Augmenting Salt Tolerance in Rice by Regulating Uptake and Tissue Specific Accumulation of Na - Through Ca -induced Alteration of Biochemical Events

The protective effect of Ca against NaCl toxicity was investigated in two rice varieties with contrasting for salt tolerance to understand the mechanistic details of the antagonism to address adverse effects of salinity on agriculture. The study primarily examined the influence of Ca on expression/activity of the effectors and regulators involved in Na translocation. Calcium reduced uptake of Na concomitant with higher tissue K /Na in seedlings, comparatively more in salt-tolerant Nona Bokra than in salt-sensitive IR-64, together with a significant increase in root PM H ATPase in the former, but not in the latter. Increased antagonism in Nona Bokra could be the result of Ca signalling-mediated phosphorylation of PM H ATPase in roots caused by a significant Ca -dependent increase in expression of OsCIPK24, which did not occur in IR-64. Furthermore, significant Ca -mediated NaCl-induced increase in transcription of 14-3-3 protein in Nona Bokra, but not in IR-64, might also lead to a greater protective effect of Ca in the former, as 14-3-3 protein is essential for activating PM H ATPase. Thus, efficient functioning of PM H ATPase could be key in determining resistance of plants to salinity, implying that identification of the Ca -dependent kinase phosphorylating the PM H ATPase threonine residue and manipulation of its expression, together with expression of 14-3-3 proteins could be an important strategy to improve salt tolerance of crops and their cultivation in salt-affected lands.