Regulatory mechanisms of brassinosteroid signaling in plants

Abstract

Brassinosteroids (BRs) are steroidal hormones essential for plant growth and development. Over the past decade, genetic, molecular, and proteomic studies have established the complete BR signaling pathway and revealed important regulatory mechanisms. In Arabidopsis thaliana, BRs are perceived by receptor kinases that transduce the signal from the cell surface to the nucleus by an intracellular cascade of protein-protein interactions, involving kinases, phosphatases, 14-3-3 proteins, and nuclear transcription factors. In addition, the BR signaling is regulated by the plant endocytic machinery because the increased endosomal localization of the BR receptor enhances the signaling. As several counterparts of the BR signaling proteins of Arabidopsis are found in rice (Oryza sativa), the BR signaling is apparently conserved between monocotyledonous and dicotyledonous plants. In this chapter, we discuss the currently available data on BR signaling pathway and the latest findings on BR signaling regulatory mechanisms in plants.