XVI International Botanical Congess

Glutathione (GSH) has multiple regulatory and stress-protective functions. GSH is synthesized in two sequential reactions, catalyzed by g-glutamylcysteine synthetase (GSHI) and glutathione synthetase (GSHII). We isolated GSH1 and GSH2 cDNAs from Arabidopsis by functional complementation of GSH-deficient yeast mutants and alsoconstructed gene-disrupted yeast strains (gsh1::HIS3 and gsh2::HIS3), which will allow the overexpression of corresponding plant cDNAs for molecular analyses. The gsh1 strain shows an interesting phenotype, which could serve to isolate GSH1 from other organisms. We also studied the interactions between the dichloroacetamide-type herbicide safeners and toxic heavy metals in maize as to their effects on GSH metabolism. Our observations revealed a protective effect of these safeners against cadmium toxicity, due to overproduction of GSH, leading to a greater amount of GSH-derived phytochelatins (PCs), involved in the sequestration of heavy metals into the vacuole. Stepwise selection of Arabidopsis cells to resistancy towards buthionine sulfoximine (BSO), a specific inhibitor of GSHI, led to BSO tolerance in the selected cell lines, correlated with an increased level of GSH.