Usually Multiple Amino acids Move In and Out Transporters (UMAMITs), belonging to the MtN21/EamA-like/UMAMIT superfamily, play vital roles in amino acid transport, nodule formation, and nitrogen fixation in legumes. Despite extensive studies in other species, the UMAMIT gene family remains uncharacterized at the genome-wide level in alfalfa (Medicago sativa). This study aimed to comprehensively identify and analyze the UMAMIT gene family in M. sativa and investigate the functions of the Arabidopsis umamits mutant under salt and drought stress. In this study, 46 MsUMAMIT genes were identified in the genome of alfalfa (“Zhongmu No.1”). These genes were distributed across 8 chromosomes, with protein sequence lengths ranging from 126 to 948 amino acids. Phylogenetic analyses classified the MsUMAMIT family into four groups. Collinearity analysis revealed that 17% (8 out of 46) of the genes formed segmental duplications and 24% (11 out of 46) formed tandem duplications, with all duplicated gene pairs undergoing purifying selection. Cis-acting promoter elements were involved in plant growth and development, as well as hormone and stress responses. RT-qPCR analysis indicated that MsUMAMIT44 is responsive to salt, drought, and hormone treatments (ABA, IAA). Functional validation in the Arabidopsis umamits mutant confirmed its involvement in drought tolerance, as mutant plants exhibited growth inhibition and altered expression of stress-responsive genes. This study provides the first comprehensive characterization of the UMAMIT gene family in alfalfa and establishes a functional link between UMAMIT transporters and abiotic stress responses, offering valuable targets for improving legume stress resilience.
Dai et al. (Wed,) studied this question.