Conservation and divergence of the TaSOS1 gene family in salt stress response in wheat ( Triticum aestivum L.)

Salinity is one of the most important problems that adversely affect crops growth, productivity and quality worldwide. Salt Overly Sensitive 1 (SOS1) gene family plays vital roles in plant response to salt stress. Herein, we report the identification of the SOS family in wheat and the exploration of the expression profiles of SOSs under salt stress. Complete genome sequences of T. aestivum were downloaded from Ensembl plant database. Conservation and divergence of TaSOS1 family were conducted by using phylogenetic tree, gene structure and synteny distribution analysis. Expression profiles of TaSOS1s were obtained based on transcriptome and qRT-PCR analysis. Totally, 119 TaSOS1 proteins in wheat were identified at the genome-wide level and classified into three groups. Six motifs were conserved in TaSOS1 gene family. Moreover, 25 TaSOS1 genes had three copies distributing in three sub-genomes (A, B and D). A total of 32, 28 and 29 TaSOS1 genes were located on the sub-genomes A, B and D, respectively. Moreover, there were 19, 12, 6, 7, 28, 5 and 12 genes located on the three homologous of chromosomes 1, 2, 3, 4, 5, 6 and 7, respectively. Two genes were mapped to unattributed scaffolds. The duplication events analysis indicated that tandem repeats contributed to the expansion of the SOS1 family in wheat. Collinearity analysis demonstrated that segmental duplications play an important role in the expansion of SOS1 members. Chromosome 7, 5, 3, and 2 showed collinear relationship. Tissue specific expression pattern analysis revealed that 41 TaSOS1 genes expressed in various tissues, such as root, shoot, leaf, spike and grain. Transcriptomic analysis revealed that 28 and 26 genes were up- and down-regulated under salinity stress, respectively, of which 18 genes were further confirmed by RT-qPCR. The plants with high expression level of these genes displayed higher tolerance to salinity stress, stronger root system, higher Fv/Fm value and water potential. The results could be helpful for further elucidating the molecular mechanism of TaSOS1 related to salt tolerance in wheat and provide a toolkit for improving the salinity tolerance of wheat.