Genome-Wide Identification and Expression Analysis of the SRS Gene Family in Medicago sativa .

SHI-related sequence ( SRS) transcription factors, specific to plants, act as crucial regulators of plant organ growth and development. Here, we examined the Medicago sativa (alfalfa) SRS gene family ( MsSRS s) to analyze the structure and function of MsSRS s using bioinformatics methods, and verify their abiotic stress responses through growth experiments. Twenty-seven MsSRS genes were identified from the genome-wide data of nontransgenic alfalfa. MsSRS s were distributed on 16 chromosomes and classified into seven different subfamilies by phylogenetic analysis. Forty-five cis -regulatory elements related to stress and phytohormone responsiveness, and tissue-specific expression occurred in the promoter sequences of MsSRSs . Ks values and Ka/Ks ratios of duplicate gene pairs showed that purifying selection affected most duplicate genes during their evolutionary history, while rapid recent positive selection strongly influenced MsSRS25 and MsSRS01 . Real-time fluorescence quantitative PCR results showed that MsSRS genes could be induced by cold and salt stress. Within 12 h of salt stress exposure, the expression levels of seven and nine MsSRSs showed significant upregulation and downregulation, respectively. Within 12 h of cold stress exposure, the expression levels of the 3 and 13 selected MsSRSs showed significant upregulation and downregulation, respectively. Thus, this study provides novel comprehensive information on the MsSRS gene family, helpful for the study of SRS-mediated tolerance in alfalfa and the functional characteristics of SRS genes in other plants.