Symposium III: Hormone Crosstalk

Abs # 30002: Light, brassinosteroids, and Arabidopsis development

Presenter:	Chory, Joanne , chory@salk.edu
Authors	Chory, Joanne  (A)   Cano-Delgado, Ana  (A)   Mora-Garcia, Santago  (A)   Nemhauser, Jennifer  (A)   Vert, Gregory  (A)   Wang, Xuelu  (A)   Wu, Guang  (A)   Yin, Yanhai  (A)
Affiliations:	(A): Plant Biology Laboratory, The Salk Institute and Howard Hughes Medical Institute, La Jolla, CA 92037

Brassinosteroids are a class of plant hormones that induce a broad spectrum of developmental responses, such as stem elongation, pollen tube growth, leaf bending and epinasty, root growth inhibition, and xylem differentiation. We are taking a combined genetic, biochemical, and molecular approach in Arabidopsis to identify components of the brassinosteroid signal transduction pathways. A class of mutants that we study show many characteristics of light-grown plants even when grown in complete darkness. We have recently shown that these mutations define genes involved in brassinosteroid biosynthesis, metabolism, or signaling. A transmembrane receptor serine/threonine kinase, BRI1, functions as the receptor for brassinosteroids. Binding of the steroid requires the extracellular domain of BRI1 and induces its autophosphorylation. The signal transduction pathway from BRI1 involves both novel and known proteins and is branched. One branch controls rapid changes in the rate of cell elongation through regulated assembly of the V-ATPase, while the second branch involves changes in gene expression which control cell expansion and other processes. The complex interactions between light, auxin, and steroid signaling in regulating Arabidopsis development will be discussed.