, M....

ROS Signaling Pathways Regulating Potato Tuberization

An oxidative burst results in the generation of ROS, which are known to induce an intracellular signaling pathway (Grant et al. 2000). Despite a possible role of an oxidative burst in the signaling network of the tuberization process, a direct evidence for the involvement of ROS molecules in a developmental process like tuberization is rather recent. Till date, research in this field is, however, limited to the characterization and transgenic expression of the antioxidant enzyme superoxide dismutase (SOD EC 1.15.1.1) that converts two O2' radicals into H2O2 and O2. In plant systems, there are three types of SODs-MnSOD, FeSOD and Cu ZnSOD, and they are regarded as the base components in an antioxidant protective system against ROS-induced oxidative damages (Zelko et al. 2002). Of the three different SOD isoforms, Cu ZnSOD is localized in both cytoplasm and chloroplasts. A chloroplast-localized SOD (chCu ZnSOD) associated with bulb formation in lily has been isolated and characterized,...

Environmental Stress and Production of ROS

Although it is clear that ABA can impose an oxidative stress, an enhancement capacity of oxidative stress tolerance may imply that the plant need to mobilize the whole antioxidative defense systems to resist oxidative damage in stressed plant tissues. Sgherri et al. (1994) found that during drought stress of Boea hygroscopica, antioxidants such as glutathione and ascorbate accumulated. In sunflower seedlings there is an induction of antioxidant enzyme activities and increase in GSH contents when plant reached a moderate level of water deficit stress (Bruke et al. 1985). Lipid soluble antioxidants such as a-tocopherol, p-carotene, total thiol content along with a coordinated response of glutathione reductase and ascorbate to limit the free radical depending effects of water stressed wheat leaves. But their finding clearly suggests the view that ROS formed at membrane level after exposure to moderate water stress. Bartoli et al. (1999) showed that ascorbate peroxidase, glutathione...

ROS Production during Senescence

The following hypothesis of sequences of events during senescence involving ROS has been put forward. Initially membrane lipid got degraded by lipid degrading enzymes like phospholipase D, phosphatidic acid, phosphatase etc., inducing release of free fatty acids. Peroxidation of free fatty acids (containing cis, cis 1,4 pentadiene moiety) by lipoxygenase, and nonenzymatically catalyzed by free radicals, leads to the production of ROS, promotion of burst of ethylene and acceleration of senescence .

Conclusion and Future Prospects

The present research on the role of ROS, as signal molecules, in tuber morphogenesis is too elementary to render us unable to develop an integrated view of ROS signaling pathways regulating in planta tuberization in potato. Current data show that the post-harvest development (ageing) of potato tubers is associated with an increased ROS production, however, an efficient antioxidant machinery involving the major enzymatic antioxidants, such as SOD, ascorbate peroxidase (APX) and catalase (CAT) avoids an effective build-up of oxidative damage (Delaplace et al. 2009). The production of ROS during tuber dormancy breaking vis- -vis tuber sprouting is the result of enhanced metabolic activity, such as respiration. Since similar mechanisms are thought to operate during tuber formation and tuber sprouting (Vreugdenhil 2004), the regulatory effects of ROS signal molecules on tuber induction and development cannot be ignored. Despite an unambiguous evidence for the involvement of O2 , as a...

ROSinduced Cell Death Network

Many of the genes recruited in the first steps of the signaling are involved in the generation of ROS necessary for triggering PCD (NADPH oxidases, extracellular peroxidases), whereas others are responsible for the modulation of ROS levels (catalases, APXs, and other antioxidant enzymes) (Gadjev et al. 2008). Alterations in sodium, potassium, and calcium ion fluxes are among the earliest events that follow elevation in ROS levels. The transient Ca2+ oscillations are stress-specific and can lead to various downstream effects, including PCD, through the numerous Ca2+-interacting proteins, like calmodulins and calcium-dependent protein kinases (Harper et al. 2004, Yang and Poovaiah 2003). Ca2+ influx from intra- and extracellular sources is regulated by various ion channels and antiporters. Recently, the cyclic nucleotide-gated channel 2 (CNGC2 DND1) has been identified as an essential component in nitric oxide

Abstract

Degradation of membrane lipids, resulting in free fatty acids, initiates oxidative deterioration enzymatically (by providing substrate for enzyme lipoxygenase) or nonenzymatically, causing membrane lipid peroxidation. Since lipid peroxidation (both enzymatic and nonenzymatic) is known to produce alkoxy, peroxy radicals as well as singlet oxygen, these reactions in the membrane is a major source of ROS in plant cells. The spatial compartmentalization of ROS producing enzymes in specialized domain of plant plasma membrane (membrane rafts) is also a key element in the generation of ROS. However, the steady state level of ROS and its consequence in plant cells is largely determined by antioxidant systems, comprising a variety of antioxidant molecules, quenchers and enzymes. Although plants are equipped with those molecules (antioxidants) to combat enhanced level of ROS, in other circumstances plants appear to produce ROS purposefully and exploit these molecules as signaling molecules to...

Conclusion

The results of our work suggest the existence of a fine-tuned balance in the amount of free-radicals in plant cells. Cells are able to effectively regulate this balance. Apparently, the external application of radical-producing stress changes the redox balance, transcriptome and depending on the level of changes can trigger different responses. Certainly, more extensive analysis of this phenomenon is needed in the future. It is not clear how the external oxidant concentration correlates with the actual level of radicals inside the cell. It is not known whether the plant transcriptome changes upon exposure to the levels of oxidants described above. It is also not clear whether these changes are different depending on the concentration of oxidants applied. It would be also interesting to test whether pretreatment with different types of oxidative stress-generating compounds results in the same level of protection.

Photoprotection Photoinhibition Gene Regulation and Environment

Key plant responses are photoprotection and photoinhibition. In this volume, the dual role of photoprotective responses in the preservation of leaf integrity and in redox signaling networks modulating stress acclimation, growth, and development is addressed. In addition, the still unresolved impact of photoinhibition on plant survival and productivity is discussed. Specific topics include dissipation of excess energy via thermal and other pathways, scavenging of reactive oxygen by antioxidants, proteins key to photoprotection and photoinhibition, peroxidation of lipids, as well as signaling by reactive oxygen, lipid-derived messengers, and other messengers that modulate gene expression. Approaches include biochemical, physiological, genetic, molecular, and field studies, addressing intense visible and ultraviolet light, winter conditions, nutrient deficiency, drought, and salinity. This book is directed toward advanced undergraduate students, graduate...

Is There Commonality Facilitating Desiccation Tolerance Among Organisms

Late embryogenesis abundant (LEA) proteins, sucrose and certain oligosaccha-rides accumulate coincidently with the acquisition of DT during orthodox seed development (Buitink et al., 2002), and particular antioxidant enzymes become prominent (Bailly, 2004). The expression of at least 16 different LEA genes (identified from a survey of only 425 cDNAs) (J.M. Farrant, 2005, University of Cape Town, South Africa, personal communication) has been found to occur in the leaves of the xero-tolerant resurrection plant, Xerophyta humilis (Baker) Dur. and Schinz during dehydration (Collett et al., 2004). The antioxidant 1-cys-peroxiredoxin, which had previously been considered to be seed-exclusive, was found to be abundantly expressed in tissues of the resurrection plants X. humilis and X. viscosa (Baker). Illing et al. (2005) also reported that sucrose accumulates only in the tissues of the desiccation-tolerant Eragrostis nindensis (Ficalho & Hiern), and not in related sensitive Eragrostis...

Processing and utilization

Soybean polypeptide is a hydrolyzed product of protein through special treatment. Generally, it consists of peptides of 3-6 amino acids. Soybean polypeptide has a high nutritional value, high digestibility coefficient and low antigenicity, and the results of experiments show that its digestibility coefficient is much better than that of protein or amino acids. Soybean poly-peptide can be used as a raw material for or additive to health foods. It has a therapeutic effect on high blood pressure and cardiovascular and cerebro-vascular diseases, and is safe and reliable. Soybean polypeptide also decreases the deposition of subcutaneous fat and increases fat burning and it is, therefore, a safe food for people who want to lose weight. Soybean polypeptide also has an antioxidant effect, and it has been claimed that the muscle cells of athletes recover faster when they imbibe a polypeptide-containing drink (Wang et al., 2004).

Supporting Healthy Sexual Functioning For Both Genders

Ginkgo (Ginkgo biloba) has vasodilatory effects and has been shown to help men with erectile dysfunction. In two studies,16,17 men with impotence noted meaningful benefits when they took ginkgo. Ginkgo's vasodilatory effect can help both men and women who want to achieve optimal sexual function. Like arginine, ginkgo is a natural substance that enhances circulation yet ginkgo has potent antioxidant and vascular stabilizing effects as well. Thus, this herb not only serves as a treatment in addressing symptoms, but nourishes the body at the same time. The herb accomplishes this by facilitating microvascular circulation, vasodilation, and smooth-muscle relaxation.18 Ginkgo and ginseng have been shown to relax smooth muscle and thereby increase circulation.19

Alternative Treatments And Lifestyle Changes

N-acetyl-cysteine (NAC) is an acetylated ester of the amino acid L-cysteine. NAC has a significant ability to raise glutathione levels in the body, important for its potent antioxidant activity. NAC is also used to treat lung conditions as an expectorant and mucous thinner, and to produce anti-inflammatory effects.44 Studies suggest that NAC decreases production of pro-inflammatory cytokines, such as TNF-alpha, which have been shown to be elevated in individuals with OSA.45

Oneelectron reactions

GSH reacts preferentially with free radicals, such as oxygen-, carbon- or nitrogen-centered radicals, whereas reducing (electron-donating) radicals such as pyridinyl radicals are unreactive toward thiols. In these reactions GSH donates hydrogen atoms, which is one of the most important biological function of glutathione. This hydrogen donor activity results in the production of the thiyl (GS') radical. Thiyl radicals are sufficiently stable so that they are readily formed and unreactive toward other hydrogen donors. The formation of the disulphide GSSG results from dimerisation of these radicals

Programmed Cell Death

The final phase of starchy endosperm development in cereal grains involves cell death. Indeed, cell death is an important part of the development and maintenance of many tissues and organs in plants and animals (Buckner et al. 2000 Krishnamurthy et al. 2000). PCD can be triggered in cells that have served their function, such as transmitting cells of the postpollination stigma and the antipodal and synergid cells in the postfertilization megagameto-phyte, or cells that die as part of differentiation, such as xylem tracheary elements and cells that recognize pathogens (Krishnamurthy et al. 2000). The regulation of PCD has been well studied in animal cells, but the process is not equally well understood in plants. The trigger for PCD can be from signals generated outside or inside the cell, and they lead to signaling events that result in a cascade of hydrolytic activity (Krishnamurthy et al. 2000). Some of the signals generated in animal cells include calcium fluxes, production of free...

Morphology and physiology

Desiccation tolerance is not yet fully understood in bryophytes but it does involve components present in the cells sugars, largely sucrose, and protective proteins including antioxidants and enzymes involved in protection from the generation of reactive oxygen species (ROS). A genomic approach is currently being used to catalog genes whose products play a role in responses of bryo-phytes to desiccation and rehydration, but much remains to be resolved. The sequencing of the genome of Physcomitrella patens is an important tool. Even though P. patens is not a desiccation-tolerant species, researchers now have the ability to knock out and replace its genes, which will be a powerful tool for future work.

Small Molecules Involved In Signaling And Execution Of Hr Cell Death

Superoxide anion generation in relation to HR was first reported for potato tuber slices inoculated with an avirulent race of Phytoph-thora infestans (Doke, 1983). Subsequently, the oxidative burst has been identified in numerous plant-pathogen interactions involving different kinds of pathogens. The origin of ROI generated during the oxidative burst is not unequivocally established, but candidate reactions are the action of a plasma membrane-located NADPH-depend-ent oxidase complex and cell wall peroxidases (Wojtaszek, 1997 Grant and Loake, 2000). The cytotoxicity and reactive nature of O2-requires its cellular concentration to be carefully controlled, which can be achieved by induction of antioxidant enzymes, such as glutathione S-transferase, glutathione peroxidase, or ascorbate peroxidase (Wojtaszek, 1997 Smirnoff, 2000).

Nutritional Strategies for Prevention

The fiber from wheat bran, for example, is deserving of special attention, as it may be able to decrease the risk of colon cancer via various mechanisms. One of the principal ways in which a high cereal fiber diet may be beneficial is by decreasing the amounts of secondary bile acids that are irritating to the colonic mucosa. In fact, at least one of these secondary bile acids, deoxycholic acid, increases the proliferation of colonic epithelial cells.12 Research has shown that these bile acids, including deoxycholic acid, were significantly reduced when subjects consumed 10 g per day of wheat bran, but not oat bran, as an addition to their typical Western diet.13 Also, intake of dietary carbohydrates, particularly from degradation-resistant starches and dietary fiber, are fermented in the colon and form short chain fatty acids (SCFA), primarily acetate, propionate, and butyrate. These SCFAs have been shown to decrease proliferation and migration in experimentally induced cancer cell...

Summary And Conclusions

Antioxidant and antiatherogenic properties of PJ, either directly (by measuring the size of the atherosclerotic lesions, or the extent of foam-cell formation), or indirectly (by measuring such parameters as the level of plasma lipoproteins, blood platelets, activities of various enzymes associated with oxidative stress, and gene expression). However, these studies provide little information about the phytochemical constituents responsible for the observed activities, or about the bioavailability of the suspected active agents. The instances in which specific components of PJ were tested involved in vitro experiments, and as such their contribution to an exploration of the role of specific molecules in pomegranate fruits is less significant. The tendency for this type of research (i.e., in which the in vivo effect of the whole fruit is investigated) to become dominant may have several explanations it is a relatively young field, giving it a higher chance of yielding positive results...

Better Use Of Existing Herbicides

Herbicide safeners are chemicals that reduce herbicide toxicity to crop plants via a physiological mechanism, usually by enhancing herbicide metabolism. They can be used to examine systemwide effects of an herbicide application on a target species. For example, Castro et al. t2005) treated grapevine with flumioxazin and found that thirtytthree distinct proteins had altered synthesis patterns compared with untreated plants. These proteins included a diverse range of functions including photosynthesis-related proteins and antioxidant systems, allowing an overview of the systemic effects of the herbicide application. Zhang and Reichers (2004) used a similar approach to examine the influence of the herbicide safener fluxofenim on the chloroacetamide herbicide dimethenamid in wheat. They found that the safener caused eighteen proteins to be induced, including fifteen glutathione - S - transferase (GST) subunits and three proteins with known roles in glycolysis and the Krebs cycle....

Abiotic Stresses and ROS in Crop Plants

ROS are free radicals of oxygen that are chemically active. Presence of unpaired electrons in the valence shell of these molecules renders them highly reactive, resulting in damage of cell structure and function. Plant cells continuously produce ROS even under normal condition, since they play an important role in cell signalling, but when produced in excess leads to oxidative stress. Plants maintain a steady state balance between ROS production and anti-oxidant defence mechanism under normal condition, but various abiotic

Human Use of Defensive Chemicals

The nervous system activity of some alkaloids has been exploited for recreational and religious drug use (opium, cocaine, nicotine, caffeine, and mescaline) and medicine (opium and codeine). The ability of some to block signal transmission at neuromuscular junctions makes them important in surgery as well as hunting tools (e.g., curare). Polyphenols have broad antimicrobial activity they inhibit oxidative enzymes (e.g., cyclooxygenases) that cause disease, and their antioxidant characteristics are thought to prevent aging and some cancers. Much the same has been claimed for glucosinolates (cabbage family). More than 90 percent of the medicines prescribed in the twentieth century were originally plant derived, mostly involving presumed defensive chemicals. Human medicinal use of plants is based almost entirely on the action of defensive chemicals.

Antioxidative Properties Of The Pomegranate Tree Parts

Since pomegranate tree parts may also contain polyphenols with antioxidant activ-ity,57 we have prepared ethanolic extracts of whole crude pomegranate plant parts. The polyphenol concentrations in these extracts decreased in the following order bark stem whole fruit juice leaves. In the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging capacity assay, using similar total polyphenol content (10 pmol of total polyphenols L) from each of the pomegranate tree parts, the following order of potency was observed bark whole fruit juice stem leaves. Analysis of the antioxidant activity against copper ion-induced LDL oxidation, using similar total polyphenol concentrations, revealed a dose-dependent inhibition of LDL oxidation. These results suggest that different polyphenolic flavonoids are present in the pomegranate tree parts and, hence, on using total polyphenol content, specific flavonoids exert different antioxidative potency. The pomegranate flower powder ethanolic extract...

The Latest Stage of Nodulation Nodule Senescence

Besides hormones, ROS are also important in nodule senescence. Several reports demonstrate a decrease in antioxidant enzymes and in ascorbate and glu-tathione during nodule senescence. Differences in ROS levels seem to be more variable depending on nodule type, legume species or experimental conditions. Several hypotheses have been proposed but more experimental data are needed to elucidate the role of ROS during nodule senescence (Puppo et al. 2005).

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. GR plays a key role in the response to oxidative...

Antioxidative Capacity Of Pomegranate Juice In Comparison To Other Juices

Pomegranate juice was shown to possess an antioxidant activity that was three times higher than the antioxidant activity of green tea.63 The antioxidant activity was higher in juice extracted from whole pomegranate than that of juice obtained from arils only, suggesting that the processing extracts some of the hydrolyzable tannins present in the fruit rind into the juice. We have demonstrated that pomegranate juice contains a higher concentration of total polyphenols (5 mmol L) in comparison to other fruit juices (orange, grapefruit, grape, cranberry, pear, pineapple, apple, and peach juices, which contain only 1.3 to 4 mmol L of total polyphenols, Table 2.1). A similar pattern was noted for IC50 values, obtained for the inhibition of copper ion-induced LDL oxidation. While PJ exhibited a very low IC50 (0.06 l mL), the IC50 values for the other juices were in the range of 0.11 to 7.50 l mL (Table 2.1). The most potent antioxidant activity of PJ could be related to its high...

Metabolism In Plant Cells Under Stress Reactive Oxygen Species

Molecular oxygen dioxygen) has the unusual chemical property that it has two unpaired electrons with parallel spins. The ground-state oxygen molecule is triplet and excitation by energy transfer leads to highly reactive singlet state oxygen (singlet oxygen). The particular chemistry of oxygen also means that an univalent reduction (by accepting one single electron) is probable. This reaction yields oxygen free radicals. Free radicals are molecules with one unpaired electron, many of them very reactive. In the redox interconversion chain from 02 to H20 which requires a total of 4 electrons per 02 molecule several intermediates (ROS ) exist. All of them are less stable than 02 or water. Reactive oxygen species include the superoxide anion free radical (02 *), the hydroxyl free radical (OH*), hydrogen peroxide (H202) or the singlet oxygen. Oxidative attack initiates lipid peroxidation, protein oxidation, DNA damages, and pigment bleaching (Elstner and OBwald 1994). of peroxidases....

Metabolic Engineering

To cope up with different abiotic stresses plants alter their metabolic pathways to adjust to changed environments (Rathinasabapathi, 2000). The metabolic pathways such as proline, glycinebetaine, polyols, antioxidant components become more active to keep the plant survive under stress conditions. However, the initiation and efficiency

Health aspects of carotenoids

In human nutrition, carotenoids play an important role as a source of provitamin A. In the gastrointestinal tract 3-carotene gets converted to vitamin A, which plays an important role in the regulation of vision, growth and reproduction (Ong and Choo, 1997). More recently, however, the protective effects of carotenoids against serious disorders such as cancer (Peto et al., 1981 Shekelle et al., 1981), heart disease, squamous cell carcinoma of the lung, oral tumours and degenerative eye disease have been recognized, and have stimulated intensive research into the role of carotenoids as antioxidants and as regulators of the immune response system. The antioxidant property of 3-carotene by its effective radical trapping was studied by Burton and Ingold (1984). Kunert and Tappel (1983) reported the efficient reduction of lipid peroxidation by prior treatment with 3-carotene in guinea pigs.

Extraction and downstream processing of pungency principles and pigments of Capsicum

Provitamin-A carotenoids of Capsicum, namely 3-carotene and 3-cryptoxanthin, are reduced during the processing of paprika. Esterified carotenoids, which are found as ketocarotenoids, cap-santhin and capsorubin, are more stable than zeaxanthin (free, monoesterified and diesterified forms), 3-cyrptoxanthin (free and mono-esterified form) and 3-carotene (free form) (Howard, 2001). Loss of provitamin-A activity of 67 and 81 has been reported for paprika varieties Agridulce and Bola, respectively. (Minguez-Mosquera and Horneo-Mindez, 1994). The natural antioxidants present in the fruit prevent the degradation of colour (Kanner et al., 1979). Tocoferol acts as an oxidation barrier, while ascorbic acid is useful for tocoferol regeneration and carotenoids prevent lipid oxidation (Esterbauer, 1991). Though there are reports of a decrease of capsaicinoid upon food processing, the pungency factor is generally not affected under the conditions of oleo-resin preparation. However, prolonged storage...

Plant Mechanisms to Cope with Cadmium

Enters first by the roots through the cortical tissue. Roots accumulate Cd during its exposure and part of the metal is then translocated to leaves (Ogawa et al. 2009). Cd can be loaded rapidly into the xylem by transport to the above-ground tissues. Once Cd has entered into the cytosol, it can bind to phytochelatins or their precursor glutathione, generating conjugates that can be transported into the vacuoles, preventing the free circulation of Cd ions in the cytosol (Cobbett 2000 Verbruggen et al. 2009). Cd can also be complexated by metallothioneins and nicotianamine (Cobbett and Goldsbrough 2002 Sharma and Dietz 2006). Proline, histidine and polyamines are also involved in the defence against metal stress because they may be involved in osmoregulation and metal chelation, or they can act as antioxidants (Sharma and Dietz 2006). Referring to compartmen-talisation of Cd, it has been shown that some of the genes regulated by Cd are involved in its own transport, like AtPcrl (Song et...

Iron And Oxygen Toxicity

Bacteroids is required to provide the 15-18 ATP for each N2 molecule fixed however, oxygen toxicity is an additional concern and bacterial systems usually have an elaborate system involving oxygen stress response. Thus, there is the paradox in the nodule of having sufficient O2 but not having an excess which would be both inhibitory for gene expression or enzyme structure and toxicity attributed to the formation of free radicals. A consequence of Fe3+ presence is the interaction with molecular oxygen to produce toxic free radicals. The catecholate siderophores of Azotobacter vinelandii are important in management of oxidative stress because protochelin and azotochelin, but not aminochelin, were able to prevent the generation of the hydroxyl free radical by a series of reactions involving free Fe3+ (Cornish and Page, 1998). Reactions leading to hydro xyl radical formation are as follows The low binding affinity of aminochelin for Fe3+ is reflected by the ligand Fe3+ ratio for...

The end product of nitrate assimilation is a whole spectrum of amino acids

Proline protects a plant against dehydration, because, in contrast to inorganic salts, it has no inhibitory effect on enzymes even at very high concentrations. Therefore proline is classified as a compatible solute. Other compatible solutes, formed in certain plants in response to water stress, are sugar alcohols such as mannitol (Fig. 10.13), and betains, consisting of amino acids, such as proline, glycine, and alanine, of which the amino groups are methylated. The latter are termed proline, glycine, and alanine betains. The accumulation of such compatible solutes, especially in the cytosol, chloroplasts, and mitochondria, minimizes the damaging effects of water shortage or high salt content of the soil. These compounds also participate as antioxidants in the elimination of reactive oxygen species (ROS) (section 3.9). Water shortage and high salt content of the soil causes an inhibition of CO2 assimilation, resulting in an overreduction of photosynthetic electron transport carriers,...

Conclusions and Future Research Directions

Peroxidation and the presence of detectable amounts of H2O2. However, the combined action of energy dissipation processes, antioxidants, and antioxidant enzymatic systems in water stressed, nutrient-limited, and salinity-affected plants seems to maintain a large part of PS II undamaged, and in most cases there is no evidence for major sustained photodamage under such environmental conditions. In general, the concentrations of most oxidative defense components tend to increase with the stress when they are expressed on a basis that considers the capacity to produce reactive oxygen species (i.e. on a chlorophyll basis). In any case, oxidative stress-related processes, which are traditionally regarded as damage, could also be re-interpreted as part of the redox-regulated signal transduction pathways (Demmig-Adams and Adams, 2003). Future research should be focused to investigate these systems in plants under limited nutrient or water availability.

Conclusions and Future Prospects

The carotenoid biosynthetic pathway is now well understood. The major challenge is to provide insight into the regulatory aspects of carotenoid biosynthesis during nuclear transcription, protein translocation, plastid biogenesis and plant development. Understanding needs to be improved of how phytohormones, abiotic stress and metabolic feedback affect carotenoid composition and regulation. As knowledge of the regulatory processes increases, researchers will be able to make informed decisions about the effects of manipulating the pathway. This will allow the development of the next generation of crops which enhance and build upon the benefits of 'Golden Rice'. The result could entail significant health benefits for society by providing essential antioxidant micronutrients and vitamin A derivatives. As the health benefits from these crops can be obtained by changing the composition of foods already eaten without altering the eating habits of the consumer, they will have a much greater...

ROS Metabolism in Response to Cadmium 51 ROS Production Under Cd Stress

Reactive oxygen species (ROS) such as O2 OH or H2O2 are produced as a result of normal aerobic metabolism (Gutteridge and Halliwell 2000). An excess of ROS, however, is dangerous for the plant, mainly due to the reaction with lipids, proteins and nucleic acids giving rise to lipid peroxidation, membrane leakage, enzyme inactivation and DNA break or mutations, which can induce severe damage to the cell (Halliwell and Gutteridge 1999). Although Cd2+ is not able to directly generate ROS by a Fenton reaction, it might inhibit antioxidant enzymes, impair the respiratory chain, or displace copper and iron ions in metalloproteins, which eventually trigger a Fenton reaction (Valko et al. 2005). It has been reported that Cd produces concentration-dependent imbalances in the antioxidant defence of plants and induces oxidative stress (Romero-Puertas et al. 1999 Dixit et al. 2001 Sandalio et al. 2001). Additionally, ROS production at subcellular levels was demonstrated in plants grown under Cd...

A short summary of responses of the glutathione system to natural stress

In general, many studies revealed increases in glutathione reductase activities and or the total glutathione concentrations upon the impact of stresses. Such a response is coincident with a re-enforcement of the antioxi-dative defence systems and generally interpreted correspondingly. With more severe stress, a degradation of total GSH concentration was reported which suggested a weakening of the defence system as a symptom of initial cell disruption. However, the responses of the GSH GSSG redox state are more divergent. Oxidation of the GSH pool was regarded as a symptom of initial collapse of the antioxidant system as may be true in severe cases, but this redox ratio may also play an important role in detecting the stress level and signalling further responses (May et al. 1998). Small and transient changes in the GSH GSSG ratio preceding other responses may be possibly be interpreted in this way. Hence, the regulation aspects of the glutathione metabolism and the antioxidant system...

Conclusions and Future Perspective

AM colonization has been shown to increase plant tolerance to drought and pollution, and often reduces the typical responses of plants to stress, such as the production of antioxidant molecules or enzymes. Soil modifications induced by AM fungi have also been observed to play a role in protecting plants. However, despite the large number of studies on this topic, the underlying mechanisms of AM protection are not jet fully understood, and contradictory results have sometimes been reported. One reason for this, apart from the heterogeneity of the experimental procedures followed by different authors, may be connected to the different morphological and functional strategies of plants to decrease stress exposure or tolerate stress, and to the different efficiency of the associated AM fungi.

NO Function and Protection Under Cd Stress

Nitric oxide is an intracellular and intercellular messenger with a broad spectrum of regulatory functions in many physiological processes and responses to biotic and abiotic stresses (del Rio et al. 2006 Delledonne 2005 Wilson et al. 2008). It has also been reported that NO can act as pro-oxidant and antioxidant in plants. Actually, it can scavenge directly some ROS like the superoxide anion or indirectly changing both enzymatic or non-enzymatic antioxidant systems (Kopyra and Gwozdz 2003). It has been described that NO increases SOD activity in Lupinus luteus (Kopyra and Gwozdz 2003), delays the loss of SOD activity in barley aleurone cells (Beligni et al. 2002) or prevents Cd-induced increase of SOD from Helianthus annus (Laspina et al. 2005). Additionally, NO can restore catalase (CAT) activity, which was reduced in Cd-treated sunflowers plants (Laspina et al. 2005), also delays the loss of CAT activity in barley aleurone cells (Beligni et al. 2002) and negatively affects the CAT...

Organelles Involvement in Cd Stress

Cd (Romero-Puertas et al. 2004 Rodriguez-Serrano et al. 2009a). Cadmium treatment also produced a proliferation of peroxisomes (Romero-Puertas et al. 1999) probably due to an induction of peroxisome biogenesis genes like it was observed in both plant and animal cells as a result of the induction of H2O2 production (Lopez-Huertas et al. 2000). Cd also causes an increase in peroxisome movement rate which is independent on changes in the actin cytoskeleton and dependent of calcium and peroxisomal ROS production (Rodriguez-Serrano et al. 2009b). Peroxisomes possess a battery of antioxidants that could play an important role in controlling ROS production under Cd stress. Thus, CAT can protect Arabidopsis protoplast against Cd-induced cell death (Bi et al. 2009).

Complexed Story Iron Pools In Plant Cells

After uptake, excess iron has to be complexed or sequestered within the cell to avoid toxicity due to Fe(II)-mediated generation of free radicals via Fenton chemistry. In both Strategy I and Strategy II plants, intracellular delivery of iron and trafficking within the plant is dependent on nicotianamine (NA), which is believed to protect the cell from oxidative damage by forming stable complexes with Fe(II) and supporting its cellular distribution (von Wiren et al., 1999). NA is a polyamine formed by the the trimerization of three molecules S-adenosylmethionine to one molecule of NA via nicotianamine synthase (NAS) (Herbik et al., 1999 Higuchi et al., 1999), found in all multicellular plants investigated to date (Noma and

Chun Hu David D Kitts and Jerzy Zawistowski

In addition to posing a health risk through potential peroxidation reactions that affect cell viability, some ROS such as superoxide radical and hydrogen peroxide are also involved in important reactions that ensure optimal cellular function (e.g., phagocytosis and cell signaling). Under normal conditions, the body has a mechanism for balancing intracellular and or extracellular events, which ultimately contribute to the generation of ROS, termed oxidative stress. This condition will involve both optimal activity of various endogenous tissue antioxidant enzyme systems (e.g., superoxide dismutase, glutathione peroxidase, catalase) (Yuan et al., 1996) and the presence of nonenzymatic antioxidants that reside in close proximity to the cellular site where oxidation reactions occur (e.g.,

ROS signaling and its modulation by the ROS gene network

While Ca2+ signaling is predominantly controlled in plants by storage and release, ROS signaling is thought to be controlled by production and scavenging (Fig. 7.1 Mittler et al., 2004 Bailey-Serres and Mittler, 2006). ROS production is mediated by different cellular pathways, including respiration and photosynthesis, as well as by different proteins and enzymes encoded by the ROS gene network (e.g., NADPH oxidases, amine oxidases, and xanthine oxidase Table 7.1). In contrast, ROS scavenging is mediated by different ROS-scavenging enzymes and antioxidants that include ascorbate peroxidases, catalases, and superoxide dismutases (Table 7.1 see also a partial list of the ROS gene network of Arabidopsis in Table 7.2). These two opposing forces, i.e., ROS scavenging and ROS production, control the level of ROS in cells.

Abdul Wahid Muhammad Farooq Iqbal Hussain Rizwan Rasheed and Saddia Galani

On the eve of global climate change, temperature increase, is the most evident phenomenon. This temperature increase is posing severe threat for sustainable crop production in many countries across the globe in the form of heat stress. Plants respond in many ways to the prevailing high temperature environment, and several inter- and intraspecific differences are reported. Heat stress produces quite tangible changes at cell, tissue, and organ levels. Photosynthetic acclimation to heat stress, synthesis and accumulation of primary and secondary metabolites, induction of stress proteins are among the major adaptive responses to heat stress. The important genes expressed in response to heat stress include heat shock protein (hsp) genes, dehydrins (dhn), senescence-associated (sag) genes, stay-green (sgr) genes. As mechanisms of heat stress tolerance, plants display the maintenance of membrane stability, scavenging of ROS, production of enzymatic and nonenzymatic antioxidants and...

Metal Tolerance of ECM Associations 1131 Metal Toxicity

Mechanisms of metal toxicity comprise the elicitation of oxidative stress (even in non-redox-active metals such as Cd), depletion of antioxidant pools, competitive inhibition of the uptake of essential elements, denaturation of proteins, interference with functional groups of proteins by displacement of essential cationic cofactors, precipitation of P inducing P deficiency and membrane disruption. Cytoplasmatic

Targets of UVB radiation

Pyrimidine dimers, which has been found also in animal tissues (Yasuhira, Mitani & Shima, 1992). However, most organisms possess the enzyme photolyase which removes and replaces the thymine dimers this enzyme is induced by UV-A and blue light (Yamamoto et al., 1983 Hirosawa & Miyachi, 1983). Other UV-B effects do not depend on DNA damage, as indicated by the short response time and the lack of photoreactivation (Hader et al., 1986). In these cases, photodynamic reactions can be the mechanism by which UV-B affects the cells (Ito, 1983). When a molecule absorbs a high-energy photon, the excess excitation energy can lead to the formation of singlet oxygen or free radicals. Both types of photodynamic response result in aggressive molecular species which destroy membranes and other cellular components. Photodynamic reactions have been found to play a role in some UV-B-induced types of damage, for example, in the ciliate Stentor coeruleus (Hader & Hader, 1991). In other systems the role of...

Avoiding High Light Absorption

Photoprotective mechanisms in plants. To decrease light energy absorption in an excess light condition, chloroplasts can move away from the light (chloroplast avoidance), and antenna size can be reduced (antenna size reduction). To get rid of excess absorbed light energy, feedback de-excitation can dissipate excess energy as heat. In addition, efficient electron transport in both linear and cyclic electron transport pathways can relieve excitation pressure generated by high light. However, reactive oxygen species (ROS) are still generated, and ROS can be detoxified by antioxidant systems including carotenoids, ascorbate, and tocopherols. Inevitable damage to photosystems still occurs, and efficient regeneration can be a photoprotective mechanism. Fig. 1. Photoprotective mechanisms in plants. To decrease light energy absorption in an excess light condition, chloroplasts can move away from the light (chloroplast avoidance), and antenna size can be reduced (antenna size...

Early HaustoriumDevelopment

Genes upregulated in Triphysaria roots soon after DMBQ exposure included two NAD(P)H-dependent quinone oxidoreductases, TvQR1 and TvQR2 (Matvienko et al. 2001a, b) . In Triphysaria there is rapid transcriptional induction of both TvQR1 and TvQR2 as a primary response to DMBQ treatment. TvQR1 exhibits homology to a family of zeta-crystallins and catalyzes a one-electron reduction of quinone to semiquinone, providing a free radical consistent with the redox signaling hypothesis (Fillapova, Petite, Yoder, unpublished). TvQR2 is related to a class of detoxifying enzymes, such as human liver DT-diaphorase, and catalyzes a two-electron reduction of quinones (Wrobel et al. 2002) . We hypothesize that TvQR1 and TvQR2 act antagonistically in that TvQR1 generates free radicals and TvQR2 detoxifies them. We propose that if the activity of TvQR1 is greater than TvQR2, haustorium development proceeds if the activity of TvQR2 is greater, no haustoria form. Haustorium development in this model is...

The Cellular Thiol Disulfide Redox State as a Regulator of a Cells Response to Oxidative Stress and Drought

A correlation between water deficit and an altered thiol disulfide redox state of the protein and nonprotein thiols has been demonstrated for wheat leaves (Zagdanska and Wisniewski 1996). These leaves reached a drought-acclimated state by increasing glutathione content and glutathione reductase activity. By analyzing stomatal closure activity in GSH-deficient mutants, the involvement of thiol disulfide changes downstream of ROS production in the ABA-signaling cascade was demonstrated (Jahan et al. 2008). Redox proteomics also revealed the link between drought and oxidative stress (Hajheidari et al. 2007). Thioredoxins were shown to be responsible for stress protection in cells of all organisms, where the redox state of transcription factors is linked to apoptosis (Tanaka et al. 2000). In potato plants subjected to water deficit, a new stromal protein of 32 kDa (chloroplastic drought-induced stress protein CDSP32) was identified that carried a thioredoxin active-site motif and was...

Involvement of ROS in Dehydration Signal Transduction 1151 Interactions of ROS and ABA

Drought and desiccation cause enhanced ROS production, in particular in high light. Plants can cope with this situation, if sufficient antioxidant systems are present or are induced during an adaptation phase (Jiang and Zhang 2002b Khanna-Chopra and Selote 2007). Induction of ROS-scavenging enzymes upon osmotic stress has been demonstrated (Morabito and Guerrier 2000 Munne-Bosch and Peiiuelas 2004). The content of antioxidants is particularly important during rewatering after drought (Baroli et al. 1999). If ROS increases above a certain threshold, it can serve as a signal to induce or enhance acclimation to water stress. The level at which ROS becomes toxic, causing damage and finally cell death, exceeds that of ROS acting as signal. The role of ROS in signal transduction upon stress is highly interlinked with ROS scavenging, because nondeleterious levels are required for signal transduction from chloroplasts or mitochondria to the nucleus for the induction of antioxidant enzymes...

Conclusions and perspectives

Gould, K.S., McKelvie, J. and Markham, K.R. (2002a) Do anthocyanins function as antioxidants in leaves Imaging of H2O2 in red and green leaves after mechanical injury. Plant Cell Environ 25, 1261-1269. Philpott, M., Gould, K.S., Lim, C. and Ferguson, L.R. (2004) In situ and in vitro antioxidant activity of sweetpotato anthocyanins. JAgric Food Chem 52, 1511-1513.

Signaling in Chloroplast Movements

Obviously, signaling pathways other than those generated by light must have an impact on chloroplast redistribution. Cross-talk between environmental stress signals and the light signals controlling chloroplast movements is unquestionably of key importance. In the last decade, this aspect of cell signaling has not aroused much interest. Only one study was focused on redox signaling which may be indicative of both abiotic and biotic stress (Wen et al. 2008). Exogenous H2O2 at a concentration of 10 4 M was shown to enhance the avoidance response of A. thaliana chloroplasts. On the other hand, strong blue-light-induced H2O2 generation at the plasma membrane and the chloroplast. The light-induced H2O2 generation and the chloroplast avoidance response were largely decreased by the exogenous addition of the H2O2-specific scavenger catalase and other antioxidants (ascorbic acid and mannitol). Other compounds shown to reduce H2O2 production are DCMU and diphenyleneiodonium (DPI), an NADPH...

Flavonoids And Cardiovascular Diseases

Flavonoids compose the largest and the most studied group of plant phenolics. Over 4000 different flavonoids have been identified to date. Flavonoids are grouped into anthocyanins and anthoxanthins. Anthocyanins are glycosides of anthocyanidin, and they are the most important group of water-soluble plant pigments, responsible for the red, blue, and purple colors of flowers and fruits. Anthoxanthins are colorless or colored white-to-yellow, and include flavonols, flavanols, flavones, flavans, and isoflavones. Flavonoids are powerful antioxidants, and their activity is related to their chemical structure.118,119 Plant flavonoids can act as potent inhibitors of LDL oxidation,120,121 or of macrophage oxidation.122 Dietary consumption of flavonoids was shown to be inversely related to morbidity and mortality from coronary heart disease.123 Moreover, an inverse association between flavonoid intake and subsequent occurrence of ischemic heart disease, or cerebrovascular disease, was...

Oxidative Stress and Cell Defenses

Plants have developed a variety of strategies to prevent excessive accumulation of nonessential metals within cells and or transform these metals into less toxic forms (Cobbett 2000). Some plants produce metabolites that bind to heavy metals in the cytosol, such as glutathione (GSH), polypeptides and proteins (e.g., metallothioneins and phytochelatins) and proline (Hall 2002). However, when these defense mechanisms are not sufficient, ROS overproduction occurs, which causes oxidative stress and activates other mechanisms (Patra et al. 2004). The defense system includes enzymatic and nonenzymatic antioxidants. Representatives of the enzymatic antioxidant defense system include superoxide dismutase, ascor-bate peroxidase, and catalase for ROS removal from cells (Halliwell and Gutteridge 1989). The main nonenzymatic water-soluble defenses include ascorbic acid (AA), thiols (predominantly glutathione), a-tocopherol, carotenoids, flavonoids, and polyamines, which have also been shown to...

Compatible Metabolites That Can Prevent Detrimental Changes

Mitigate oxidative damage caused by free radicals produced in response to salt stress (Slama et al., 2008 Smirnoff and Cumbes, 1989). In many halo-phytes, organic osmolytes such as Pro or GB accumulate at suitably high concentrations to create osmotic potentials even below 0.1 MPa. However, the concentrations of compatible solutes that accumulate are not so high in glycophytes to generate osmotic pressure (Turkan and Demiral, 2009). This difference between halophytes and glycophytes can be used as an early indicator for salt resistance. Therefore, in the next chapters, the most important compatible solutes are described in detail. The contribution of Glu and Orn pathways to stress-induced Pro synthesis differs between species and it has been shown that stress-tolerant plants are able to accumulate Pro in higher concentrations than stress-sensitive plants. Slama et al. (2008) showed a positive correlation between Pro accumulation and tolerance to salt, drought and the combined effects...

Ethylene Perception and Signal Transduction

Pigments are essential for the attractiveness of fruits, accumulating most often in the skin during the ripening process, although many climacteric fruits accumulate pigments also in their pulp tissue. The most important pigments of fruit are carotenoids and anthocyanins. Beside their role in pigmentation, they are important for human health as a source of vitamin A and antioxidant compounds. Carotenoids comprise carotenes, such as lycopene and p-carotene, and xanthophylls, such as lutein. They are derived from terpenoids, and are synthesized in fruit at a high rate during the transition from chloroplast to chromoplast. Many genes involved in the biosynthesis of carotenoids have been cloned (Cunningham and Gantt 1998 Hirschberg 2001), and extensive information is available on the regulation of carotenoid formation during fruit ripening (Bramley 2002). Anthocyanins belong to the flavonoid subclass of phenolic compounds. The flavonoid biosynthetic pathway has been elucidated in plants,...

Signals Mediated by Reactive Oxygen Species and Stress Related Processes

Hydrogen peroxide (H2O2) is the principle ROS in plants. It is mainly generated at PSI under conditions when excitation exceeds energy usage by the dark reaction, e.g. under high light or in low temperature. Such conditions lead to over-reduction of the electron transport chain and to electron transfer from ferredoxin to oxygen generating superoxide (Fig. 4). This is detoxified by the superoxide dismutase (SOD) resulting in accumulation of hydrogen peroxide which is reduced to water by antioxidant enzymes such as APX. In this reaction ascorbate is used as electron donor and replenished by reduction via glutathione (Pfannschmidt 2003). Cytosolic APX enzymes are induced by oxidative conditions and therefore represent good markers for cellular stress (Shigeoka et al. 2002). In Arabidopsis high-light induction of nuclear genes apx1 and apx2 could be correlated to the action of H2O2 as a signalling molecule (Karpinski et al. 1997, 1999. Foyer and Noctor 1999) . Interestingly apx2 was also...

The Effect Of Pomegranate Juice On Hypertension

Some antioxidants such as vitamin C, vitamin E, P-carotene and coenzyme Q were recently shown to possess hypotensive properties.149-152 As PJ possesses very potent antioxidative properties, we questioned the effect of PJ on blood pressure and on serum ACE activity. PJ consumption by CAS patients significantly (p 0.05) reduced their systolic blood pressure after 1 year by 18 (from 174 22 to 143 17 mmHg)148 (Figure 4.2A). In contrast, PJ consumption had no significant effect on the patient's diastolic blood pressure (81 3 before treatment vs. 81 2 mmHg after one year of PJ consumption). Seven hypertensive males and three females with mean blood pressure levels of 155 7 83 7 mmHg were also studied.153 The patients were administered PJ (50 mL concentrate containing 1.5 mmol of total polyphenols per day) for a period of 2 weeks. PJ consumption resulted in a small (5 ) but significant (p 0.05) reduction in the systolic blood pressure (Figure 4.2B). In seven out of ten hypertensive patients...

Essential Fatty Acids

Antioxidants ROS appear to play a role in the pathology of MS. Epigallocatechin-3-gallate (EGCG), a constituent of Camellia sinensis (green tea) known for its antioxidant activity, reduced the clinical severity of experimental autoimmune encephalomyelitis (EAE) in mice when given at or after the onset of EAE in the animals, by limiting brain inflammation and reducing neuronal damage. EAE is the animal model used to study MS as this condition can be induced in laboratory animals. EAE is a demyelinating disease in which the myelin is damaged and exhibits similar clinical progression. EGCG also directly inhibited the formation of neurotoxic ROS in neurons.38 Curcumin, a constituent of Curcuma longa (turmeric) with potent antioxidant activity, is also known for its anti-inflammatory activity. Supplementation with curcumin in animal models of MS decreased the duration and severity of the disease by decreasing secretion of the pro-inflammatory cytokine IL-12 from monocytes and microglial...

Anatomy and pathophysiology of the burn wound

1 Zone of coagulation This is the central zone of tissue necrosis, also referred to as the zone of necrosis. Some of the prominent features include but are not limited to denatured proteins, coagulated blood vessels, increase in intracellular sodium as a result of falling sodium-potassium pump, a significant increase in free radicals with subsequent damage to the cell membrane, and finally protein denaturation. 2 Zone of stasis This zone surrounds the central area of the necrosis zone of coagulation. In this zone, there is impaired circulation. It is also known as the zone of ischemia. Tissue in this area can heal without any complication, or the lesion can progress and lead to a greater depth of injury. This zone of ischemia is as a result of thermal injury to the red blood corpuscles rendering them inflexible and unable to enter the microvasculature. Edema occurs over time, as a result. There is an influx of inflammatory mediators including histamine, prostaglandin E (PGE),...

And Postharvest Produce

These diverse stresses activate similar cell-signaling pathways and cellular responses, such as the production of stress proteins, upregulation of antioxidants, and accumulation of compatible solutes (Wang et al. 2003). Thus, plant stress responses are regulated by multiple signaling pathways that activate gene transcription and its downstream machinery (Wang et al. 2003). The complex plant response to abiotic stress involves many genes and biochemical-molecular mechanisms. The molecular control mechanisms of abiotic stress tolerance, which may result in the use of molecular tools, is based on the expression of specific stress-related genes (Wang et al. 2004). These major tolerance mechanisms include water and ion uptake and transport, such as ion transporter and aquaporins, osmoprotectants, free-radical scavengers, the protection of membranes and proteins, such as heat-shock proteins (HSPs) and chaperones, late embryogenesis-abundant proteins, and factors involved in signaling...

Helena Sestakova and Bohumil Turek

The plants of the genus Echinacea possess a number of known bioactive properties, including antioxidant and anticarcinogenic effects. The study of parts of plants of genus Echinacea or of their components, in terms of their capacity to influence the immune mechanisms of an organism, is therefore very important for the assessment of protection against various pathogens. Immunologic studies are generally concerned with the response of an organism to foreign (extraneous) substances entering the body. The basic function of the immune system is to differentiate between foreign and one's own molecules, and to protect against extraneous proteins. An immune reaction takes the form either of a specific response mediated by T and B cells, or of a nonspecific (natural) response mediated by macrophages, natural killer cells, and polymorpho-nuclear leukocytes (PMNLs). A positive or negative effect on immunity of substances obtained from plants or of nutritional factors is therefore very important...

Flavonoids have multiple functions in plants

Many flavonoids are antioxidants in acting as radical scavengers for reactive oxygen species (ROS), thus preventing the peroxidation of lipids. As constituents of nutrients, they are assumed to be protectants against cardiovascular diseases and cancer. For this reason, nutrients containing flavonoids (e.g., green tea, soy sauce, and red wine) have been regarded as beneficial for health.

Oxidative stress and ferritin gene expression

Iron reactivity with oxygen produce free radicals (Briat, 2002). Therefore Fe storage and buffering is a key element of the defense mechanisms evolved by living organisms to cope with oxidative stress. Ferritins are playing an active role in these mechanisms because of their ability to store thousands of Fe atoms in a safe form (Harrison and Arosio, 1996). Indeed ferritin over-expression in transgenic plants has been shown to protect against paraquat promoted oxidative stress (Deak et al., 1999 Van Wuytswinkel et al., 1999 Zer et al., 1994). Furthermore, pro-oxidant treatments such as H2O2, NO or ozone applications as well as high light intensity are known to induce ferritin synthesis (Gaymard et al., 1996 Lobreaux et al., 1995 Murgia et al., 2001 Murgia et al., 2002 Tarantino et al., 2003). However, whether the regulation of ferritin expression in response to Fe excess and oxidative stress occurs through common, independent or branched pathways is still unclear.

Environmental Effects on Plastid Division

Because of their sessile nature higher plants constantly respond to environmental factors by moulding metabolic, redox and developmental processes in accordance to the environmental inputs. The response of a plant to environmental signals can range from slight acclimation, resulting for example in changes in protein phosphorylation and small antioxidants redox state, to more dramatic changes such as modifications of gene expression and ultrastructural alterations. Because plants are often challenged by different factors giving rise to additive, multiplicative or synergetic reactions, a high degree of developmental plasticity in response to environmental signals is required.

Effects of Oxidative Stress

As described above, various studies suggest that ROS and, in particular, 1O2 are the primary cause of photodamage to PS II. According to the proposed acceptor-side and low-light mechanisms, the O2 that is formed by the transfer of energy from triplet chlorophyll damages the D1 protein, and this damage triggers the enzymatic degradation of the D1 protein (Vass et al., 1992 Keren et al., 1997). The generation of 2 can be detected when PS II complexes, thylakoid membranes, and plant leaves are illuminated (Telfer et al., 1994 Hideg etal., 1994, 1998). Exposure of thylakoid membranes to O2 results in the selective and specific cleavage of the D1 protein (Okada et al., 1996). Other ROS, such as H2O2 and O2-, also induce the specific cleavage ofthe D1 protein in vitro (Miyao et al., 1995). Free-radical scavengers protect the D1 protein from degradation in Spirodela plants, suggesting that oxygen free radicals, such as OH, are involved in the light-dependent degradation of the D1 protein...

Biotechnological Potential of ECM Fungi Producing Metal Chelating Agents

However, siderophores can have other important applications related to the environment in the uptake of metals from industrial waste, low-grade ores, serpentine soils, contaminated terrestrial and aquatic environments, tailings of abandoned mines, etc. The uptake of metals can serve to remediate an environment and or recover metals for recycling. In addition, the capacity to chelate actinides (Pu, U, Np, and Th) has been demonstrated in siderophores and for this reason their application has been proposed for the remediation of radioactive waste and the reprocessing of nuclear fuel (Hernlem et al. 1999 Renshaw et al. 2002, 2003). The majority of these studies have been conducted with commercial hydroxamate siderophores like desferrioxamine B and some with siderophore-producing soil microbes (John et al. 2001 Keith-Roach et al 2005 Mullen et al 2007). Therefore, this is an area where other fungal hydroxamate siderophores, like those produced by ECM fungi, could have a...

Transcription Factors Involved in ABA Signal Transduction

Expression of ABA-response genes is stimulated by transcription factors bZIP, viviparous1 (VP1) ABI3, and AP2. The bZIP proteins are probably ubiquitously present in nucleus, being activated by phosphorylation. All SnRK2s can in the nucleus directly phosphorylate bZIP transcription factors of ABF AREB ABI5 group, which further stimulate the expression of ABA-response genes. Upregulated genes are coding for, e.g., dehydrins, antioxidant enzymes, transporters, PYR PYL RCARs, transcription factors, protein kinases, protein phosphatases, and enzymes of phospholipid signaling (Cutler et al. 2010). The bZIP transcription factors interact in dimers with the G-box of ABA-response elements (ABRE) in the promoters of ABA-response genes. The bZIP dimers may interact with 14-3-3 proteins and VP1(ABI3) transcription factor (Himmelbach et al. 2003) .

Chloroplast redox signals

At high irradiances, and other stress conditions such as exposure to low temperature, the equilibrium between production and scavenging of ROS is perturbed, resulting in a transient increase in ROS levels (Karpinski et al., 2003). The ROS generated in chloroplasts are singlet oxygen (1O2) by PSII and the superoxide anion (O -) formed at PSI due to an over-reduction of electron carriers, leading to the reduction of oxygen (the Mehler reaction). The accumulating O - can be metabolized to H2O2 (Mullineaux and Karpinski, 2002 Apel and Hirt, 2004). The damaging effects of ROS are oxidation of lipids, proteins, and enzymes necessary for the proper function of the chloroplast and the cell as a whole (Foyer and Allen, 2003). Plants have developed several strategies to protect themselves against excess ROS. Carotenoids, toco-pherols, glutathione, and ascorbate are all ROS scavengers (Niyogi, 1999). ROS-converting enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase...