Brassinosteroids (BRs) are specific phytosteroids necessary for ordinary plant growth and development. BRs share similar chemical structures with animal steroidal hormones, but show a distinctive signal perception mechanism. The importance of BRs is illustrated by the typical phenotypes of mutants with lesions in key biosynthetic or signalling proteins. These mutants show severe dwarfism, curled and round leaves, considerably delayed senescence, reduced male fertility, altered light‐regulated developmental programs, changed responses to abiotic and biotic stresses and modified gene expression profiles. Extensive studies in the last four decades have resulted in a comprehensive picture of BRs, from their nearly completed biosynthesis and physiological functions to their mechanisms of action.
Key Concepts
Brassinosteroids (BRs) are essential plant hormones regulating various developmental processes.
BRs show structures similar to animal steroidal hormones.
Brassinolide is the final product of the BR biosynthetic pathway and the most active BR.
BRs are perceived by transmembrane receptor complexes including the receptor BRI1 and co‐receptor BAK1.
BRs cannot be transported in a long distant manner.
BES1 and BZR1 are the critical downstream transcription factors regulating the expression of thousands of BR response genes.