Diversification of three genes and their roles in sodium exclusion in bread wheat ( L.).

The ability to exclude sodium from the shoot is a crucial feature of salinity tolerance in bread wheat ( L.). The plasma membrane sodium/proton exchanger salt-overly-sensitive 1 (SOS1) is a critical Na. efflux protein in plants. Here, we cloned three homologues of the gene in bread wheat, designated , and , respectively, according to the location on group 3 chromosomes 3A, 3B and 3D. Sequence analysis demonstrated that the deduced protein-contained domains similar to the SOS1 protein, including 12 membrane-spanning regions, a long hydrophilic tail in the C-terminus, the cyclic nucleotidebinding domain, the putative auto-inhibitory domain and the phosphorylation motif. Phylogenetic analysis established the evolutionary relationships between the different copies of this gene in bread wheat and its diploid progenitors, as well as with SOS1 genes from , rice and . Analysis of transient TaSOS1-A1::green fluorescent protein expression demonstrated that TaSOS1 was exclusively localized to the plasma membrane. The yeast and Arabidopsis complementary test supported the sodium extrusion function of . Virus-induced gene silencing technology was used to further examine the function of in bread wheat.