Crucial Roles of Brassinosteroids in Cell Wall Composition and Structure Across Species: New Insights and Biotechnological Applications.

Brassinosteroids (BR) are small endogenous phytohormones that are key regulators of plant growth, development, and stress resistance. They fulfil this role partially by modulating cell wall structure and composition through the control of genes involved in primary and secondary cell wall biosynthesis and metabolism. This affects the deposition of cellulose, lignin, and other components, and modifies the inner architecture of the wall, allowing it to adapt to the developmental status and environmental conditions. Here, we review the role of BR in cell wall modifications, highlighting recently described functions of BR in model plants in development and growth, such as cell layers interaction to regulate coordinated growth and tissue development for organ shape, skotomorphogenesis, and regulation of gravitropism for the orientation of plant growth direction against gravity. We also discuss the potential use of BR in crops to address current problems such as the need to maintain crop yield, quality, and wood production while increasing stress resistance. Among these approaches are the modification of BR biosynthesis and upregulated BR signalling, leading to increased crop development or wood deposition. We will also highlight how the use of exogenous BR applications can promote BR-related responses to improve plant fitness and productivity.