Auxin response factors (ARFs) are key mediators of auxin responses,of which ARF5/MONOPTEROS(MP) plays a role in the regulation of many growth and development processes in Arabidopsis.In this article,we review recent progress in studying the regulatory functions of ARF5/MP,with a particular emphasis on its roles in mediating auxin signaling in hypophysis specification,vascular development and shoot apical meristem maintenance,as well as the structural and functional conservation of ARFs,thus provide a valuable reference for studying the molecular mechanisms of auxin signaling in plants.