Format: ORAL

Yao-Wu Yuan

Department of Ecology & Evolutionary Biology, University of Connecticut, USA

About one third of all angiosperm species produce flowers with petals fused into a corolla tube. Differences in the length, width, and curvature of the corolla tube have led to an endless variety of differently shaped flowers that attract specialized groups of pollinators (e.g., beeflies, hawkmoths, hummingbirds, nectar bats). As such, the corolla tube is considered a key morphological innovation that contributes to plant diversification and speciation; yet it remains one of the least understood plant organs from a developmental genetics perspective. In this talk, I will present our work towards understanding this problem using monkeyflowers (Mimulus) as a model system. Through genetic analyses of several Mimulus mutants with split corolla tubes, characterization of corolla tube ontogenesis in the wild type and mutants, and a series of transgenic experiments, we have established a regulatory pathway and a new conceptual model for the developmental genetic control of corolla tube formation. At the heart of this model is auxin-induced synchronized growth between the bases of the petal primordia and the inter-primordial regions during early stages of flower development. Upstream of this core module is the tasiRNA-ARF3/4 pathway that regulates auxin homeostasis in the synchronized growth zone; downstream is an organ boundary gene (MlNAC1) that suppresses localized tissue growth if not repressed by auxin signaling. We expect that this conceptual model and the regulatory pathway (i.e., tasiRNA-ARF3/4-auxin-MlNAC1) will serve the foundation for many interesting studies on corolla tube development and evolution in the coming years.