Redox homeostasis, antioxidant defense, and methylglyoxal detoxification as markers for salt tolerance in Pokkali rice
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To identify biochemical markers for salt tolerance, two contrasting cultivars of rice (Oryza sativa L.) differing in salt tolerance were analyzed for various parameters. Pokkali, a salt-tolerant cultivar, showed considerably lower level of H2O2 as compared to IR64, a sensitive cultivar, and such a physiology may be ascribed to the higher activity of enzymes in Pokkali, which either directly or indirectly are involved in the detoxification of H2O2. Enzyme activities and the isoenzyme pattern of antioxidant enzymes also showed higher activity of different types and forms in Pokkali as compared to IR64, suggesting that Pokkali possesses a more efficient antioxidant defense system to cope up with salt-induced oxidative stress. Further, Pokkali exhibited a higher GSH/GSSG ratio along with a higher ratio of reduced ascorbate/oxidized ascorbate as compared to IR64 under NaCl stress. In addition, the activity of methylglyoxal detoxification system (glyoxalase I and II) was significantly higher in Pokkali as compared to IR64. As reduced glutathione is involved in the ascorbate–glutathione pathway as well as in the methylglyoxal detoxification pathway, it may be a point of interaction between these two. Our results suggest that both ascorbate and glutathione homeostasis, modulated also via glyoxalase enzymes, can be considered as biomarkers for salt tolerance in Pokkali rice. In addition, status of reactive oxygen species and oxidative DNA damage can serve as a quick and sensitive biomarker for screening against salt and other abiotic stresses in crop plants.
KeywordsAntioxidative defense ROS Methylglyoxal Rice Salt stress
H.E.-S. is thankful to ICGEB for pre-doctoral fellowship and B.K. is grateful for salary support from a Young Scientist grant from the Department of Science and Technology, Government of India. The research was partly supported by a grant from the Department of Biotechnology, Government of India, and the internal grants from ICGEB.
Conflict of interest
The authors declare that they have no conflict of interest. There is no financial or other relationship that might be perceived as leading to a conflict of interest.
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