The possible involvement of MYB, WAK and RIM2 proteins in salt tolerance in rice

Salinity in plants has two major components: osmotic effects (phase 1) and ionic effects (phase 2). In this research the effects of phase 1 on gene expression in two rice varieties differing in salt tolerance (IR4630 and IR15324) was studied using a modified cDNA-amplified fragment length polymorphism (AFLP) technique. To separate osmotic from ionic effects of salt, mannitol was applied as a non-ionic osmoticum at the equivalent osmotic potential to 50 mM NaCl. mRNA was sampled at 0.5, 6, 24, 48 and 192 hours after salinisation. Several products (AFLP-bands) were detected, which were upregulated in the response to ionic effects of salt in the tolerant line (IR4630) and not expressed in the sensitive line (IR15324) at both phase 1 and 2 of salinisation. Bioinformatic analysis indicated these AFLP-bands to be: 1) a gene (OsMYB) encoding a Myb-related protein (for an isolated AFLP-band belonged to salt-stressed shoots of IR4630 at 0.5 h after salinisation); 2) a gene (OsWAK) encoding a putative wall-associated protein kinase (for an isolated AFLP-band belonged to salt-stressed shoots of IR4630 at 24 h after salinisation) and 3) a gene (OsRim2) encoding a Rim 2 protein (for an isolated AFLP-band belonged to salt-stressed shoots of IR4630 at 192 h after salinisation). The possible roles of the products of candidate genes are discussed.