Genome-wide identification and expression profiling of Early 2 Factor gene family in alfalfa (Medicago sativa) reveal their response to pollen viability

Pollen viability is an important factor influencing the seed-setting rate of angiosperms. The Early 2 Factor (E2F) family of transcription factors is a central regulator of the cell cycle, playing a critical role in processes such as cell division, DNA damage repair, and cell size control. However, the mechanisms of E2F transcription factors on pollen viability in plants have been rarely reported. In this study, we identified five MsE2F genes in the genome of alfalfa ( Medicago sativa ), classified into three groups (E2F, DEL, and DP) with uneven distribution across four chromosomes. The promoter regions of MsE2F genes contained numerous cis -regulatory elements associated with plant growth, hormone signaling, and stress responses. Furthermore, MsE2F genes were found to be differentially regulated during pollen tube elongation, indicating that members of the MsE2F gene family might play critical roles in pollen viability. The structural features of MsE2F5 that were different from the other four MsE2F proteins suggested that it might have unique functions. Meanwhile, MsE2F5 presented a strong correlation with Actin Binding Proteins (ABPs) related to pollen tube elongation. Yeast one-hybrid assays demonstrated that MsE2F5 regulated the expression of key ABPs in pollen tube elongation, including MsFORMIN , MsADF , MsPROFILIN , and MsFIMBRIN , by binding to their promoter regions. Our findings offer new insights into the role of the E2F gene family in plant reproductive development. • The MsE2F gene family of alfalfa ( Medicago sativa ) was identified and analyzed in the genome. • E2F genes are involved in the elongation of the pollen tube in alfalfa. • E2F genes promote pollen tube elongation by interacting with actin-binding proteins.