Glutathione Homeostasis – A Prerequisite to Maintain Root System Architecture in Plants

Glutathione (GSH) is vital to plant life, notably for the growth of roots. GSH, a sulphur molecule made up of the three amino acids glutamate (Glu), glycine (Gly), and cysteine (Cys), is one of the most prevalent non-protein thiols in many species, including plants. GSH homeostasis is necessary to maintain tight regulation of its intracellular concentration. GSH is synthesiszed via two ATP-dependent processes that are catalysed by γ-Glu-Cys synthetase (GSH1) and GSH synthetase (GSH2), and it is mostly degraded by γ-Glutamyl transpeptidases (γ-GT), which split GSH into cysteinyl-glycine (Cys-Gly) and Glu residue. Gamma (γ) -Glutamyl Cyclo Transferases (GGCTs) catalyse the breakdown of GSH in Cys-Gly and 5-oxoproline (5-OP) under environmental stress conditions. GSH homeostasis is, thus, the result of a fast recycling mechanism, including its synthesis and degradation by the cells. GSH has myriad of functions in plants including maintenance of root system architecture (RSA). Even though the molecular connection between root growth and GSH homeostasis has not yet been fully elucidated, several findings from the study of knockout mutants indicate that GSH and GSH-dependent enzymes play a vital role in the maintenance of RSA in plants. This review is especially designed to unravel the role of GSH homeostasis in regulating RSA in higher plants.