Study : Arabidopsis thaliana Genome sequencing
Arabidopsis thaliana Genome sequencing
Glutathione is essential for many aspects of plant biology and is associated with jasmonate signaling in stress responses. We isolated an Arabidopsis jasmonate hypersensitive mutant (jah2) with seedling root growth 100-fold more sensitive to inhibition by the hormone jasmonyl-isoleucine than wild type. Genetic mapping and whole genome sequencing determined the mutation is in intron 6 of GLUTATHIONE SYNTHETASE 2 (GSH2), encoding the enzyme that converts γ-GluCys (γ-EC) to glutathione (GSH). The level of GSH in jah2 and WT were not significantly different while the pad2-1 mutant, defective in GSH1 and having only 25% of WT GSH level, was not jasmonate hypersensitive. Growth defects for jah2, but not pad2, were also evident in plants grown to maturity and surprisingly, all phenotypes in the jah2 pad2-1 double mutant were weaker than in jah2. Quantification of γ-EC indicated these defects result from over accumulation of the GSH precursor by 17- and 3-fold in jah2 and the double mutants, respectively. γ-EC reportedly partially substitutes for loss of GSH, but growth inhibition seen here was not due to an excess of total GSH plus γ-EC because their sum in jah2 pad2-1 was 30% less than WT. Further, the jah2 phenotypes were lost in a JA biosynthesis mutant background, indicating the effect of γ-EC is mediated through jasmonate signaling, and not as a direct result of perturbed redox status. The results show that γ-EC has detrimental activities that require it be maintained at much lower levels than GSH.