Quantitative expression analysis of TaSOS1 and TaSOS4 genes in cultivated and wild wheat plants under salt stress.

Salt stress is a mixture of ionic, osmotic, and oxidative stresses. The expression of TaSOS1 (a transmembrane Na(+)/H(+) antiporter) and TaSOS4 [a cytoplasmic pyridoxal (PL) kinase] genes were measured in four different salinity levels and different time courses of salinity exposure using qRT-PCR technique. Mahuti (salt tolerant) and Alamut (salt sensitive) cultivars were used as cultivated wheat, and T. boeticum and Aegilops crassa as wild wheat plants. Salt-induced expression of TaSOS1 in these wild wheat plants indicates the presence of active TaSOS1 gene on the genomes A and D. The TaSOS1 and TaSOS4 transcript levels were found to be downregulated after salt treatment in all cultivars except in A. crassa, which was in contrast with its expression pattern in roots that was being upregulated from a very low-basal expression, after salt treatments. Duncan's Multiple Range Test showed a significant difference between expression in the 200-mM NaCl concentration with the 50 and 100 mM for the TaSOS1 gene, and no significant difference for TaSOS4. Lack of significant correlation between the TaSOS1 and TaSOS4 gene expressions confirms the theory that PLP has no significant effect on the expression of the TaSOS1 gene in wheat leaves.