Response of two rice cultivars differing in their sensitivity towards arsenic, differs in their expression of glutaredoxin and glutathione S transferase genes and antioxidant usage

Embodied study investigates the role of GRX and associated antioxidant enzymes in the detoxification mechanism between arsenic (As) sensitive (Usar-3) and tolerant cultivar (Pant Dhan 11) of Oryza sativa against As(III) and As(V), under GSH enriched, and GSH deprived conditions. The overall growth and physiological parameters in sensitive cultivar were lower than the tolerant cultivar, against various treatments of As(III) and As(V). The As accumulation in sensitive cv. against both As(III) and As(V) was lower than the corresponding treatments in tolerant cv. However, the As translocation against As(V) was lower (35% and 64%, resp.) than that of As(III), in both the cultivars. In sensitive cv. translocation of Zn and Cu was influenced by both As(V) and As(III) whereas, in tolerant cv. the translocation of Cu, Mn and Zn was influenced only by As(III). Translocation of Fe was negatively influenced by translocation of As in sensitive cv. and positively in tolerant cv. Strong correlation between H₂O₂, SOD, GRX, GR, GST and GSH/GSSG in sensitive cv. and between DHAR, APX, MDHAR and AsA in tolerant cv. demonstrates the underlying preference of GSH as electron donor for detoxification of H₂O₂ in sensitive cv. and AsA in tolerant cv. Higher expression of the four GRX and two GST genes in the sensitive cv. than tolerant cv, suggests that under As stress, GRX are synthesized more in the sensitive cv. than tolerant cv. Also, the expression of four GRX genes were higher against As(V) than As(III). The higher As accumulation in the tolerant cv. is due to lower GST expression, is attributed to the absence of thiolation and sequestration of As in roots, the translocation of As to shoots is higher.