A comprehensive study of the proteins involved in salinity stress response in roots and shoots of the FL478 genotype of rice (Oryza sativa L. ssp. indica)

Abstract

Rice, a major staple, is the most salt-sensitive cereal. High salinity triggers several adaptive responses in rice to cope with osmotic and ionic stress at the physiological, cellular and molecular levels. A major QTL for salinity tolerance, named Saltol, is present on chromosome 1 of Indian landrace varieties such as Pokkali and Nona Bokra. In this study, we characterized the early proteomic and physiological responses to salinity in roots and shoots of FL478, an inbred rice line harboring the Saltol QTL. Plantlets were cultured in hydroponic cultures with 100 mM NaCl and evaluated at 6, 24 and 48 h. At the physiological level, root length significantly increased at 48 h, whereas shoot length was reduced. Moreover, the Na+/K+ ratio was maintained at lower levels in shoots compared to roots, suggesting that roots have a protective role. More than 2000 proteins were detected in both tissues. Roots showed a faster and more coordinated proteomic response than shoots, evident after only 6 h of treatment. These responses were markedly related with transcription- and translation-related proteins. Maintenance of the mitochondrial activity and the amino acids metabolisms in roots, and activation of stress-related proteins such ash dehydrins and PLAT in shoots may play a key role during the response of the plant to salinity stress. Finally, proteomic and physiological responses showed that roots respond in a highly adaptive manner to salinity stress compared to shoots, which suggests that this tissue is critical to the tolerance observed in varieties harbouring the Saltol region.