GLUTATHIONE METABOLIC GENES COORDINATELY RESPOND TO HEAVY-METALS AND JASMONIC ACID IN ARABIDOPSIS

Glutathione plays a pivotal role in protecting plants from environment al stresses, oxidative stress, xenobiotics, and some heavy metals. Ara bidopsis plants treated with cadmium or copper responded by increasing transcription of the genes for glutathione synthesis, gamma-glutamylc ysteine synthetase and glutathione synthetase, as well as glutathione reductase. The response was specific for those metals whose toxicity i s thought to be mitigated through phytochelatins, and other toxic and nontoxic metals did not alter mRNA levels. Feeding experiments suggest ed that neither oxidative stress, as results from exposure to H2O2, no r oxidized or reduced glutathione levels were responsible for activati ng transcription of these genes. Jasmonic acid also activated the same suite of genes, which suggests that it might be involved in the signa l transduction pathway for copper and cadmium. Jasmonic acid treatment increased mRNA levels and the capacity for glutathione synthesis but did not alter the glutathione content in unstressed plants, which supp orts the idea that the glutathione concentration is controlled at mult iple levels.