Multiple Roles of Brassinosteroid Signaling in Vascular Development.

This article focuses on the roles of brassinosteroids (BRs), a class of plant steroid hormones, in regulating vascular development in plants, particularly in the model species Arabidopsis thaliana and other plants. BRs influence both primary vascular development, affecting vascular cell division and protophloem differentiation, and secondary vascular development, where they promote xylem cell differentiation and regulate vascular stem cell maintenance through complex signaling networks involving BR receptors and transcription factors such as BES1/BZR1. The review also highlights BR crosstalk with other hormonal pathways, including the TDIF peptide signaling, and discusses conserved BR functions in secondary vascular growth across herbaceous and woody species like tomato and poplar. Despite advances, mechanisms underlying BR’s non-cell-autonomous effects and precise promotion of xylem differentiation remain areas for further research.