Unifoliata-Afila interactions in pea leaf morphogenesis

Premise of the study: Processes of leaf morphogenesis provide the basis for the great diversity of leaf form among higher plants. The common garden pea (Pisum sativum) offers a developmental model system for understanding how gene and hormone interactions impart a large array of mutant leaf phenotypes. Methods: To understand the role of auxin in AF and UNI gene function and their interaction, we compared the range of leaf phenotypes on afila (af) and unifoliata (uni) double mutants, examined the effects of these mutations on auxin levels, auxin transport, auxin response via DR5::GUS, and expression of auxin-regulated genes. Key results: The adult leaves of af uni double mutants have leaflets and tendrils and typically possess two lateral pinna pairs and a terminal leaflet. The af mutants have higher auxin content, stronger auxin response, and higher expression of auxin responsive genes than wildtype. The uni mutant has reduced auxin content and transport, whereas the uni-tac mutant has higher auxin content and transport and reduced auxin response compared to wildtype. Conclusions: Auxin concentration and response differences characterize the antagonistic relationship between AF and UNI in pea leaf development. The mechanism involves modulation of auxin mediated by one or both genes; UNI is expressed in and promotes high auxin levels, and AF suppresses auxin levels.