The legume NOOT-BOP-COCH-LIKE genes are conserved regulators of abscission, a major agronomical trait in cultivated crops

Abstract : Plants are able to lose organs selectively through a process called abscission. This process relies on the differentiation of specialized territories at the junction between organs and the plant body that are called abscission zones (AZ). Several genes control the formation or functioning of these AZ. We have characterized BLADE-ON-PETIOLE (BOP) orthologues from several legume plants and studied their roles in the abscission process using a mutant approach. Here, we show that the Medicago truncatula NODULE ROOT (NOOT), the Pisum sativum COCHLEATA (COCH) and their orthologue in Lotus japonicus are strictly necessary for the abscission of not only petals, but also leaflets, leaves and fruits. We also showed that the expression pattern of the M. truncatula pNOOT::GUS fusion is associated with functional and vestigial AZs when expressed in Arabidopsis. In addition, we show that the stip mutant from Lupinus angustifolius, defective in stipule formation and leaf abscission, is mutated in a BOP orthologue. In conclusion, this study shows that this clade of proteins plays an important conserved role in promoting abscission of all aerial organs studied so far.