Early salinity response in root of salt sensitive Olea europaea L. cv Leccino

The present study evaluates the molecular mechanisms involved, under salt stress, in the roots of Olea europaea L. cultivar Leccino (salt sensitive). We hypothesized that during the first phase of salt application the inactivation of proton pumps H+-ATPases and sodium antiporter Na+/H+ in roots determine the sodium translocation in the shoot. To verify this hypothesis, plants of olive tree (cv. Leccino) were treated with 60 mM NaCl salt and sampled after 24 h, 48 h, and seven days. Data proved that Leccino's stem accumulate Na+ after seven days of exposure. In root, the relative expressions of eight genes (five P-ATPase, one V-ATPase sub E, SOS1, and NHX) indicated that NaCl treatment led to a reduction in P-ATPase 1 and SOS1 expressions after 24 h, then NHX and V-ATPase sub E after 48 h and finally P-ATPase 8 after 7 days. The reduction of the electrochemical proton gradient due to the under-expression of P-ATPase is consistent with the accumulation of sodium in the roots and inactivation of SOS1 and the vacuolar Na+/H+ exchanger. These two genes have a clear biological role in the exclusion of sodium from the cytosol, mobilizing it outwards. In conclusion, these results provide the evidences that H+-pumping expression was decreased by salinity treatment in the early phase of root salt response in sensible olive cultivar Leccino.