Glyoxalase pathway and drought stress tolerance in plants

Abstract

The ubiquitously present glyoxalase pathway consists of two enzymes, Glyoxalase I and Glyoxalase II, which act in a stepwise manner and catalyze the detoxification of a highly cytotoxic metabolite methylglyoxal to d-lactate with the help of glutathione. Methylglyoxal (MG) is generated endogenously through different enzymatic and nonenzymatic reactions and is a potent glycating agent. It inhibits cell division and forms various degrees of irreversible adducts with cellular macromolecules such as nucleic acids, lipids, and proteins. MG along with reactive oxygen species (ROS) has been shown to accumulate in plant cells in response to various abiotic stresses including drought and their accumulation results in an imbalance in different cellular metabolic processes. Plants being sessile organisms have evolved various mechanisms that permit them to cope with and withstand various degrees of stress. The glyoxalase pathway is one such mechanism which acts to control excessive accumulation of MG and ROS in the system, either directly or in cooperation with other pathways involved in stress response. In response to drought, transcript and protein levels of glyoxalases are altered which is suggestive of their involvement in stress response. MG has also been shown to induce stress-responsive signaling cascades related to drought and even regulates stomatal movements. Here, we discuss the role of the plant glyoxalase pathway with respect to drought stress adaptation.