Auxin efflux transporter MtPIN10 regulates compound leaf and flower development in Medicago truncatula

Plant diversity in nature is to a large extent reflected by morphological diversity of their leaves. Both simple and dissected (with multiple blades or leaflets) leaves are initiated from shoot apical meristem (SAM) in a highly ordered fashion. Similarly, development of leaflets from leaf marginal meristem (marginal blastozone) is also highly ordered. How morphological diversity of plant leaves is regulated remains an important topic of studies on plant form evolution. Here, we describe isolation and characterization of loss-of-function mutants of auxin efflux transporter MtPIN10 of a legume species, Medicago truncatula. Mtpin10 mutants exhibit defects in diverse developmental processes including leaf and leaflet development. Cross species genetic complementation demonstrates that MtPIN10 and Arabidopsis PIN1 are functional orthologs. Double mutant analyses reveal complex genetic interactions between MtPIN10 and Medicago SINGLE LEAFLET1 (SGL1) and CUP-SHAPED COTYLEDON2 (MtCUC2), three regulatory genes involved in developmental processes including dissected leaf and flower development.