Ubiquitination-Mediated Regulation of Brassinosteroid Signaling

Abstract

Brassinosteroids (BRs) are essential steroid hormones that coordinate plant growth, development and adaptation to changing environments. Although BR signaling has long been viewed primarily as a phosphorylation-dependent pathway, increasing evidence shows that ubiquitination provides an additional regulatory layer that shapes the abundance, activity, subcellular distribution and turnover of key signaling components. Ubiquitin-mediated regulation operates at multiple points in the BR pathway, including receptor homeostasis at the plasma membrane, turnover of GSK3-like kinases, and stability control of the transcription factors BES1/BZR1. These processes determine not only the strength and duration of BR signaling but also its coordination with other hormonal and stress-response pathways. In this review, we discuss recent advances in ubiquitin-mediated regulation of BR signaling, focusing on receptor-level control, proteolytic regulation of core signaling components, and modulation of transcriptional outputs. We also highlight emerging links between ubiquitination, selective autophagy, deubiquitination and BR-associated stress responses and outline key questions concerning ubiquitin chain specificity, substrate recognition and conservation of these regulatory modules in crops. Defining how ubiquitination fine-tunes BR signaling will deepen our understanding of plant steroid hormone regulation and may provide new strategies for optimizing crop architecture, productivity, and stress resilience.