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Sugar Crush Detox

This program was designed by Jane who had the same problems with sugar. Throughout her life, she was addicted to sugar and she thought she needs swift intervention before that habit develops into something else. She had an experience that helped her beat sugar addiction with the rest of the world. Her program helps you cut all the roots of majority of the health problems you usually gets. It attacks the weight loss problem at its source which is the biological craving for sugar. This product was specifically created to help people with sugar cravings beat this addiction and lead a healthy life. This program contains a couple of guides available in PDF, MP3 and video formats. The author used simple language in all the formats to ensure that everybody will be able to handle sugar addiction. If you are one of them and you want to get the full support required to quit sugar and lead a heathy life, then Sugar Crush Detox is for you. More here...

Sugar Crush Detox Summary


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Sucrose Cycling In Storage Parenchyma Cells

When arrived in the storage cells, sucrose metabolism is achieved by several different enzymes performing the same or similar reactions and which operate in parallel. The symplastic enzymes directly involved are in direction of sucrose synthesis sucrose-phosphate synthase (SPS) (in concert with sucrose-phosphate phosphatase) and sucrose synthase (SS), and in direction of sucrose breakdown soluble acid invertase (SAI), neutral invertase (NI) and sucrose synthase (SS) (Fig.3). The reaction products, glucose, fructose and UDP-glucose can be recycled to precursors of sucrose synthesis again by hexokinase, phosphoglucoisomerase (PGI) and UDP-glucose pyrophosphorylase (UDPG-PPase). All these enzymes are supposed to be cytosolic with exception of the soluble acid invertase, which is vacuolar. In addition a cell wall bound acid invertase will hydrolyse apoplastic sucrose. The presence of these enzymatic activities in parallel in storage tissue had been already found by the Australian group...

Involved In Sucrose Metabolism

Since it had been found in the 1960s that wild forms of sugarcane and high-yield commercial varieties are distinguished by different enzyme activities of sucrose metabolism (3), a correlation between sucrose storage (or sucrose concentration in the internodes) and enzyme activities was sought for. As pointed out before (Fig.3), sucrose undergoes a cycle of synthesis and breakdown. In theory, sucrose concentration can be increased by shifting up sucrose synthesis activity or by switching down the sucrose hydrolysis activity, whereby each of these metabolic reactions is catalysed by different enzymes in parallel, not considering even that each of these enzymes most likely is comprising a family of genes. Zhu et al. (20) analysed the progeny of a defined cross between Saccharum officinarum and Saccharum robustum and followed sucrose concentration and enzyme activities during internode ripening of low and high sucrose clones. The best correlation found, comprising all internodes and all...

Sucrose to Starch Conversion in Storage Organs

The pathway of starch synthesis in developing storage organs is relatively well understood (Figure 1.3). In all organs apart from cereal endosperms, sucrose entering the storage parenchyma is converted to G6P in the cytosol. In the case of the potato tuber, sucrose delivered by the phloem from source tissue can be metabolised in different ways. It can either be hydrolysed by apoplastic or cytosolic invertase, respectively, resulting in glucose and fructose, or converted into UDP-Glc and fructose by sucrose synthase (SuSy). The prevailing route of sucrose cleavage depends upon the developmental stage of the tuber. At the onset of tuberisation when cell division takes place, hydrolytic degradation of sucrose Figure 1.3 Principle pathway leading to the formation of starch in storage organs. The alternative route of ADPGlc via generation within the cytosol and subsequent uptake into the amyloplast, as it occurs in the endosperm cells of graminaceous species, is shown by dotted arrows....

Increasing yield by increasing sucrosephosphate synthase

Sucrose-phosphate synthase was selected for modification to see if the interaction between the chloroplast and the rest of the plant could be modified to increase yield. Worrel et al (1991) reported on tomatoes transformed with a gene forZea mays SPS with a Rubisco small subunit promoter (SSU-SPS plants). In most cases, these plants did not have increased yields (Galtier et al 1993, Laporte et al 1997, Signora et al 1998), though, in one case, substantially increased yields were observed (Micallef et al 1995). In all cases, area-based photosynthetic rates were the same or only marginally increased at elevated CO,, indicating that the extra SPS modified how the plant handled photosynthate rather than increased the immediate availability of photosynthate. Table 2. Sucrose-phosphate synthase (SPS) activity in control plants and plants transformed with 35S- or SSU-promoted SPS. Table 2. Sucrose-phosphate synthase (SPS) activity in control plants and plants transformed with 35S- or...

Sucrose as a Maturation Signal

Sucrose has a dual function as a transport and nutrient sugar and as a signal molecule triggering storage-associated processes (Smeekens 2000 Koch 2004). Increasing sucrose concentration in Vicia and pea cotyledons, as well as the barley endosperm at the onset of maturation, is mediated by sucrose transporter activity within newly established epidermal endospermal transfer cells (Weber et al. 1997b Tegeder et al. 1999 Weschke et al. 2000). It marks the switch from maternal to filial control of seed growth. In Vicia and barley, sucrose induces storage-associated gene expression and at the transcriptional level up-regulates enzymes like sucrose synthase and ADP-glucose pyrophosphorylase (AGP Heim et al. 1993 Weber et al. 1998b Weschke et al. 2000). In vitro sucrose feeding disrupts the meristematic state, induces cell expansion and endopolyploidization (Weber et al. 1996) and promotes cotyledonary storage activity at the transcript level (Ambrose et al. 1987 Corke et al. 1990). In...

Starch and sucrose are the main products of CO2 assimilation in many plants

In most crop plants (e.g., cereals, potato, sugar beet, and rapeseed), carbohydrates are stored in the leaves as starch and exported as sucrose to other parts of the plants such as the roots or growing seeds. CO2 assimilation in the chloroplasts yields triose phosphate, which is transported by the triose phosphate-phosphate translocator (section 1.9) in counter-exchange for phosphate into the cytosol, where it is converted to sucrose, accompanied by the release of inorganic phosphate (Fig. 9.1). It is essential that this phosphate is returned, since phosphate deficiency in the chloroplasts would cause photosynthesis to die down. Part of the triose phosphate generated by photosynthesis is converted in the chloroplasts to starch, serving primarily as a reserve for the following night period.

Sucrose synthesis takes place in the cytosol

The synthesis of sucrose, a disaccharide of glucose and fructose (Fig. 9.13), takes place in the cytosol of the mesophyll cells. As in starch synthesis, the glucose residue is activated as nucleoside diphosphate-glucose, although in this case via UDP-glucose pyrophosphorylase In contrast to the chloroplast stroma, a pyrophosphatase is not present in the cytosol of mesophyll cells. Since pyrophosphate cannot be withdrawn from the equilibrium, the UDP-glucose pyrophosphorylase reaction is reversible. Sucrose phosphate synthase (abbreviated SPS, Fig. 9.13) catalyzes the transfer of the glucose residue from UDP-glucose to fructose 6-phosphate forming sucrose 6-phosphate. Sucrose phosphate phosphatase, forming an enzyme complex together with SPS, hydrolyzes sucrose 6-phos-phate, thus withdrawing it from the sucrose phosphate synthase reaction equilibrium. Therefore, the overall reaction of sucrose synthesis is an irreversible process. In addition to sucrose phosphate synthase, plants also...

Sucrose transporters DSTs

In plants, SoSUT1 (Spinacia oleracea Sucrose Transporter 1) was the first disaccharide transporter (DST) functionally characterized in a yeast mutant deleted for invertase and expressing sucrose synthase (Riesmeier et al. 1992). DSTs genes, which belong to small multigenic families with 9 members in Arabidopsis and 4 in tomato for instance, encode for a 55 kD polypeptide (Arabidopsis Genome Initiative 2000, Delrot et al. 2001, Sauer et al. 2004, Hackel et al. 2006). Plant DSTs can be clustered into 4 groups regarding their protein sequence homologies group 1 and group 2 are exclusively composed by Group 3 transporters have been reported to localize all along the sieve element and have been proposed to sense the sucrose flux through the plasma membrane (Schulze et al. 2000). Group 4 sucrose transporters are low affinity high capacity transporters (LAHC) localized in the membranes of minor veins of source leaves (Weise et al. 2000). However, their subcellular localization is...

Endocytic Uptake of Solutes and Sucrose into Suspension Plant Cells

That a portion of the nutrients stored in the vacuole are taken up by endo-cytosis was recently established using sycamore cell cultures in conjunction with the endocytic inhibitors wortmannin and LY294002, and Lucifer Yellow as the fluid-phase endocytosis marker (Etxeberria et al. 2005a). When transferred into a sucrose-rich medium, cells accumulated sucrose rapidly for approximately 60 min. Sucrose uptake during this period proved to be wortmannin and LY294002 insensitive. After 90 min incubation, the rate of sucrose uptake increased rapidly in a linear manner for an additional 6 h. This second phase was strongly suppressed by the endocytic inhibitors wortmannin and LY294002, which would be in conformity with the existence of an endo-cytic transport of sucrose into the cells. Complete cessation of sucrose uptake by wortmannin occurred at a time when sucrose had already commenced to accumulate rapidly, this strongly substantiates these observations. Possible involvement of...

Sucrose Biosynthesis in Source Leaves

As outlined in the previous section, triose-P leaving the Calvin-Benson cycle can be exported from the plastid into the cytosol via the TPT and is then distributed between glycolysis and amino acid, lipid and sucrose synthesis (Figure 1.1). Sucrose is the major transport form of photoassimilates in higher plants, and as such forms the interface between pho-tosynthetically active source tissue and heterotrophic sink tissue, where it serves as an energy source for growth and provides building blocks for storage metabolism. During the light period, sucrose synthesis proceeds from triose-P and comprises seven enzymatic steps. The entry molecule is fructose-1,6-bisphosphate (FBP), which is formed by the condensation of two molecules of triose-P catalysed by the enzyme aldolase. In a subsequent reaction, a phosphate group is removed from the C1 atom of FBP by the cytosolic isoform of fructose-1,6-bisphosphatase (cytFBPase) to yield fructose-6-phosphate (F6P). This reaction is essentially...

Sucrose Transport In The Sugar Beet Plant

Sucrose Proton Symporter

Sucrose transport is critical for development and growth in most plant species. Biological membranes like the plasma membrane and the tonoplast are almost impermeable to uncharged and charged molecules under normal conditions unless there is a principle realised within these membranes rendering them selectively permeable to certain molecule species. Some specific sort of pores and or transport proteins have to be present to ensure selective permeability of these membranes for sucrose as well. Once sucrose has been formed within the cytosol of source (net exporting leaf mesophyll) cells, sucrose should be transported through membranes at different stages (fig. 1) 1) Sucrose may be transiently stored within the vacuoles of source leaf cells. Some tonoplast bound transport system for sucrose should be present. 2) Sucrose must cross the plasma membrane of source cells to enter the apoplasm via some transmembrane transport or exocytosis like process if it is not symplastically transported...

Photosynthesis Sucrose Flux Starch Pod Flower Number Soybean

Egli, D.B. and Bruening, W.P. (2001) Source-sink relationships, seed sucrose levels and seed growth rates in soybean. Annals of Botany 88, 235-242. Egli, D.B. and Bruening, W.P. (2004) Water stress, photosynthesis, seed sucrose levels and seed growth in soybean. Journal of Agricultural Science 142, 1-8. Goldschmidt, E.E. and Huber, S.C. (1992) Regulation of photosynthesis by end-product accumulation in leaves of plants storing starch, sucrose, and hexose sugars. Plant Physiology 99, 1443-1448.

The Pathway From Sucrose To Starch

3.2 Sucrose synthase We studied the expression of three isogenes encoding SuSl, SuS2 and SuS3 at the transcriptional level at different stages of seed maturation and in different rice organs (22). It has revealed that, although all of them are expressed mainly in seed, the expression of Susl is ubiquitous while that of Sus3 is exclusive in seed, and the expression sites and strengths of Sus2 seem to complement those of Susl, especially under the stress conditions such as anaerobiosis. The expression of Susl is quite unique it is upregulated by the availability of sucrose. These findings imply that Susl and Sus2 are house-keeping genes while Sus3 bears a specific role in the grain filling with starch. Sucrose is transported into sink organs form leaves through phloem. Enzymes located in phloem might regulate the sucrose concentration to force the sucrose flow from source to sink. Immunoblotting of SuSl and SuS2 in the extract of either shoot or root of etiolated seedling showed that...

Sucrose Synthesis

Starch and sucrose are the major end products of photosynthetic CO2 fixation. Carbon fixed during photosynthesis is either retained in the chloroplast and converted to starch or transferred to the cytosol in the form of triose phosphate through the operation of phosphate translocator and converted to sucrose (Fig. 3). Sucrose, which is the major transport form of reduced carbon in higher plants, is then either stored in the vacuole or transported to the other parts of the plant. This transported sucrose is either retained as such in sink tissues or, further metabolized to provide energy for growth and maintenance of cellular activities or converted to storage compounds (starch fats) in reserve tissues. The relative type and size of these carbohydrate pools vary dramatically during tissue development, between different plant species and within the same species subjected to different environmental conditions (66). This has generated considerable interest in the elucidation of regulatory...

Sucrose X

And transport through membranes are closely interacting to achieve the final goal , namely high sucrose concentrations. The review here focussed only on sucrose metabolism and transport, it fully neglected the influence of other nutrient and environmental factors on sucrose yield. However, as long as there is no clearcut picture of what happens to sucrose itself, no mechanistic model of influence by other factors can be reasonably developed. Therefore, focus on sucrose may be justified. Definitely, the future will lie in bringing together physiological mechanisms and agronomic factors to compose a whole plant model and to reveal quantitatively the network of metabolism, transport, growth and nutrition. Sugarcane is an interesting plant for plant physiologists in general, it hopefully may again give rise to new basic knowledge on plant function, as it happened when C-4 photosynthesis had been detected first in sugarcane. But research on the physiology of sucrose storage also has...

Transport Of Sucrose

Proton Translocator

Once sucrose is synthesized in mesophyll cells of source leaves, it has to be translocated to sink tissues. This transport occurs through phloem which contains elongated cells joined by sieve plates, consisting of diagonal cell walls perforated by pores. The single cells called sieve elements are surrounded by companion cells. Sieve elements and companion cells, in turn are connected to each other by many plasmodesmata. Photoassimilates generated in mesophyll cells diffuse via plasmodesmata to the phloem parenchyma cells. The further transport of photoassimilates from the phloem parenchyma cells to the sieve tubes can occur symplastically via plasmodesmata without involving translocators or apoplastically in which photoassimilates are first transported from the source cells via the phloem parenchyma cells to the extracellular compartment, the apoplast. This export does not require any energy as the concentration of sucrose is much higher in source cells than in the apoplast. The...

Methods and Molecular Tools for Studying Endocytosis in Plantsan Overview

Abstract Proteins of the endocytosis machinery in plants, such as clathrin and adaptor proteins, were isolated and characterized using combinations of molecular biological (cloning and tagging) and biochemical methods (gel filtration, pull-down assays, surface plasmon resonance and immunoblotting). Other biochemical methods, such as cell fractionation and sucrose density gradients, were applied in order to isolate and further characterize clathrin-coated vesicles and endosomes in plants. Endocytosis was visualized in plant cells by using both non-fluorescent and fluorescent markers, and by employing antibodies raised against endosomal proteins or green fluorescent protein-tagged endocytic proteins in combination with diverse microscopic techniques, including con-focal laser scanning microscopy and electron microscopy. Genetic and cell biological approaches were used together to address the role of a few proteins potentially involved in endocytosis. Additionally, biochemical and or...

Isolation of Clathrin Coated Vesicles

Plant clathrin-coated vesicles (CCVs) were isolated from cucumber and zucchini hypocotyls (Depta et al., 1991 Holstein et al., 1994). CCV components were protected against proteolysis using homogenization media composed of 0.1 M MES (pH 6.4), 1 mM EGTA, 3 mM EDTA, 0.5 mM MgCl2, a mixture of proteinase inhibitors and 2 (w v) fatty-acid-free BSA (Holstein et al., 1994). The crude CCV fraction (40 000-120 000 g pellet) was further purified by cen-trifugation in Ficoll sucrose according to Campbell et al., (1983) and then by isopycnic centrifugation in a sucrose density gradient using a vertical rotor (160 000 g, 2.5 h, Depta et al., 1991). CCV-enriched fractions (collected at 40-45 sucrose) were removed, pooled and pelleted. CCV fractions were stored at - 80 C for further use. Immunoblotting was performed using monoclonal antibodies against mammalian adaptins and clathrin. Confirmation of the presence of a P-type adaptin in plants was provided by dot and Southern blotting experiments...

Isolation of Plasma Membrane Lipid Rafts

Containing 4-6 1 (detergent-to-protein, w w) excess of Triton X-100 (no detergent was used in the control extractions). The final concentration of Triton X-100 was approximately 2 . Extractions were performed on ice with shaking at 100 rpm for 35 min. Extracts were adjusted to 1.8 M sucrose (Suc) TNE by addition of 3 volumes of cold 2.4 M Suc TNE. Extracts were overlaid with Suc step gradients 1.6-1.4-1.2-0.15 M and centrifuged at 240 000 g in a Beck-man SW50.1 rotor for 18 h at 4 C. DRMs were visible as off-white to white bands near the 1.2 1.4 and 1.4 1.6 M interfaces. Control fractions had a grey-green tinge. Fractions of 1 mL (0.5 mL above and 0.5 mL below the centre of the bands) were collected to harvest the DRM fractions and control fractions. Membranes were diluted with 4 volumes of cold TNE and pelleted at 100 000 g for 2 h in a Beckman 50Ti rotor.

Osmotic Adjustments and Controlling Factors

Intracellular water lost from the cell due to salt, drought and cold, leads to cellular dehydration. To prevent this and protect the cellular proteins, plants accumulate many organic compounds such as amino acids (proline), quaternary and other amines (glycine betaine and polyamines), a variety of sugars (mainly fructose and sucrose), sugar alcohols, complex sugars (like trehalose and fructans) and organic acids (oxalate, malate) (Valliyodan and Nguyen 2006). These metabolites with osmolytic function are also known as compatible solutes or osmoprotectants and may accumulate to high levels without disturbing the intracellular biochemistry (Ford 1984). By reducing the water potential within the cell, water loss is prevented and osmotic adjustment is facilitated (Delauney and Verma 1993).

Seed Research a Brief History

Gregor Mendel's studies on pea plants incorporated several seed traits, including the occurrence of wrinkled (rugosus) peas with a recessive mutation in the r locus. It is now known that the primary lesion in this locus results in rr embryos lacking starch branching enzyme I (SBEI) activity hence less amylopectin is synthesized during seed development, a build-up of sucrose and water ensues, and the embryo, which contains less than its full complement of reserves, shrinks during maturation drying (Wang and Hedley, 1991). The pioneering work of Mendel (1822-1884) also has an interesting tie-in with the pioneering work of Nobel laureate Barbara McClintock (1902-1992) almost a century later, which initially, like his own studies, was largely ignored. She discovered the transposable element, or 'jumping gene', and contended that certain autonomous elements within the maize gene are able to excise and become reincorporated into DNA elsewhere, resulting in a mutant allele (McClintock,...

Functionally intact cell organelles can be isolated from plant cells

In order to isolate cell organelles, the cell has to be disrupted only to such an extent that its intact organelles are released into the isolation medium, resulting in a cell homogenate. To prevent the liberated organelles from swelling and disruption, the isolation medium must be isotonic. The presence of an osmotic compound (e.g., sucrose) generates an osmotic pressure in the medium, which should correspond to the osmotic pressure of the aqueous phase within the organelle. Media containing 0.3 mol L sucrose or sorbitol usually are used for such cell homogenizations.

Various transport processes facilitate the exchange of metabolites between different compartments

Sucrose transported across the membrane against the concentration gradient. An example of this is the accumulation of malate in the vacuole (Figure 1.21C see also Chapter 8). Another example of secondary active transport is the transport of sucrose via an H+-sucrose symport in which a proton gradient, formed by primary active transport, drives the accumulation of sucrose (Figure 1.21C). This transport plays an important role in loading sieve tubes with sucrose (Chapter 13).

Units And Terminology Use For The Studies Of Photoautotrophic Micropropagation

In expressing concentrations of sugars, minerals and gelling agents such as agar, the unit of g l-1 (or g L-1) and mol l-1 (or mol L-1) are preferable. Percent ( ) cannot be substituted for g l-1 or mol 1-1, because the numerical value of percent can be calculated only when units of numerators and denominators are the same to each other. However, sugar and agar concentrations are often mistakenly expressed as 2 instead of 20 g 1-1. When concentrations of sucrose and glucose are, respectively, 34.2 g 1-1 and 18.0 g l-1, their molar concentrations are the same (0.1 mol 1-1), because sucrose (molecular weight 342) is a disaccharide and glucose (molecular weight 180) is a monosaccharide. Preferred unit (g l-1 or mol l-1) depends upon the purpose of work.

Sugars and Sugar Alcohols

Several studies have been attempted to relate the magnitude of changes in soluble carbohydrates to salinity tolerance. Parida and Das (2005) found out that carbohydrates such as sugars (glucose, fructose, sucrose, and fructans) and starch are accumulated under salt stress. Furthermore, Megdiche et al. (2007) and Geissler et al. (2009a) proved that Cakile maritima and Aster tripolium plants accumulate high amounts of total soluble carbohydrates and Pro at high salinity (400 and 500 mM NaCl, respectively). The major functions of sugars and sugar alcohols are osmoprotection, osmotic adjustment, carbon storage, and radical scavenging (Adams et al. 2005 Ashraf et al. 2006 Messedi et al. 2006 Lee et al. 2008 Ahmad and Sharma 2008). Furthermore, there is a discussion about that they serve as molecular chaper-ones (Hasegawa et al. 2000 Liu et al. 2006). There is a difference between starch and sugar accumulation in short- and long-term reaction (da Silva and Arrabaca 2004). In short-term...

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...

Conventional IEF in Soluble Amphoteric Buffers

CA-IEF was born as a preparative technique in a liquid phase, exploiting large-size columns filled with a sucrose density gradient as an anticonvective medium. When reports appeared on its use in PAG strips or thin tubes 20 , its popularity grew exponentially untill it became a household item in every lab. Although there are four major commercial brands available today, the formulas and general properties of only three of them are known Servalyt, Ampholine, and Pharmalyte (Figure 2.3), with the Bio-Lyte product (from Bio-Rad) being undisclosed. It can be seen that Ampholine, still made according to the original patent by Vesterberg 3 , comprises aliphatic oligoamino oligocarboxylic acids, obtained by reacting mixtures of oligoamines (3 to 9 nitrogen long) with unsaturated acids, such as acrylic and itaconic acids. Servalyt is made by first preparing oligoamines via reaction of ethylene imine with propylene diamine and collecting by distillation all products up to 400 Da in size. Such...

Carbon physiology of mycorrhizal symbioses

A graphic experimental demonstration of this behaviour was provided by Lewis and Harley (1965), using excised mycorrhiza. They showed that if 14C sucrose was applied to the cut axis, 14C carbohydrate was translocated to the tip and accumulated particularly in the fungal sheath in the form of the fungal carbohydrates trehalose, mannitol and glycogen, carbohydrates not readily used by the host tissues. These examples emphasize a similar pattern to rust fungi and have indeed been accepted widely as the most likely behaviour in all mycorrhiza. However, caution is necessary, because it does not seem so easily applicable to vesicular-arbuscular mycorrhiza (see Smith, S.E. and Gianinazzi-Pearson, 1988), although lipids, glycogen granules, polyols and trehalose have at times and to some extent been found in their hyphae. It is clear that more investigation is needed, especially into the substances which become labelled in vesicular-arbuscular fungi and into the actual carbonaceous substances...

Translocation in mycorrhizal systems

Translocation in orchid fungi was first investigated by S.E. Smith (1967), using orchid seedlings as receptors and the hyphae of species of Rhizoctonia as translocators. Carbohydrate absorbed by the fungus from the culture medium appeared in the hyphae as trehalose, and in some strains as mannitol also. In the seedling tissue these fungal sugars diminished and sucrose was formed, i.e. the reverse of the behaviour in ectomycorrhiza.

Interference with crop management and handling

Some weeds can make the operation of agricultural machinery more difficult, more costly, or even impossible. The presence of weeds within a crop may necessitate the need for extra cultivations to be introduced. This often leads to crop damage, reduced yields and increased pest and disease occurrence, although in sugar beet crops, where inter-row cultivation is often carried out and has previously been associated with yield loss, recent findings suggest that careful implementation can result in no loss of root yield or sucrose content (Dexter et al., 1999 Wilson and Smith, 1999). This is possibly due to the development of tillage equipment that carries out more shallow cultivation

The mechanisms regulating NO3 uptake

Experimentally, NO3- uptake can be increased in parallel with the growth rate by increasing light intensity (e.g. Gastal and Saugier 1989). The diurnal regulation of NO3- uptake (higher rate during the light period, lower rate during the dark period) has been considered as a specific example of its regulation by light (Delhon et al. 1995). The stimulation of NO3- uptake by light is attributed to photosynthesis, since it could be prevented by decreasing the atmospheric CO2 concentration (Delhon et al. 1996). Moreover, the addition of carbohydrates to the nutrient solution is known to increase NO3- uptake (Hanisch Ten Cate and Breteler 1981). Blocking phloem translocation in soybean plants by means of stem girdling led to a decline in the rate of NO3- uptake, which is partially restored by adding glucose to the nutrient solution (Delhon et al. 1996). No consensus exists that an energetic shortage might occur in roots, even at night, and an increased energisation of the plasma membrane...

Cell Cycle Regulated Gene Expression in Plants

When interpreting experimental data from cell cycle time courses, it is worthwhile considering potential pitfalls inherent with existing synchronization methods Inhibitor-based synchronization methods are susceptible to non-specific or unexpected side effects. For example, the commonly used fungal toxin Aphidicolin, which inhibits replicative DNA polymerases, will elicit some of the cellular responses controlled by the mechanisms that monitor the completion of DNA replication. A good example is the observation of S-phase induction of cyclin B1 1 (but not of other cyclins of the cyclin B1 clade) expression in Aphidicolin-treated Arabidopsis cells, but not in cells synchronized by withdrawal and provision of sucrose (Menges et al. 2005). Cyclin B1 1 expression has been shown to be specifically induced by DNA damage and incomplete replication check points (Culligan et al. 2006). Other inhibitors, including the mitotic spindle inhibitors (propyzamide, colchicine, amiprophos methyl,...

Broad Spectrum Organic Matter Mediated Suppression

Perhaps the most important feature of organic-matter mediated general suppression is its capacity to act against most, if not all, major soilborne pathogens of food and fibre crops. Since root disease problems in the field rarely involve a single pathogen, enhancing the suppressive potential of a soil with organic matter is one of the only non-chemical techniques available to control a suite of pathogens. This does not mean that manipulating organic matter to manage several pathogens is a simple matter. When pathogens which are good primary saprophytes but poor competitors are involved (e.g. Pythium and Fusarium), the fact that they may multiply on fresh organic matter before being suppressed must be taken into account when designing application strategies. In the case of Rhizoctonia, which has a high competitive saprophytic ability due to its capacity to degrade cellulose as well as simple sugars, organic-matter mediated general suppression is often insufficient to achieve control...

Equilibria in the Soil Solution

The plethora of many experimental chemistry papers dealing with hydrous oxides and their control of other metal solubilities in relation to redox and pH should not distract attention from the equally important role of microorganisms and soluble organic materials. It has long been known that soil microorganisms can significantly alter the pH for the Mn(II) Mn(IV) equilibrium (Bromfield, 1956). Similarly, reduction of iron compounds in the formation of gley soils is very dependent on a supply of readily oxidisable organic matter. Couto et al. (1985) studied oxidation - reduction processes in a Brazil oxisol with a seasonal water table. Although the water table stood at 0.4-2 m of the surface for more than 90 days each year there was little pedological evidence of gley formation and bright platinum electrodes demonstrated that Eh values stayed within the range 500-700 mV. Fe(II) formed in samples from below 40 cm only when incubated with sucrose. The authors interpreted these data as...

Materials and Methods

Two-phase portioning was performed using a 6.4 (w w) Dextran T500 PEG3350 mixture (Larsson et al., 1987). Sucrose density gradient centrifugation was performed essentially as described by Ferrol and Bennett (1996). For proteolysis, the microsomes were incubated with 100 g mL-1 of proteinase K for 0-60 min at 30 C in the absence or presence of 0.1 (v v) Triton X-100.

Results and Discussion

Two-phase partitioning, sucrose density gradient centrifugation, and GFP imaging were used to investigate the subcellular localization of CmERS 1. The results demonstrate that CmERSl is predominantly localized to the ER (Fig. 1). Our data provide experimental evidence for the ER localization of an ERS-type receptor. These observations, together with the ER localization of AtETR1, support the deduction that the ER may play a central role in ethylene perception and early signal transduction (Chen et al., 2002 Gao et al., 2003).

The VAZ Pathways Story

Of course, the instrumentation and analytical methods available 45 years ago were crude by today's standards. I used preparative columns packed with powdered sugar to separate the xanthophylls of saponified extracts of leaves. Saponification removed chlorophyll that these columns could not resolve from xan-thophylls. To assure complete recovery of xanthophylls after saponification, the xanthophylls were washed into ethyl ether instead of petroleum ether. Safety precautions were not what they are today and I was lucky not

Artemisia tridentatasunflower Family

Many of the younger twigs are green and capable of photosynthesis. In fact, the terns produce nearly as much sugar as the threadlike leaves, especially in the spring, when the soil is moist from winter rains. Later in the season, the shrubs lose many of their leaves as the soil d es out.

Keeping It Simple Why Unicells Are Cool

Many of the abovementioned limitations do not apply to unicellular photosyn-thetic organisms, such as algae, and the compartmentation issue can be addressed by investigation of prokaryotic photosynthetic organisms, such as cyanobacteria which are evolutionary connected to plastids and thus might serve as models for plastid metabolism. A prime example for the dissection of a relatively complex metabolic pathway in photosynthetic organisms is the reductive pentose phosphate pathway, also known as the Calvin cycle. In series of milestone papers in the late 1940s and early 1950s, using unicellular algae such as Scenedesmus and Chlorella, as well as land plant leaves, the path of carbon in photosynthesis was elucidated. In a landmark paper, it was shown that the first labeled organic carbon compound found in Scenedesmus cells that were allowed to photosynthesize in the presence of labeled carbon dioxide for five seconds was phosphoglyceric acid and that the first free carbohydrate to...

Concepts And Definitions

Ideally, photoautotrophic micropropagation should be segregated from sugar-free micropropagation. However, in this chapter, while we will define photoautotrophy as the plant nutritional type where only endogenous carbohydrate is used as the energy source, for all practical purposes photoautotrophic micropropagation refers to micropropagation with no sugar added to the medium. Sugars and other carbohydrates may be significant components of agar and other gelling agents, but perhaps it is reasonable not to consider it as an exogenous carbohydrate source in the practical definition of photoautotrophic micropropagation.

Transcellular Osmosis and Polar Water Permeability

Sucrose solution, water moves transcellularly from chamber A to chamber B. The rate of the flow is proportional to the osmotic pressure (po) in B. The TCO constant (K) defined by Kamiya and Tazawa (1956) is obtained by dividing the initial rate of water flow (Jv) by the external osmotic pressure (po) that drives the flow. Namely, Later, Dainty and Ginzburg (1964a) found in Chara that hydraulic conductivity decreased markedly with an increase in the external sucrose concentration. They found that the inhibitory effect of the external osmolality cannot be attributed to the sweeping away effect. The inhibitory effect of the external osmotic pressure on hydraulic conductivity was reconfirmed by Kiyosawa and Tazawa (1972) in Nitella flexilis.

SOS Genes and Salt Tolerance

The salt overly sensitive (SOS) ion homeostasis and signaling pathway is another well-characterized abiotic stress response in Arabidopsis. The SOS1, SOS2, and SOS3 loci were first identified through forward genetic screens for salt-hypersensitive growth. SOS1 is a plasma membrane Na+ H+ antiporter that is essential for Na+ efflux from roots. SOS2 belongs to subgroup 3 of the sucrose non-fermenting-related kinases (SnRK3s). SOS3 is a myristoylated calcium-binding protein that likely responds to salt-induced Ca2+ oscillations in the cytosol. The SOS signaling pathway functions in regulating Na+ homeostasis and salt tolerance in Arabidopsis. High Na+ stress triggers a calcium signal that activates the SOS3-SOS2 protein kinase complex, which then stimulates the Na+ H+ exchange activity of SOS1 at the plasma membrane. SOS2 also activates Na+ H+ (AtNHX) exchangers on the vacu-olar membrane (Zhang et al. 2004b). Increased expression of the Arabidopsis tonoplast membrane Na+ H+ antiporter,...

The Biochemical CO2 Pump of C4 Photosynthesis Share of Labor Between Two Cell Types Causing Massive Flux of Metabolic

CO2 fixation by Rubisco in bundle sheath cells yields two molecules of phospho-glycerate (3-PGA). The reduction of two 3-PGA to two triose phosphates requires two NADPH. However, the oxidative decarboxylation of one malate yields only one NADPH (and linear electron transport is insignificant in bundle sheath cells), hence one molecule of 3-PGA has to be exported to the MC plastids where it can be reduced to triosephosphate (TP). Two thirds of the generated triosephosphate then need to be re-exported to bundle sheath plastids for regeneration of ribulose-1,5-bisphosphate the remainder can be exported as sucrose to sink tissues.

Higher Level Control of Organ Size and Plant Wide Integration

Changing not the number of developing sink organs but their sink strength can also influence their final size apoplastic expression of a yeast invertase, which cleaves sucrose into glucose and fructose and is thought to influence sink strength, was found to increase tuber size in potato tubers (Sonnewald et al. 1997). However, the effect was compartment-specific, and targeting in-vertase to the cytosol actually had the opposite effect.

Primary Metabolites Of Carum Carvi

Mono-, oligo- and polysaccharides found in all parts of the plant serve as a temporary reserve material. The monosaccharides identified in caraway fruits, leaves and spare tissues are hexoses glucose and fructose. Main reserve disaccharide is saccharose (sucrose), found in quantity 1 and 3 of fresh plant weight in fruits and leaves respectively. The changes in main mono- and disaccharides content during caraway two years vegetation period is described in details by Hopf and Kandler (1976). Other disaccharides found in the seeds in minor amounts are trehalose, glucosyl mannose and mannityl-1- -glucose. The most interesting trisaccharide of Carum is perhaps umbelliferose (Figure 1a), an isoraffinose typical to umbellifers, found in all parts of the plant and serving as a temporary reserve material similar to sucrose. It occurs in greater amounts than sucrose only in the ripe fruits and is not preferentially accumulated in any particular vegetative organ. Physiology of this sugar, its...

Inoculation Techniques

Petri plates are probably the most extensively used method of ectomycorrhiza synthesis. Wong and Fortin (1989) described a Petri dish technique that avoids limitations of previous ones. In Petri dish filled with sugar-free agar medium, two sheets of nylon membrane sandwiched the root and were overlaid with a sheet of filter paper to keep the exposed surface of the roots moist. Cotton rolls were placed along the opposite edge of the Petri dish to absorb water which condensed during incubation. The filter paper was removed and the fungal plugs were placed on the membrane beside root laterals. Peterson and Chakravarty (1991) differentiated between simple system, divided Petri plates, sandwich technique, and nylon mesh method. Sandwich technique (mycelial plugs placed on cellophane sheets) was a method of synthesis experiments conducted by Langer et al. (2008) on Populus tremula plantlets. Mixture of vermiculite and peat seems to be a suitable substrate for Petri dish synthesizing system...

Identification of alterations in the expression of selected genes in response to artificially induced dormancy release

The first attempt to identify alterations in gene expression during early stages of dormancy release in grape buds was reported by Or and co-workers in 2000 (Or et al. 2000b). A comparison of RNA populations from HC-treated and control buds by differential display revealed a transcript for a Sucrose Non Fermenting (SNF)-like protein kinase that was upregulated following induction of dormancy release by HC. Evidence at the time from other systems suggested that SNF-like protein kinases may function as stress pseudoreceptors in yeast and mammals (Trewavas and Malho 1997). Accordingly, the parallel transcriptional regulation of a few plant SNF-like kinases by stress-related stimuli was recorded (Anderberg and Walker-Simmons 1992, Hardie 1994, Trewavas and Mahlo 1997). Therefore, it was suggested that the grape dormancy breaking-related protein kinase (GDBRPK) might be involved in the perception of a stress signal induced by HC (Or et al. 2000b).

Carbon Partitioning in Mesophyll Cells

Figure 1.1 Photosynthetic carbon metabolism in mesophyll cells of source leaves. Dotted lines indicate the night path of carbon export from the chloroplast when starch mobilisation occurs. Abbreviations FBP, fructose-1,6-bisphosphate F6P, fructose-6-phosphate G6P, glucose-6-phosphate G1P, glucose-1-phosphate ADP-Glc, ADP-glucose UDP-Glc, UDP-glucose S6P, sucrose-6-phosphate cytFBPase, cytosolic fructose-1,6-bisphosphatase SPS, sucrose-phosphate synthase TP, triose phosphate Figure 1.1 Photosynthetic carbon metabolism in mesophyll cells of source leaves. Dotted lines indicate the night path of carbon export from the chloroplast when starch mobilisation occurs. Abbreviations FBP, fructose-1,6-bisphosphate F6P, fructose-6-phosphate G6P, glucose-6-phosphate G1P, glucose-1-phosphate ADP-Glc, ADP-glucose UDP-Glc, UDP-glucose S6P, sucrose-6-phosphate cytFBPase, cytosolic fructose-1,6-bisphosphatase SPS, sucrose-phosphate synthase TP, triose phosphate of triose-P by either of these processes...

By the Inner Cortex Cells Located near the Unloading Phloem Elements

Heterotrophic plant cells, such as root and suspension culture cells, as well as dark-grown plant cells are dependent on external nutrient supply. Sucrose starvation induces autophagy and formation of autolysosomes in plant cells (Yano et al. 2004). Within the plant body, phloem elements redistribute assimilates synthesized in leaves and transport them towards sink tissues. One of the best studied sink tissues is that of root apices. In root apices, unloading phloem elements release large amounts of sucrose, literally flooding the neighboring cells. Sucrose is transported from cell-to-cell symplastically via plasmodesmata (Oparka and Cruz 2000 Baluska et al. 2001c, Sadler et al. 2005). However, calculations made for maize root apices revealed, that the number of plasmodesmata can not satisfy the high demand for sucrose established by their large meristems and by the root caps (Bret-Harte and Silk 1995). Another popular scenario is that sucrose is enzymatically cleaved by cell wall...

In vitro conservation

Geetha etal. (1995) and Nirmal Babu et al. (1994, 1999a,b) reported conservation of cardamom germplasm in in vitro gene bank by slow growth. The above workers carried out various trials to achieve an ideal culture condition under which the growth is slowed down to the minimum without affecting the physiology or genetical make up of the plant. The slow growth is achieved by the incorporation of agents for increasing the osmotic potential of the medium, such as mannitol. They found that half strength MS without growth regulators and with 10 mg l each of sucrose and mannitol was the best for in vitro storage of cardamom under slow growth. By using the above medium in screw capped vials the subculture interval could be extended to one year or more, when incubated in 22 2 C at 2500 lux of light and at 10 h photoperiod. Low temperature storage at 5 C and 10 C was found to be lethal for cardamom, as the cultures did not last more than three weeks (Geetha et al. 1995).

Crucial First Step in Establishing Chloroplast Cytoplasm Metabolic Connection Evolution of the Triose Phosphate

Considering the situation of a free-living, coccal cyanobacterium, the presence of a triosephosphate phosphate antiporter in its plasma membrane would very likely have been detrimental because it would have allowed for the efflux of triose phosphates from the cyanobacterium in the presence of suitable external concentrations of orthophosphate. It is thus reasonable to hypothesize that the triosephos-phate phosphate antiporter was not introduced by endosymbiotic gene transfer from the cyanobacterium, but it was derived from a pre-existing host protein that was directed to the cyanobacterial plasma membrane (now the inner plastid envelope membrane) after the endosymbiont had entered the host cell. This hypothesis was recently tested by phylogenomic and phylogenetic analysis of genomic and EST-sequence data from a broad range of organisms. It was shown that the plastidial triosephosphate phosphate translocators evolved from transport proteins of the eukaryotic endomembrane system,...

Composition of the Medium

Sucrose is the most common carbon source in culture media, although the percentage used with different species varies and is generally determined by empirical manipulation of one or a combination of the existing culture media. Basal media such as MS (Murashige and Skoog 1962) or NLN media (Lichter 1982) with slight modifications are commonly used with Brassica and other species. With cereals, media such as A2 (Touraev et al. 1996b) and MMS3 (Hu and Kasha 1997) are also used. Nitrogen, phosphorus and calcium sources are also adjusted in these media. As for mineral micronutrients, it has been shown recently that copper sulphate increases the percentage of green plant regeneration in the very responsive winter-barley cultivar Igri (Wojnarowicz et al. 2002). Studies with this cultivar have also shown a marked short- and long-term influence of iron in the culture medium on isolated microspores used for embryogenesis. Quite frequently, the same composition adjusted for anther culture is...

Current Work In Our Laboratory Isolation of Fungal Effector Molecules

Stage aimed at interfering with the adhesion between the plant cell wall and plasma membrane, which is required for the expression of wall-associated responses. In order to identify the fungal molecule(s) responsible for this effect, we are using a Saccharomyces cerevisiae-based signal sequence trap technique in which 5' enriched cDNAs from developing rust fungal basidiospores are fused in frame with a truncated yeast invertase lacking an initiator methionine and signal sequence. cDNAs encoding the N-termini of proteins capable of directing this fusion protein to the secretory pathway are selected for because of their ability to allow an invertase-deficient strain of yeast to grow on sucrose medium and are likely to encode proteins relevant to the initial pathogenesis process, including the adhesion-reducing mole-cule(s). This screen may also be helpful in cloning peptide cell death elicitors produced by the cowpea rust fungus (D'Silva and Heath, 1997) that are produced following...

Mutant isolation and characterisation

Reciprocal crosses between the mutants and wild-type (wt) lines revealed that none of the mutants was allelic and that they were recessive, with the exception of 4 which was semi-dominant. From their behaviour the mutants appear to fall into two classes. The fun 1 and fun 2 mutants not only flower early in SD but also flowered early when grown in darkness on agar supplemented with sucrose. For these mutants, flowering appears to be more or less independent from the light treat-

The Cell Cycle in Roots and the Core Components

Modulation of CDK activity is also achieved by interaction with proteins of the interactor of CDK (ICK) Kip-related protein (KRP) and SIAMESE (SIM) families (Dewitte and Murray 2003 Churchman et al. 2006 Inze and De Veylder 2006). The ICK KRP family contains seven members (ICK KRP1-7) (Vandepoele et al. 2002), whereas the SIM subfamily contains five members (Peres et al. 2007) in Arabidopsis. Global transcriptomic analysis in synchronized Arabidopsis cell cultures reveals that ICK KRPs show different patterns of regulation during cell cycle reentry and cell cycle progression, with sequential peaking in cell cycle phases (Menges et al. 2005). Interestingly, ICK KRP2 is expressed at high levels in sucrose-starved cells, declines on cell cycle resumption, and does not show any later regulation during subsequent cell cycle progression, suggesting a specific role in cell cycle reentry (Menges and Murray 2002 Menges et al. 2005). Gene expression analysis of ICK KRPs genes in Arabidopsis...

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.

Are fruits of the same size and color different in irondeficient and control plants

A recent paper has provided evidence that the chemical composition of peach fruits having the same size, color and firmness, but coming from Fe-deficient and Fe-sufficient trees, is indeed different (Alvarez-Fernandez et al., 2003a). Both types of fruits had similar H+ titratable acidity ratios, suggesting that maturity was similar. The major finding in this study was a change in the total sugars to total organic acids (w w) ratio, which decreased significantly with Fe deficiency, from 12 to 9 in the cultivar 'Carson' and from 10 to 7 in the cultivar 'Babygold' (Figure 4-3 Alvarez-Fernandez et al., 2003a). This change would likely modify the organoleptic characteristics of fruits, probably decreasing the value of the crop. In both cultivars, Fe deficiency generally caused moderate increases in organic anion concentrations, which were larger for succinate and quinate (35-52 and 33-48 , respectively), than for citrate and malate (17-20 and 11-12 , respectively Alvarez-Fernandez et al.,...

Size Control of the Proximal Root Apical Meristem and the Mitotic Cell Cycle

Modulates the onset of endoreduplication (Schnittger et al. 2002a Boudolf et al. 2004, 2009). CCS52A1, an activator of the anaphase complex, is able to target CYCA2 3, a mitotic cyclin, for destruction in the elongation zone of the root (Boudolf et al. 2009) and elevating CYCA2 3 levels delayed the onset of cell elongation (Ishida et al. 2010). These arguments indicate that mechanisms associated with the G2-M transition are putative targets for elongation onset pathways to interfere with the cell cycle. Nevertheless, this does not exclude that factors involved in the G1-S transition that prime cells for a mitotic division by linking the different cell cycle phases are important targets. Indeed G1 cyclins, such as D-type cyclins, are able to stimulate the G1-S transition and to prime cells for a mitotic cell cycle (Schnittger et al. 2002b Dewitte et al. 2003, 2007 Qi and John 2007), thereby preventing endocycles and elongation. In this respect, one link to the core cell cycle machinery...

Sugar sensing and response

G proteins also have a role in sugar transport. A Golgi-localized hexose transporter, suppressor of G p (SGB1), was identified from a genetic screen for AGB1 modifiers that could suppress the altered cell division in the hypocotyl and glucose hypersensitivity of the agbl-2 mutant (Wang et al., 2006a). SGBl has a similar tissue expression pattern as that of AGBl, and its expression increases in the presence of D-glucose or sucrose. Interestingly, in the absence of exogenous sugar, SGB1 traffics to small vesicular compartments suggestive of the trans-Golgi network and the addition of sugar collapses these vesicles to the Golgi proper. Loss-of-function mutants of SGBl phenocopy agbl-2 mutants, whereas overexpression of SGBl suppresses the cell division and sugar hypersensitivity of agbl-2 mutants. These findings provide genetic evidence that SGB1 acts together with AGB1 in regulating sugar transport. These findings establish SGB1 as the first potential effector protein for AGB1, although...

Cell Proliferation Outside the Root Apex Reactivation of the Pericycle

Level of KRP proteins, which can inhibit CYCD CDKA activity, suppresses lateral root formation and conversely, mutations in KRP2 stimulate lateral root formation (Himanen et al. 2002 Sanz et al. 2011). While CYCD2 1, is induced by sucrose, as is the related CYCD4 1, KRP2 levels are controlled by auxin, enabling auxin to control CYCD2 1 activity post-translationally (Himanen et al. 2002 Sanz et al. 2011). It is still an open question whether these CYCD-related pathways are targets of the SLR IAA14-ARF7-ARF19 pathway or if they control the basal sensitivity toward auxin by intervening with the initial cell cycle progression at the pericycle xylem pole (Casimiro et al. 2003).

Genetics and Physiology of the Floral Transition

Further, nutrition also has an impact on flowering time. It is known that sucrose has an effect in Arabidopsis. High levels of sucrose cause a delay of the transition to the reproductive phase, allowing for more meristems to be allocated to further growth (Ohto et al, 2001). In most cases, different types of stress shorten the time to flowering. It is not known till date whether these factors act through one of the described pathways or if there are additional unidentified pathways.

Sink Strength In Sugar Beet

The old source leaves supply predominantly the core region, whereas the youngest source leaves supply first of all the outer regions of the beet root with photoassimilates and nitrogen (140). The phloem parenchyma and meristematic cells of the supernumerary cambia are served first because of their vicinity to the phloem elements, the large storage parenchyma cells between the cambia are served relatively late, the core region of a beet root is served latest. However, since the core region is supplied over the longest time period, the sugar content is highest in this region (28, and literature cited therein). Consequently, increase in cell number, cell growth and accumulation of sucrose are the minimum stages characterising the beet taproot as a sink.

Conclusion And Future Strategies

With regard to sucrose accumulation in beetroots, not only the sucrose metabolising enzymes such as SuSy and SPS have to be considered in future experiments on the molecular genetics level as factors determining sink strength and sucrose accumulation capacity. In analogy to the situation at the source site, future experiments down to the molecular genetics level (including the generation of transgenic plants) should pay attention to the possible influence of cell wall bound acid invertase within the different sink tissue regions, the influence of the number (and specific activity) of the plasmalemma and tonoplast bound sugar transporters and the influence of hormonal control over their development as well as of sugar sensing. An important tool in this regard could be the comparison of different subspecies of Beta vulgaris, e.g. vulgaris var. alba (fodder beet, 3-5 sucrose) vs. altissima (sugar beet, 15-20 sucrose) or even of sugar beet with the presumed mother Beta vulgaris ssp....

A loss of intermediates of the citrate cycle is replenished by anaplerotic reactions

Another important substrate of mitochondrial oxidation is glutamate, which is one of the main products of nitrate assimilation (section 10.1) and, besides sucrose, the most highly concentrated organic compound in the cytosol of many plant cells. Glutamate oxidation, accompanied by formation of NADH, is catalyzed by glutamate dehydrogenase located in the mitochondrial matrix (Fig. 5.11). This enzyme also reacts with NADP+. NADP-glutamate dehydrogenase activity is also present in plastids, although its function is yet not understood.

Subcellular Localization of BP80 and its Homologues

Investigations on the location of BP-80 and its homologues have also been performed on non-storage protein producing cells. Immunogold electron microscopy and subcellular fractionation approaches have shown that VSR proteins are not present in the vacuolar membrane (Ahmed et al. 1997 Paris et al. 1997 Sanderfoot et al. 1998). BP-80 has been localized to the Golgi apparatus and to a putative lytic PVC in pea root tip cells (Paris et al. 1997). AtELP, a BP-80 homolog from Arabidopsis equivalent to VSRAt1 (Ahmed et al. 1997) has been localized to the Golgi apparatus and to a putative PVC characterized by 100 nm diameter tubules in Arabidopsis root tip cells (Sanderfoot et al. 1998). However, these tubular structures were also consistent with the appearance of TGN (Robinson et al. 2000). Subcellular fractionation demonstrated that AtELP in both Arabidopsis (Ahmed et al. 1997 Sanderfoot et al. 1998) and transgenic Arabidopsis plants expressing a mammalian Golgi enzyme...

Tissue Culture Imposes a Stress to Cultivated In Vitro Cells

Other than manipulation of the medium composition, a wide range of modifications have been investigated to develop the methodology enabling one to obtain the desired response in a particular plant species. The beneficial, or crucial, role of stress treatments has been well documented in the induction of somatic embryogenesis (SE). The addition of exogenous 2,4-D is one of the key steps in the induction of SE and, in particular, in the acquisition of embryogenic competence in many plant cells cultured in vitro. However, the role of 2,4-D is controversial, because it has been considered to function as a stress substance rather than as a phytohormone, triggering the acquisition of embryogenic competence (Kikuchi et al. 2006). In addition to 2,4-D, abscisic acid (ABA) may act as a stress-causing agent for inducing SE in carrot (Kikuchi et al. 2006). The important role of ABA signalling in the induction of SE has been confirmed by a mutant study in which ABA-hypersensitive and...

Acclimation of Root Growth Towards Alterations of Light Intensity

Shown that a very pronounced and characteristic reaction of root growth occurs when light intensity is increased (Nagel et al. 2006) During the first three hours after increase of light intensity by a factor of five, a characteristic fluctuation of root tip growth velocity was observed that was connected to parallel decreases and increases of expansion within the meristematic zone and the zone of cell elongation. The fluctuations were caused by a superposition of a transient, hydraulic decrease of growth activity due to increased transpiration and an accelerating increase of growth activity induced by sucrose import. Experiments with tobacco plants that had a decreased activity of sucrose-phosphate phosphatase (Chen et al. 2005) showed far less pronounced growth reactions. As the total increase of root growth activity by a factor of four within four days exceeded the increase of shoot growth acceleration by far, a significant shift of root-shoot-ratio was detected as a consequence of...

Establishment of Aseptic Cultures

Nodal explants of one-month-old A mangium aseptically germinated seedlings are cut into small segments 2-3 nun in length and then placed in lull-strength MS medium supplemented with 37r sucrose (w v), 0.6 bacteriological agar (w v), and growth substances. They should be incubated in a controlled environment culture room at 20 C with a photoperiod of 18 hours. One month after inoculation explants should be transferred onto fresh medium of the same composition.

Carbohydrate Metabolism

In eukaryote cells, carbohydrate metabolism is one of the major bioenergetic pathways utilizing simple sugars through glycolysis, the tricarboxylic acid cycle (TCA) and oxidative phosphorylation. The hexose transporters carry different hexoses (including glucose) across cell membranes. ESTs of this transporter have been identified in P. involutus-B. pendula association (2-14 days) potentially indicating increased metabolic activity during the early physical contact stage (Le Quere et al. 2005). Sorbitol dehydrogenase expression was repressed in P. involutus from the second to the eighth day of interaction. Together with the aldose reductase, this enzyme converts sorbitol (sugar alcohol) into fructose, allowing for further glucose production without ATP consumption. Sorbitol dehydrogenase down-regulation may indicate the fungus's preference for the glucose pathway.

Variation of Root Growth

Finally, the enormous relevance of carbohydrate metabolism for short-term growth variations is also seen in roots. As mentioned above, plants with decreased activity of sucrose-phosphate phosphatase reacted much slower than wild-type plants towards an increase of light intensity (Nagel et al. 2006). Experiments with excised root systems, that continued growth without being provided with photosynthates from the shoot as long as sucrose was available from the growth medium, supported the hypothesis that carbohydrate availability is crucial for the intensity of root growth. A direct correlation of root growth intensity with carbohydrate concentration of the growth zone has also been described for Arabidopsis thaliana (Freixes et al. 2002). Yet, the small-scale distribution of growth across the root growth zone is not connected to carbohydrate concentrations, but probably regulated by carbohydrate deposition rates and deposition rates of other growth substrates such as mineral nutrients...

Increased Content of Atmospheric CO2

For a number of species, results have shown that photosynthesis is increased by an elevation of atmospheric CO2 (Poorter and Navas 2003 Long et al. 2004 Ainsworth and Long 2005). The degree of photosynthetic amelioration depends on interaction with other factors such as temperature (Turnbull et al. 2002) and nutrient availability (Kruse et al. 2003). In growing leaves, assimilation is often stimulated more strongly than in fully differentiated leaves (Pearson and Brooks 1995 Miller et al. 1997 Wait et al. 1999), which leads to increasing contents of starch, sucrose, glucose and fructose (Poorter et al. 1997). If plants are exposed to elevated CO2 for a longer time, acclimation is observed and assimilation decreases gradually (Stitt 1991 Ainsworth et al. 2003). Growth usually reacts in a less-pronounced way towards elevated CO2, but data reported in the literature shows an enormous variability (Poorter and Navas 2003). Similar to biomass growth, crop yield from studies under elevated...

Will increased photosynthetic efficiency lead to increased yield in rice

Plant mass is primarily derived from photosynthesis and so it is surprising that final plant mass (yield) and photosynthetic rate of leaves are often not well correlated. The rate of plant respiration and loss of plant matter through detachment also influence yield. The lack of correlation also reflects the fact that photosynthate availability is just one of many signals that affect plant growth and development. Plants grown in elevated carbon dioxide normally have increased yield, which tells us that increasing the availability of photosynthate is likely to increase yield, though perhaps not as much as might be expected. In redesigning photosynthesis for increased yield, we can focus on the inputs, fundamental mechanisms, or outputs. Given the importance of the relationship between photosynthesis and plant growth, this chapter focuses on the outputs of photosynthesis and their immediate use, especially the enzyme sucrose-phosphate synthase (SPS). Plants that are transformed to...

Sugars as Signalling Molecules

Almost two decades ago, Sheen (1990) used photo-synthetic gene promoter reporter gene fusions to show that seven maize photosyn-thetic genes were repressed by glucose or sucrose in a maize protoplast system. Further evidence of feedback control of photosynthetic gene expression was obtained in experiments where a yeast invertase was expressed in tobacco and Arabidopsis (von Schaewen et al. 1990) or tomato (Dickinson et al. 1991). This resulted in the accumulation of hexoses in the leaves of the transgenic plants, which caused feedback inhibition of photosynthesis. Other genes that are required for photosynthesis and are regulated by sugars include those encoding the ribulose 1,5-bisphosphate carboxylase oxygenase (RuBisCo) small subunit, chlorophyll a b binding protein (CAB) and thylakoid ATPase delta subunit (Harter et al. 1993 Krapp et al. 1993 reviewed in Sheen 1994 Halford and Paul 2003). Other glucose-repressed genes include those encoding isocitrate...

Proteomics of Subcellular Compartments

The characterization of proteomes at different subcellular locations is of prime importance for a complete understanding of plant functions, biosynthetic, and signaling pathways. The use of subcellular fractionation permits a simplification of the proteome and provides a practical step toward the ultimate description of the entire proteome. The efficiency of proteomics technology relies essentially on the quality of the biological sample analyzed thus sample preparation becomes the most critical step in subcellular compartment proteomics. Despite the fact that Arabidopsis was not the most appropriate plant on which to carry out subcellular fractionation, a number of procedures have been developed to enrich and purify organelles. The choice of starting material is important to prepare highly purified organelles. For example, the choice of leaf tissue to prepare chloroplasts seems obvious 14-16 . Mitochondria are better purified from cell suspensions 17-19 . The classical cell...

SNF1Related Protein Kinase 1 SnRK1

The sucrose synthase gene that is expressed in potato tubers is SUS4 (Fu and Park 1995). Under normal conditions, it is expressed only in tubers but its expression can be induced in leaves in response to incubation with high concentrations of sucrose (Fu and Park 1995) its expression is not affected at all by glucose. Purcell et al. (1998) reported that expression of SUS4 required the activity of a regulatory protein kinase called sucrose nonfermenting-1-related protein kinase 1 (SnRK1). This protein kinase was shown subsequently to be required for the redox modulation Fig. 4.3 The relative activities of sucrose synthase and invertase in potato tubers determine how much carbon enters the storage pathway for starch biosynthesis and how much enters the glycolytic pathway. The starch biosynthesis pathway is controlled by the metabolic regulator, SnRKl (McKibbin et al. 2006) Fig. 4.3 The relative activities of sucrose synthase and invertase in potato tubers determine how much carbon...

Modifying plant physiology to take advantage of additional photosynthate

Additional genetic modifications are likely to be needed if higher yield increases are to be realized. One of the modifications that has shown promise is increasing the capacity for sucrose synthesis during the day. This shifts carbon partitioning and has allowed substantial increases in yields of tomatoes, even without increased rates of photosynthesis. Hussain et al (1999) have argued that changes in carbon partitioning brought about by changes in SPS activity may be important in adaptation of rice to increased availability of photosynthate. Similarly, Nakano et al (1997) showed that increasing nitrogen nutrition increases SPS activity. SPS activity increased by 10 to 20 by growth at 66 Pa CO,, whereas increasing leaf nitrogen content fourfold increased SPS activity by twofold. Since the cytosolic FBPase is an important regulatory step, it could be that the hexose export pathway is suppressed in normal plants and is only used when the triose phosphate export pathway is blocked. To...

General Anatomical Characteristics Of In Vitro Plants

Generally, anatomical characteristics especially the leaf anatomy of in vitro plants grown in the conventional micropropagation system has been studied intensively in the last few years. Conventionally, micropropagation is carried away using small, relatively airtight culture vessels containing nutrient media with 20-30 g L-1 sucrose (as a carbon source for the plantlets) and under a low PPF of about 30-80 mol

The Trehalose Pathway

The effect of trehalose on starch metabolism may be brought about through activation of the enzymes sucrose synthase and AGPase (Muller et al. 1998 Kolbe et al. 2005). Both are key enzymes in the starch biosynthetic pathway. These enzymes are also regulated by SnRK1, suggesting that trehalose pathway signalling interacts with the SnRK1 system. Recently, it has been shown that SnRK1 can phosphorylate and inactivate some TPS isozymes from Arabidopsis (Harthill et al. 2006), adding considerable support to this hypothesis.

Applications in Biotechnology

Free sugars are desirable in some crops, the obvious examples being sugar beet and sugar cane. The enzymes targeted by breeders and biotechnologists in this case are those that make sucrose, i.e. SPS and sucrose phosphate phosphatase (SPP), and those that break it down, i.e. sucrose synthase and invertase. Once again, a trait that has been a target for many years for food crops has received new impetus as the biofuel market has become established. Sugar cane producers, in particular, who have been shut out of the European market by import tariffs and the effect of subsidies given to Europe's sugar beet farmers, are now seeing their profit margins increasing at last, and biotechnology companies are again turning their attention to a crop in which previously it may not have been worth investing.

Pathogenesisrelated Proteins

Classes of defence stress-related identified proteins include protease inhibitors peroxidase, proteomase and carboxylase. Many unique nodule proteins have been revealed for the first time (Wienkoop and Saalbach, 2003). Some proteins are not under the influence of signalling pathways such as activation of MMP2 protein is not dependent on salicylic acid or jasmonic acid (JA) signalling pathways. Proteins not identified in the previous proteo-mic studies of nodules include halo acid dehalogenase-like family, which has a sequence similar to sucrose-6-phosphate phosphohydrolase and a sequence from Arabidopsis that has halo acid dehalogenase-like domain, osmotin-like protein precursor, UVB resistance protein-like protein, thaumatin-like protein PR-5b and MHN13. The last one (MHN13), identified in M. trancatula (Gamas et al., 1998), is closely related to the PR10 family unlike some other members of the PR10 family found in M. trancatula, such as MtPR10-1, which is constitutively expressed in...

Responses To Light Quantity

The responses of light-dominant plants are frequently of a semiquantitative nature over a wide range of irradiance and duration of light. There are, however, considerable differences between species in the way in which they respond to light. Carnation shows some response to a 2 h night-break in a 16 h dark period, but not to a 2 h extension following an 8 h photoperiod. In this species, acceleration of flowering time continues to increase with increase in the duration of light until it is given continuously throughout the 24 h cycle (Harris, 1968). Irrespective of whether light was given intermittently or continuously, the flowering response was found to be a function of the light integral. However, maximum response was obtained only when the light was continued throughout the 24 h cycle. Thus, here there seems to be evidence for a photon-counting device and also for a photoperiodic timekeeping mechanism since a 2 h exposure to light was effective only as a night-break. Flowering in...

Carbon nutrition of mycorrhizal fungi A External organic carbon sources

The very limited in vitro growth of hyphae from germinated spores of arbuscular mycorrhizal fungi may be somewhat stimulated by addition of nutrients to the medium. Although some early work indicated that sugars are inhibitory or non-stimulatory (see Hepper, 1987), it now appears that sucrose and glucose can be stimulatory at low concentrations (Siqueira et al., 1982 Carr et al., 1985 Siqueira and Hubbell, 1985). The optimum levels for stimulation of around 2 gkg ' fresh wt are similar to the concentrations of ethanol-soluble carbohydrates recorded in mycorrhizal leek roots (Amijee et al., 1990).

Carbon transfer from the host

Photosynthate is transported to the root mainly as sucrose but the form and mode of the carbon transfer from the plant to the fungus are as yet unknown. Elevated levels of invertase activity have been recorded in roots of ectomycorrhiza (Lewis and Harley, 1965) and arbuscular mycorrhiza (Dehne, 1986 Snellgrove et al., 1987), while the possible role of sucrose synthase has not been investigated. Gel electrophoresis showed that the increased invertase activity in mycorrhizal roots was due to a stimulation of the activity of host enzymes (Snellgrove et al., 1987), but otherwise it is not known whether the sucrose-hydrolysing enzymes are of plant or of fungal origin.

Low Nutritive Quality Of Douglasfir Foliage

Likewise, Douglas-fir trees resistant to budworm defoliation had higher levels of sugars in their foliage than susceptible trees at all three sites (Clancy, 2001). This is in agreement with results from artificial diet bioassays budworm fitness was best on artificial diets with sugar (i.e., sucrose) concentrations of 6 dry weight, which is near the lower limit observed for Douglas-fir foliage (Clancy, 1992b) (Fig. 3). Sucrose dry wt.) Figure 3. Estimated western spruce budworm population growth (number of first instars alive at the beginning of the F,, F , and F, generations) for artificial diets with different levels of sucrose, assuming all populations were equal at the beginning of the Pi generation (redrawn from Clancy 1992b ). See Clancy (1991b) for model of population growth used to calculate the estimates The downward arrows (I) and corresponding italic numbers on the x-axis indicate the lowest and highest concentration of sugars observed in current-year Douglas-fir foliage....

Tuber Storage Parenchyma Ultrastructure

The dormant parenchyma cells contain plastids (Gerola and Dassu, 1960 Tulett et al., 1969), mitochondria, dictyosomes (Kaeser, 1988), a nucleus, and nucleoli (Williams and Jordon, 1980). The cells have high levels of arginine, glutamine, and asparagines, very low metabolism of DNA and RNA, low amounts of polysomes, and low levels of polyamines (Favali et al, 1984). They are highly vacuolated, causing the nuclei and other organelles to be adjacent to the cell walls. The vacuoles are the storage site for fructans, and vesicles are formed in the cytoplasm, facilitating fructan synthesis from sucrose entering the cell (Kaeser, 1983). There is a close association of the plastids with mitochondria and the nucleus (Figure 4.6A) (Ishikawa and Yoshida, 1985). The nuclei display regions of condensed chromatin and contain several nucleoli (Figure 4.6C) (Jordan and Chapman, 1971). The plastids vary in structure and are found both scattered in the peripheral

Genes Involved in Bacterial Differentiation and Nodule Development

Carbon supply to the bacteroids is a strict requirement for the effective functioning of nodules. Symbiotic nitrogen fixation (SNF) depends primarily on the import of sucrose in the nodule. Sucrose synthase (SucS), cleaving sucrose in UDP-Glc and free fructoses, was shown to be essential for C supply, and plays a role in regulating the C metabolism and N fixation in nodules. Analysis in pea and M. truncatula revealed expression of the SucS gene in infected cells of the fixation zone, as well as in the meristematic region, prefixing zone, inner cortex, and nodule vasculature (Hohnjec et al. 2003). Antisense SucS1 plants of M. truncatula and the pea mutant rug4 showed less SucS activity, impaired SNF, and premature senescence (Gordon et al. 1999 Baier et al. 2007). Decreased SucS activity in nodules of rug4 mutants lowered the contents of soluble proteins in nodules and of the leghemoglobin, but did not influence the expression of nitrogenase genes. However, nitrogenase activity was...

Engineering Soluble Sugars

For several crop species, soluble sugar content is much more important than that of starch. This is either because soluble sugars such as sucrose are major reserve carbohydrates (e.g. in sugar cane and sugar beet), or, as in fruit-bearing species, because sugar is an important component of taste. An increase in sugar content in strawberry has been achieved through fruit-specific antisense repression of AGPase. Transgenic strawberry fruits showed a decrease in starch content of approximately 50 and an increase in total soluble solids of up to 37 (Park et al., 2006). In general, relatively little is known at the biochemical or genetic level about the factors that control the rate of sucrose storage in sugar beet taproots or sugar cane nodes. This reflects the intractability of both crops using genetics and the difficulties in assessing storage metabolism at the biochemical level. Factors controlling sucrose accumulation in storage tissues are photoassimilate partitioning on the whole...

Seed Biotechnology the Promise

Although the appropriateness of this application has been debated from various viewpoints, many applications of controllable gene expression system would be extremely valuable for eventual applications in seed biotechnology. An obvious example is the shrunken2 (sh2) mutation in ADP-Glc pyrophosphorylase that greatly reduces the starch content (from 65 to 25 ) and increases the sucrose

Expression profiles of CDK genes structures and functions of promoters

(McKinney and Heitz, 1991 Koch and Nasmyth, 1994 Muller, 1995 Zhu et al, 2004 Ito, 2005). Early Northern hybridization studies revealed that the accumulation of CDKB transcripts in G2 M cells is a unique, plant-specific characteristic of the non-PSTAIRE kinase genes. The other CDK genes in the families A, C, D and E display constitutive expression in synchronized cells and different plant organs (Martinez et al., 1992 Hemerly et al., 1993 Magyar et al., 1993, 1997 Segers et al., 1996 Sauter, 1997 Umeda et al., 1999 Joubes et al., 2001 Sorrell et al, 2001 Freeman et al., 2003 Esponosa-Ruiz et al., 2004). The recent genome-wide transcript profiling of the core Arabidopsis cell cycle via Affymetrix microarrays confirmed that most CDK-related kinase genes were relatively constantly expressed in synchronized cells (Menges et al., 2005). These studies refined previous data on the expression pattern of the CDKB genes, showing an early G2 peak for the CDKB1 1 2 genes and a mitotic peak for...

Shootroot distribution of carbon

Carbon-14 labelled substrates may be fed directly to the plants by foliar application (L'Annunziata, 1979). This approach was used by Schumacher and Smucker (1985) to study effects of localized anoxia on carbon partitioning in Phaseolus vulgaris L. They applied U-14C sucrose directly to abraded areas of the leaves and the uptake of 14 C was quantified by removal of the source leaf and determination of the radiolabel in and on that leaf. Obviously these foliar applications of labelled compounds have a limited potential for the study of carbon balance as the pattern of translocation of photosynthates will be different from the normal phloem loading-unloading pattern. The methods may be of some use for studying the below-ground carbon balance but they find their main use when specifically labelled carbohydrates are used for analysis of metabolic pathways.

Proteomics Of Developing Seeds

Seeds of legume species are an important protein source, with 20 to as much as 40 protein content. However, the fact that the major proteins stored in these seeds are poor in sulfur-containing amino acids and the presence of nutritionally undesirable compounds, such as protease inhibitors, remain limiting factors. To address these questions, seed development in M. truncatula was investigated at specific stages of seed filling 2 . One hundred twenty proteins differing in kinetics of appearance were subjected to MALDI-TOF-MS. These analyses allowed us to identify 84 of them, some of which had previously been shown to accumulate during seed development in legumes (e.g., legumins, vicilins, convicilins, and lipoxygenases), confirming the validity of M. truncatula as a model for analysis of legume seed filling. The study also revealed proteins presumably involved in cell division during embryogenesis (tubulin and annexin). Their abundance decreased before the accumulation of the major...

Genetic Control Of Starch Synthesis

In considering the loci known to affect starch synthesis, it is useful to discuss separately those loci that have a role in the synthesis of starch and those loci that actually participate in the synthesis of the polysaccharides. The primary source of carbon skeletons for starch synthesis is sucrose translocated to the endosperm. In maize, most of the sucrose is hydrolyzed as it enters the endosperm, where sucrose is then resynthesized (22). Chourey and Nelson (5) have detected the presence of sucrose phosphate synthase in developing maize endosperms. This enzyme is required for sucrose synthesis although sucrose synthase can synthesize sucrose in vitro, but it does not appear to do so in the maize endosperm (5). It has also been reported that the maize mutant miniature 1 seed, which has a grossly defective seed phenotype, lacks both soluble and wall-bound invertase activity (E.C. in the basal portion of the developing seed (6). The lack of invertase activity in the seed is...

Early and Late Pollen Expressed Genes

Within a gene family was monitored at the microspore (MS), bicellular (BC), tricellular (TC) and mature pollen (MP) stages. Each gene is identified by the given name when available or by the AGI number. Underlined gene name indicates those that are specifically or preferentially expressed in pollen. Black line highlights genes that have been genetically or functionally characterized. A VIC K+ channel B VIC Cyclic Nucleotide-Gated ion Channel (CNGC) C GPH Sucrose-proton symporter sucrose transporter (SUC), TC 2.A.2 D Plasma membrane P3A-type H+-ATPase, TC 3.A.3 E Calmodulin-regulated Ca2+-transporting P2B-type ATPase, TC 3.A.3 F Cu2+-transporting and Zn2+ Co2+ Cd2+ Pb2+-transporting P1B-type ATPase, TC 3.A.3

Range of solutes found in plants

As already mentioned, organic solutes are extremely diverse they make up the major metabolites found in all cells (e.g. the sugars and sugar phosphates of glycolysis, the Krebs cycle and the Calvin cycle) and secondary metabolites (which vary greatly between species and tissues), as well as hormones (e.g. indole acetic acid, abscisic acid, gibberellins and kinins), storage compounds (sugars such as sucrose in many species) and osmoprotectants (such as glycine betaine see, e.g., Chapter 13). More details of some of these groups will be found in later chapters of this book this chapter continues with a summary of how the localisation of solutes in cells can be discovered.

Metabolic Control of Seed Storage Protein Synthesis 561 Nitrogen Availability and Signalling

Fig. 5.4 Schematic overview of assimilate uptake and primary storage pathway in maturing legume seeds. Potential targets for the manipulation of metabolic pathways are highlighted by circles. Sucrose and amino acids are taken up by transporters for sucrose and amino acids (SUT, AAP). Phosphoenolcaboxylase (PEPC) supply organic acids for amino acid biosynthesis. ADP-glucose pyrophosphorylase (AGP) is a key enzyme of starch production and plastidic glucose-6-P translocator (GPT) import carbon into heterotrophic plastids. Sucrose-non-fermenting-kinase (SnRKl) and abscisic acid (ABA) are involved in the mobilization of sucrose and other aspects of seed maturation (see text for details) Sucrose Sucrose Fig. 5.4 Schematic overview of assimilate uptake and primary storage pathway in maturing legume seeds. Potential targets for the manipulation of metabolic pathways are highlighted by circles. Sucrose and amino acids are taken up by transporters for sucrose and amino acids (SUT, AAP)....

TC Genes and the Transport Function

The number of maize endosperm-specific genes has been estimated as 5500 (Lai et al. 2004), 78 of them showing clear orthologs in the rice genome. The only large-scale analysis of tissue specificity available was carried out in wheat (Drea et al. 2005) using in situ hybridization analyses 3, 6, and 9 days after anthesis (DAA) kernel sections. In this study 76 out of 665 genes examined (expression data can be viewed at were found to be expressed in the modified aleurone, and among them 32 were found to be expressed exclusively in this tissue within the kernel. The function of the majority of these genes is currently unknown and, more surprisingly, the list does not contain genes involved in transport processes. A similar result has been found in the screening efforts conducted to identify TC-specific genes in barley and maize (see below). This indicates that the morphology and transport adaptation of TC is, very likely, not determined by the expression of tissue-specific genes but by...

Products of C4 metabolism can be identified by mass spectrometry

Measuring the distribution of the 12C and the 13C isotopes in a photosyn-thetic product (e.g., sucrose) can reveal whether it has been formed by C3 or C4 metabolism. 12C and 13C occur as natural carbon isotopes in atmospheric CO2 in the ratio of 98.89 and 1.11 , respectively. Due to a kinetic isotope effect RubisCO reacts with 12CO2 more rapidly than with 13CO2. For this reason, the ratio 13C 12C is lower in the products of C3 photosynthesis than in the atmosphere. The ratio 13C 12C can be determined by mass spectrometry and is expressed as a 613C value. As a standard, one uses the distribution of the two isotopes in a defined limestone. Products of C3 photosynthesis show 613C values of 28 V. In the PEP carboxylase reaction of C4 metabolism the preference for 12C over 13C is less pronounced. As in C4 plants practically the total amount of CO2 which is prefixed by PEP carboxylase reacts further in the bundle sheath cells with RubisCO, the photosynthesis of C4 plants yields a 613C value...

Symbiotic associations

At a broader scale, such associations may result in a substantial input of fixed nitrogen to the ecosystem (see Section 2.1). The cyanobacterium benefits from the protection of the moss (either simply in the form of shelter from extreme abiotic conditions or through chemical optimization of the microenviroment by the moss) as well as from sugars leaked or potentially secreted by the host (Adams & Duggan 2008). Occasionally, green algae may occur inside the laminal cells of mosses (Reese 1981), but such endophytes certainly carry no benefits to the host. Mosses, like most other land plants, are also frequently colonized by heterotrophic prokaryotes, particularly methylobacteria, which consume methanol and other small organic molecules emitted by the host. Although the moss plant may not gain any nutrients from its epiphyte, these bacteria produce cytokinins and other phytohormones that promote the growth of the plant (Hornschuh et al. 2002). The hyalocysts of submerged Sphagnum...

CO2 fixed during the night is stored as malic acid

Nocturnal fixation of CO2 is catalyzed by phosphoenolpyruvate carboxylase, in the same way as in the metabolism of C4 plants and guard cells (Fig. 8.4). In many CAM plants the phosphoenolpyruvate required is generated from the degradation of starch, but in other plants soluble carbohydrates, such as sucrose (section 9.2) and fructanes (section 9.5), may also serve as carbon stores. Figure 8.17 shows a scheme of the CAM metabolism using starch as a carbon reservoir. The starch located in the chloroplasts is degraded to triose phosphate (section 9.1), which is then exported via the triose

Auto fluorescent proteins applied as tools for the visualization of ecological processes

And the conditions that bacteria encounter in the rhizo- and phyllosphere. For example Leveau and Lindow (2001) applied an expression system that showed that the use of sugars, e.g., fructose and or sucrose is mainly responsible for the growth of Erwinia herbicola on bean leaves. The construction and application of two bacterial sensors for the detection of nitrate availability indicated that roots compete for nitrate with the microbial rhizosphere population (DeAngelis et al. 2005). Studies on thiamine synthesis gfp reporter systems in Rhizobium leguminosarum bv. viciae showed that the rhizosphere of vetch and pea is poor in thiamine and that thiamine production is induced in the rhizosphere (Karunakaran et al. 2006). Another GFP-based study by Aldon et al. (2000) showed that physical contact between the bacterial cell and the plant strongly induces the expression of the hrp genes. The use of bioreporters has significantly contributed to the fundamental understanding of how bacteria...

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