Post-Translational Regulation and Ubiquitination of Brassinosteroid Signaling Components in Plants

Brassinosteroids (BRs), a group of steroidal phytohormones, play vital roles in plant growth and stress responses. The molecular pathways underlying BR signaling have been well characterized. A growing body of data demonstrates that BR signaling components also engage in crosstalk with components from other signaling pathways to modulate plant growth, development, immune defense, and stress adaptation, and such modulation displays BR-dependent or -independent characteristics. Hence, the core components of BR signaling are of paramount importance in the regulation of multiple physiological processes during the entire plant life cycle. As an important post-translational modification, protein ubiquitination is known to precisely modulate the activity and stability of BR signaling components, as well as to govern signal output. This review centers on recent advances and provides a systematic analysis of regulatory factors influencing the stability of core BR signaling components. Particular emphasis is placed on the pivotal role of E3 ubiquitin ligases in governing the degradation, accumulation, and functional activity of these components via ubiquitination, while also contrasting the functional conservation and divergence of relevant E3s between Arabidopsis and other crops. Further dissection of the molecular regulation of BR signaling core components will facilitate a better understanding of the underlying signaling network and enable the development of strategies for crop growth regulation, yield promotion, and stress adaptation.