Recent Advances in Molecular Genetic Studies of the Functions of Brassinolide, A Steroid Hormone in Plants

This chapter reviews the current understanding of the functions of the genes involved in brassinosteroid (BR) metabolism and response and discusses new efforts toward the genetic identification of additional components involved in BR action. Recent molecular genetic studies have demonstrated the biological role of BRs in plant development and have led to the identification of genes encoding BR biosynthetic and metabolic enzymes, a putative BR receptor, and a cellular target of BR signaling. Some of these genes have revealed evolutionary conservation in the biosynthesis, metabolism, and signal transduction mechanisms of steroid hormones between plants and animals. Molecular studies of the regulation and function of these genes in Arabidopsis have started to unravel the underlying mechanism of BR homeostasis and signal transduction. Novel genetic screens are yielding additional mutant effects in BR responses and will lead to the identification of new components involved in BR action.