Biochemical and genetic analysis of brassinosteroid metabolism and function in Arabidopsis

Recent analysis of several constitutive photomorphogenic Arabidopsis mutants, defective in brassinosteroid biosynthesis or signaling, provided unequivocal evidence for the essential phytohormone function of brassinosteroids. From earlier studies a wealth of information is available regarding the occurrence of these steroids and their potential interaction with regulatory mechanisms controlled by other plant hormones. In addition, the major pathways of brassinosteroid biosynthesis and metabolism have been clarified in the past couple of years and significant efforts have been made to characterize structure-function relationships. This knowledge is now being confronted with data emerging from genetic and molecular analysis of the gene mutations and functions affecting brassinosteroid synthesis and signaling. Future progress in this field is expected to give insight into the evolution of steroid hormone regulation in eukaryotes, as well as the mechanisms by which brassinosteroids control basic functions, such as cell elongation, morphogenesis and stress responses.