Glutathione Homeostasis Plays a Critical Role in Protecting Plants from Abiotic Stresses and in Heavy Metals Phytoremediation

Abstract: Glutathione (GSH) plays important roles in protecting cells from oxidative stress caused by exposure to toxic metals, xenobiotics and other abiotic stresses. The g-glutamyl cycle maintains GHS homeostasis, which involves GSH synthesis and degradation, and the recycling of the component amino acids. Overexpression of GSH biosynthesis pathway genes increases the levels of GSH, which chelates toxic metals and hence provides tolerance in the plant tissues. Previously, we developed a genetics-based As remediation strategy in Arabidopsis by tissue-specific expression of bacterial arsenate reductase, ArsC, gamma-glutamylcysteine synthase, g-ECS, genes and RNAi knockdown of an endogenous arsenate reductase AtACR2, which resulted in the efficient extraction and hyperaccumulation of As into the above ground plant tissues. We have transferred this technology to a high biomass, fast growing non-food crop- Crambe abyssinica for the application of this strategy to the As contaminated fields.

Further, we have identified a small gene family encoding γ-glutamyl cyclotransferases, GGCTs, which are involved in the g-glutamyl cycle required for maintaining GSH homeostasis via recycling Glu, a key nitrogen-storing amino acid. Manipulation of GGCT genes in Arabidopsis showed enhanced tolerance to multiple abiotic stresses and produced higher levels of Glu precursor 5-oxoproline. GGCT2;1 T-DNA mutants become severely sensitive to ABA, salt, and mannitol.

Our studies suggest that GSH homeostasis plays important roles in maintaining cellular redox for protection of plants under abiotic stresses and holds great potential for developing ‘Climate Resilient Crops” as well as developing plants for phytoremediation of toxic metals and metalloids.

Host: Frans Maathuis