Glyoxalase System: A Glutathione-Dependent Pathway for Abiotic Stress Tolerance in Plants

Abstract

Due to their sessile nature, plants have to go through various adverse environmental conditions. Abiotic stresses, such as salinity, drought, flooding, cold, heat, etc. have been the major environmental factors contributing to the decreased yield of important crop plants. Abiotic stress leads to an abrupt increase in the contents of methylglyoxal (MG) in plants. MG is a potent cytotoxin, and readily reacts with major macromolecules of the cell to form advanced glycation end-products (AGEs ). MG detoxification is principally carried out by the glyoxalase (GLY) system, which consists of two enzymes, GLYI and GLYII. GLYI acts upon the non-enzymatically formed complex of MG and a molecule of reduced glutathione (GSH), leading to the production of S-D-lactoylglutathione (SLG). GLYII, then, catalyzes the conversion of SLG to D-lactate giving GSH back to the system, thereby maintaining GSH homeostasis. The glyoxalase pathway keeps a check on the elevation of the MG level and helps in maintaining a higher “reduced to oxidized” GSH ratio. The glyoxalase pathway has been directly correlated to abiotic stress tolerance. Overexpression of GLY enzymes confers improved abiotic stress tolerance in plants. This chapter provides insights into the importance of the glyoxalase pathway in stress response and sheds light on the dependence of the glyoxalase pathway on GSH as the key player in regulating the pathway.