Genome-Wide Identification of the Medicago ruthenica FTIP Gene Family and Expression Profiling Under Salt Stresses

FT-interacting proteins (FTIPs) function in signal transduction and metabolite transport, which are important to plant growth, development, and reproduction. Their bioinformatic characteristics and functions in Medicago ruthenica, a forage crop used for ecological restoration, remain unknown. We identified 19 MrFTIPs from the M. ruthenica genome, and they were unevenly distributed across seven chromosomes. Most of them are alkaline, labile and hydrophilic, with a structure comprising irregular coils, α-helices and extended chains. Phylogenetic analysis revealed five evolutionary clades with MrFTIPs. In total, two pairs of segmental duplication events were found, indicating a major pattern for MrFTIP expansion. Overall, 16, 11, and 22 gene pairs were identified from M. truncatula, Arabidopsis thaliana, and Glycine max, respectively. The promoter regions of MrFTIPs were enriched with abiotic stress responses and light or hormone signaling. Tissue-specific analysis revealed that 7 MrFTIPs were highly expressed in leaves, 9 MrFTIPs were highly expressed in petals, and 6 MrFTIPs were highly expressed in stigma and anthers. MrFTIP17 continues to be upregulated among tissues under salt stress, and MrFTIP8 continues to be upregulated among tissues under salt–alkali stress. Collectively, our study systematically characterized the genomic features, evolutionary patterns and cis-regulatory characteristics of the MrFTIP gene family in M. ruthenica, and identified MrFTIP8 and MrFTIP17 as candidate genes associated with salt stress responses in this species, thus providing insights into and potential targets for the molecular and conventional breeding of M. ruthenica.