Genome-Wide Identification of the SRS Gene Family in Poplar and Expression Analysis Under Drought Stress and Salt Stress

The Short Internodes-Related Sequence (SRS) family is a class of transcription factors unique to plants that are essential for controlling their growth, development, and stress responses. Nevertheless, information regarding the characterization and biological function of poplar SRS family members remains limited. In this study, we identified 10 members of the SRS gene family in the genome of Populus tremula using bioinformatics, distributed on seven chromosomes and named PtSRS01-PtSRS10 based on their locations. Our phylogenetic analysis results indicated that PtSRS genes can be categorized into five subfamilies and that members of each subfamily have similar gene structures and motifs. Collinearity analysis indicated that the expansion of the PtSRS gene family is caused by segmental duplication and is influenced by purifying selection during its evolutionary process. Cis-acting element analysis revealed that PtSRS was enriched in cis-acting elements related to growth and development, light response, hormone induction, and stress response. Quantitative real-time PCR revealed that drought and salt (NaCl) treatments affected the expression of several PtSRS genes, with PtSRS04 and PtSRS05 being the two genes with the most significant expression levels, with PtSRS04 showing a 700-fold increase in relative gene expression level after 8 d of drought stress and the PtSRS05 gene showing a 38-fold increase in gene expression level at 48 h of NaCl stress, suggesting that they could be crucial in salt and drought stress. The results presented herein provide a theoretical basis for subsequent in-depth studies on the involvement of poplar SRS gene family members in drought and salt stress resistance.