Genome-Wide Identification, Phylogenetic and Expression Analysis of Expansin Gene Family in L.

Expansins, a class of cell-wall-loosening proteins that regulate plant growth and stress resistance, have been studied in a variety of plant species. However, little is known about the present in alfalfa ( L.) due to the complexity of its tetraploidy. Based on the alfalfa (cultivar "XinjiangDaye") reference genome, we identified 168 members (). Phylogenetic analysis showed that MsEXPs consist of four subfamilies: MsEXPAs (123), MsEXPBs (25), MsEXLAs (2), and MsEXLBs (18). MsEXPAs, which account for 73.2% of MsEXPs, and are divided into twelve groups (EXPA-I-EXPA-XII). Of these, EXPA-XI members are specific to and alfalfa. Gene composition analysis revealed that the members of each individual subfamily shared a similar structure. Interestingly, about 56.3% of the -acting elements were predicted to be associated with abiotic stress, and the majority were MYB- and MYC-binding motifs, accounting for 33.9% and 36.0%, respectively. Our short-term treatment (≤24 h) with NaCl (200 mM) or PEG (polyethylene glycol, 15%) showed that the transcriptional levels of 12 in seedlings were significantly altered at the tested time point(s), indicating that are osmotic-responsive. These findings imply the potential functions of in alfalfa adaptation to high salinity and/or drought. Future studies on expression profiles under long-term (>24 h) stress treatment would provide valuable information on their involvement in the response of alfalfa to abiotic stress.