Abstract
Multiprotein bridging factor 1 (MBF1) is a transcription factor family playing crucial roles in plant development and stress responses. In this study, we analyzed MBF1 genes in Medicago truncatula and Medicago sativa under abiotic stresses, revealing evolutionary patterns and functional differences. Four MBF1 genes were identified in M. truncatula and two in M. sativa, with conserved MBF1 and HTH domains, similar exon/intron structures, and stress-related cis-elements in their promoters. Subcellular localization showed that MtMBF1a.1 is predominantly localized in the nucleus, while MtMBF1a.2, MtMBF1b, MtMBF1c, and MsMBF1a localize to both the nucleus and cytoplasm. In contrast, MsMBF1c is exclusively localized in the cytoplasm. An expression analysis revealed distinct stress responses: salt stress-induced MtMBF1b and MtMBF1c expression but repressed MsMBF1a and MsMBF1c. In contrast, PEG stress did not affect M. truncatula MBF1 genes but repressed both M. sativa MBF1 genes. These findings provide insights into MBF1-mediated stress adaptation and inform strategies for the molecular breeding of stress-tolerant alfalfa.