Expression of Glutathione Reductase 2-D (TaGR2-D) From Triticum aestivum Facilitates Arsenic Tolerance by Modulating GSH Pool and Arsenic Transporters in Transgenic Arabidopsis.

Glutathione reductase (GR) reduces oxidized glutathione (GSSG) into reduced glutathione (GSH) to facilitate redox balancing in plant cells. GSH is also converted into phytochelatins (PCs) to alleviate arsenic toxicity through vacuolar sequestration. Herein, we found a drastically reduced GSH pool during arsenic treatments in bread wheat. In contrast, TaGR2-D expression and GR activity were significantly increased, which tentatively indicated its role in arsenic stress response. Recombinant expression of TaGR2-D provided significant arsenic tolerance to yeast cells. TaGR2-D expressing transgenic Arabidopsis lines exhibited considerable tolerance against As and As treatments, with significantly higher seed germination rate, root length, and overall growth compared to wild-type (WT) plants. Additionally, they displayed higher accumulation of proline, relative water content, and photosynthetic pigments, coupled with reduced levels of malondialdehyde, hydrogen peroxide, and relative electrical conductivity. TaGR2-D expression significantly improved the activity of antioxidant enzymes and glutathione and ascorbate pools to reduce the oxidative stress caused by arsenic. Exogenous GSH supplementation reinstated seed germination rate and seedling growth of WT comparable to transgenic lines during arsenic stress, suggesting that the arsenic tolerance in TaGR2-D expressing plants could be due to increased GSH pool. Furthermore, transgenic lines showed significantly reduced arsenic accumulation with increased expression of arsenic efflux transporters (AtNIP5;1 and AtNIP6;1) during As and As treatments. Significantly increased expression of AtPCS1, AtABCC1, and AtABCC2 during arsenic treatments suggested increased PCs biosynthesis and vacuolar sequestration of PCs-As complex in transgenic lines. The study demonstrated a way to alleviate arsenic toxicity and associated oxidative stress simultaneously in plants.