MtFDa is essential for flowering control and inflorescence development in Medicago truncatula

Flowering plants display a vast diversity of flowering time and inflorescence architecture, which plays an important role in determining seed yield and fruit production. However, the molecular mechanism underlying the flowering control and compound inflorescence development, especially in legumes, remain to be elucidated. Here, we reported the identification of MtFDa, an essential regulator of flowering in the model legume Medicago truncatula. Mutation of MtFDa, led to the late flowering, abnormal secondary inflorescences as well as severe floral organ defects. Biochemical and molecular analyses revealed that MtFDa physically interacts with M. truncaula FLOWERING LOCUS T homolog, MtFTa1, a key regulator of Medicago flowering time, and this interaction facilitates MtFDa's function in activating the expression of MtSOC1a. Moreover, we demonstrated that MtFDa may affect secondary inflorescence development via regulating MtFULc expression in M. truncatula. Our findings help elucidate the mechanism of MtFDa-mediated regulation of flowering time and inflorescence development and provide insights into understanding the genetic regulatory network underlying complex productive development in legumes.