Gamma-Glutamyl Cycle in Plants: Possible Implications in Apoplastic Redox Control and Redox Sensing

Conference paper
Part of the Proceedings of the International Plant Sulfur Workshop book series (PIPSW, volume 1)

Abstract

There is now increasing evidence of a gamma-glutamyl cycle occurring in plants that closely resembles what happens in animals, which consists of glutathione extrusion to the extracellular space, sequential degradation to its constituent amino acids by gamma-glutamyl transferase (GGT) and Cys-Gly dipeptidase (CD) activity, reuptake by amino acid transporters and glutathione reassembly inside the cell. Here we demonstrate that the GGT bound to the cell wall in Arabidopsis leaves recovers extracellular glutathione that is probably extruded to counteract conditions of oxidative stress due to UV-B exposure. Experiments on barley roots provide evidence of the existence of two different Cys-Gly dipeptidases: one is associated with the cell wall and has a higher affinity for reduced Cys-Gly; the other is presumably bound to the plasma membrane. The different site of CD isoforms with a different specificity for the reduced and oxidized substrate forms implies that reduced glutathione and Cys-Gly must spread through the apoplastic space before they are cleaved by the corresponding enzyme; in so doing, these thiols scan the extracellular space and eventually react with oxidants or sensitive components bound to the plasma membrane acting as sulfur switches. Taken together, these findings suggest that the gamma-glutamyl cycle is implicated in apoplastic redox control and redox sensing.

Keywords

Oxidative Stress Condition Barley Root Constituent Amino Acid Apoplastic Space Purify Plasma Membrane 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

References

  1. Destro T, Prasad D, Martignago D, Lliso Bernet I, Trentin AR, Renu IK, Ferretti M, Masi A (2011) Compensatory expression and substrate inducibility of γ-glutamyl transferase GGT2 isoform in Arabidopsis thaliana. J Exp Bot 62:805–814PubMedCrossRefGoogle Scholar
  2. Ferretti M, Destro T, Tosatto SCE, La Rocca N, Rascio N, Masi A (2009) Gamma-glutamyl transferase in the cell wall participates in extracellular glutathione salvage from the root apoplast. New Phytol 181:115–126PubMedCrossRefGoogle Scholar
  3. Grzam A, Martin MN, Hell R, Meyer AJ (2007) γ-Glutamyl transpeptidase GGT4 initiates vacuolar degradation of glutathione S-conjugates in Arabidopsis. FEBS Lett 581:3131–3138PubMedCrossRefGoogle Scholar
  4. Lohaus G, Pennewiss K, Sattelmacher B, Hussmann M, Muehling KH (2001) Is the infiltration-centrifugation technique appropriate for the isolation of apoplastic fluid? A critical evaluation with different plant species. Physiol Plant 111:457–465PubMedCrossRefGoogle Scholar
  5. Martin MN, Saladores PH, Lambert E, Hudson AO, Leustek T (2007) Localization of members of the γ-glutamyl transpeptidase family identifies sites of glutathione and glutathione S-conjugate hydrolysis. Plant Physiol 144:1715–1732PubMedCrossRefGoogle Scholar
  6. Masi A, Ghisi R, Ferretti M (2002) Measuring low-molecular-weight thiols by detecting the fluorescence of their SBD derivatives: application to studies of diurnal and UV-B induced changes in Zea mays L. J Plant Physiol 159:499–507CrossRefGoogle Scholar
  7. Meister A, Tate SS (1976) Glutathione and related gamma-glutamyl compounds: biosynthesis and utilization. Annu Rev Biochem 45:559–604PubMedCrossRefGoogle Scholar
  8. Murphy TM (1983) Membranes as targets of ultraviolet radiation. Physiol Plant 58:381–388CrossRefGoogle Scholar
  9. Ohkama-Ohtsu N, Radwan S, Peterson A, Zhao P, Badr AF, Xiang C, Oliver DJ (2007) Characterization of the extracellular γ-glutamyl transpeptidases, GGT1 and GGT2, in Arabidopsis. Plant J 49:865–877PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2012

Authors and Affiliations

  1. 1.Department of Agricultural BiotechnologyUniversity of PaduaLegnaro, PaduaItaly

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