Cysteine, γ-Glutamylcysteine, and Glutathione Levels in Maize Seedlings

Rauser, Wilfried E.; Schupp, Robert; Rennenberg, Heinz

doi:10.1104/pp.97.1.128

Cited by 77 publications

(34 citation statements)

References 17 publications

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“…Phytochelatin synthase or yEC2 dipeptidyl transpeptidase forms the peptide chain by the addition of ,yEC moieties from GSH to an acceptor GSH molecule. Consistent with this, the GSH content decreases, at least initially, because of Cd treatment in cell cultures (3, 23), roots (19,21,28), and both roots and shoots (17).…”

supporting

confidence: 59%

“…Furthermore, the results indicate that, with Cd, the GSH synthetase reaction is the rate-limiting step of GSH synthesis, probably due to a higher sensitivity of GSH synthetase than yEC synthetase to Cd as reported for the partially purified enzymes from Petrosilenum crispum (19 99,1992 …”

Section: Discussionmentioning

confidence: 66%

“…In roots, this increase can be explained by the higher level of yEC synthetase activity and the higher contents of Cys, which may increase the rate of yEC formation (9). Additionally, the lower (19).…”

Section: Discussionmentioning

confidence: 99%

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Effect of Cadmium on γ-Glutamylcysteine Synthesis in Maize Seedlings

Rüegsegger¹,

Brunold²

1992

Plant Physiol.

205

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Cysteine, 'y-glutamylcysteine, and glutathione and the extractable activity of the enzymes of glutathione biosynthesis, 'y-glutamylcysteine synthetase (EC 6.3.2.2) and glutathione synthetase (EC 6.3.2.3), were measured in roots and leaves of maize seedlings (Zea mays L. cv LG 9) exposed to CdCI2 concentrations up to 200 micromolar. At 50 micromolar Cd2 , -y-glutamylcysteine contents increased continuously during 4 days up to 21-fold and eightfold of the control in roots and leaves, respectively. Even at

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supporting

confidence: 59%

Section: Discussionmentioning

confidence: 66%

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Effect of Cadmium on γ-Glutamylcysteine Synthesis in Maize Seedlings

Rüegsegger¹,

Brunold²

1992

Plant Physiol.

205

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“…Cd-caused accumulation of ␥-EC has also been observed in maize seedlings (Rauser et al, 1991). The fact that ␥-EC levels were so high, even in the ␥-ECS seedlings, suggests that GSH production in the Cd-treated plants was limited by GS.…”

Section: Discussionmentioning

confidence: 77%

Cadmium Tolerance and Accumulation in Indian Mustard Is Enhanced by Overexpressing γ-Glutamylcysteine Synthetase

et al. 1999

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To investigate rate-limiting factors for glutathione and phytochelatin (PC) production and the importance of these compounds for heavy metal tolerance, Indian mustard (Brassica juncea) was genetically engineered to overexpress the Escherichia coli gshI gene encoding ␥-glutamylcysteine synthetase (␥-ECS), targeted to the plastids. The ␥-ECS transgenic seedlings showed increased tolerance to Cd and had higher concentrations of PCs, ␥-GluCys, glutathione, and total non-protein thiols compared with wild-type (WT) seedlings. When tested in a hydroponic system, ␥-ECS mature plants accumulated more Cd than WT plants: shoot Cd concentrations were 40% to 90% higher. In spite of their higher tissue Cd concentration, the ␥-ECS plants grew better in the presence of Cd than WT. We conclude that overexpression of ␥-ECS increases biosynthesis of glutathione and PCs, which in turn enhances Cd tolerance and accumulation. Thus, overexpression of ␥-ECS appears to be a promising strategy for the production of plants with superior heavy metal phytoremediation capacity.Heavy metals and metalloids such as Cd, Pb, Hg, As, and Se are an increasing environmental problem worldwide. Plants can be used to remove heavy metals by accumulating, stabilizing, or biochemically transforming them. This cost-effective and environment-friendly technology has been called "phytoremediation" (Salt et al., 1995). Hyperaccumulators-plant species that accumulate extremely high concentrations of heavy metals in shoots-offer one option for the phytoremediation of metal-contaminated sites. However, hyperaccumulators tend to grow slower and produce little biomass (Brooks, 1994). An alternative approach is to genetically engineer fast-growing species to improve their metal tolerance and metal-accumulating capacity. A suitable target species for this strategy is Indian mustard (Brassica juncea), which has a large biomass production, a relatively high trace element accumulation capacity (Dushenkov et al., 1995), and can be genetically engineered .Non-protein thiols (NPTs), which contain a high percentage of Cys sulfhydryl residues in plants, play a pivotal role in heavy metal detoxification. The reduced form of glutathione (␥-Glu-Cys-Gly, GSH) is one of the most important components of NPT metabolism. GSH may play several roles in heavy metal tolerance and sequestration. It protects cells from oxidative stress damage, such as that caused by heavy metals in plants (Gallego et al

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“…In fact, the above-described behavior is consistent with the induction of GSH-consuming activities such as PC biosynthesis (Zenk, 1996), but does not exclude a direct effect of Cd on enzyme activities involved in GSH synthesis, i.e. GS (Rauser et al, 1991;Schneider and Bergmann, 1995). Moreover, under Cd stress the regulation of GSH biosynthesis undergoes deep changes, mainly at transcriptional level, as indicated by the increase of the g-EC synthetase and GS mRNA relative abundances, probably caused by the transient GSH depletion itself (Schäfer et al, 1998;Xiang and Oliver, 1998).…”

Section: Discussionmentioning

confidence: 87%

Heavy Metal Stress and Sulfate Uptake in Maize Roots

et al. 2006

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ZmST1;1, a putative high-affinity sulfate transporter gene expressed in maize (Zea mays) roots, was functionally characterized and its expression patterns were analyzed in roots of plants exposed to different heavy metals (Cd, Zn, and Cu) interfering with thiol metabolism. The ZmST1;1 cDNA was expressed in the yeast (Saccharomyces cerevisiae) sulfate transporter mutant CP154-7A. Kinetic analysis of sulfate uptake isotherm, determined on complemented yeast cells, revealed that ZmST1;1 has a high affinity for sulfate (K m value of 14.6 6 0.4 mM). Cd, Zn, and Cu exposure increased both ZmST1;1 expression and root sulfate uptake capacity. The metal-induced sulfate uptakes were accompanied by deep alterations in both thiol metabolism and levels of compounds such as reduced glutathione (GSH), probably involved as signals in sulfate uptake modulation. Cd and Zn exposure strongly increased the level of nonprotein thiols of the roots, indicating the induction of additional sinks for reduced sulfur, but differently affected root GSH contents that decreased or increased following Cd or Zn stress, respectively. Moreover, during Cd stress a clear relation between the ZmST1;1 mRNA abundance increment and the entity of the GSH decrement was impossible to evince. Conversely, Cu stress did not affect nonprotein thiol levels, but resulted in a deep contraction of GSH pools. Our data suggest that during heavy metal stress sulfate uptake by roots may be controlled by both GSH-dependent or -independent signaling pathways. Finally, some evidence suggesting that root sulfate availability in Cd-stressed plants may limit GSH biosynthesis and thus Cd tolerance are discussed.To minimize the detrimental effects of heavy metal accumulation, plants have evolved detoxification mechanisms, mainly based on chelation and subcellular compartmentalization (Clemens, 2001). The efficiency of these processes might result in the natural heavy metals tolerance and their basic understanding might be crucial for improving plant performances in phytoextraction of heavy metals from polluted soils (Salt et al., 1998;Pilon-Smits, 2005).Chelation of heavy metals is a ubiquitous detoxification strategy described in a wide variety of plants (Zenk, 1996;Clemens, 2001). One of the principal classes of heavy metal chelators known in plants is phytochelatins (PCs), a family of Cys-rich peptides with the general structure (g-Glu-Cys) n -Gly (n 5 2-11). PCs are synthesized nontranslationally from reduced glutathione (GSH) in a transpeptidation reaction catalyzed by the enzyme PC synthase (PCS; Rea et al., 2004). Their synthesis is induced within minutes following exposure to different metals or metalloids; among these, Cd is the strongest inducer, whereas other metals such as Cu, Zn, Pb, and Ni are less effective and require higher external levels for induction (Grill et al., 1987;Maitani et al., 1996). Interestingly, some inducers, such as Zn, do not seem to serve as substrates for chelation (Clemens, 2001;Souza and Rauser, 2003).The mechanism of heavy metal detoxif...

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Cysteine, γ-Glutamylcysteine, and Glutathione Levels in Maize Seedlings

Cited by 77 publications

References 17 publications

Effect of Cadmium on γ-Glutamylcysteine Synthesis in Maize Seedlings

Effect of Cadmium on γ-Glutamylcysteine Synthesis in Maize Seedlings

Cadmium Tolerance and Accumulation in Indian Mustard Is Enhanced by Overexpressing γ-Glutamylcysteine Synthetase

Heavy Metal Stress and Sulfate Uptake in Maize Roots

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