Poster: Hormones

Abs # 641: Functional Analysis of Cotton Genes Involved in the Brassinosteroid Signal Transduction Pathway

Presenter:	Yan, Sun , ysun@ttu.edu
Authors	Yan, Sun  (A)   Fokar, Mohamed  (A)   Allen, Randy  (A)
Affiliations:	(A): Texas Tech University

Brassinosteroids (BR) are polyhydroxylated sterol derivatives of plant origin that are required for normal plant development. Our preliminary work with the BR biosynthesis inhibitor BRZ2001 has shown that BR signaling is necessary for cotton fiber initiation and elongation. Several Arabidopsis genes that encode critical components of this pathway have been identified through genetic screening. BRI1 encodes a membrane-bound leucine-rich receptor-like protein kinase that apparently acts as the BR receptor. BIN2, a second gene in this pathyway, encodes a shaggy-like protein kinase that down-regulates BR signaling. We identified cotton ESTs similar to the Arabidopsis BRI1 and BIN2 genes, and these ESTs were used to clone the corresponding full length cotton cDNAs. Analysis of the expression patterns of these genes using quantitative real-time PCR showed that they are expressed throughout cotton plants, including leaves, buds, stems, roots, sepals, ovules, bolls, and fibers. To identify the functions of these genes, we developed gene constructs that express cotton BRI1 and BIN2 under control of a CaMV 35S promoter. Expression of the cotton BRI1 transgene in the dwarf bri1-5 mutant Arabidopsis plants restored them to normal height. Conversely, expression of the cotton BIN2 transgene in wildtype Arabidopsis plants resulted in severe stunting similar to strong BR deficient or insensitive mutants. These results confirm that the cotton BRI1 and BIN2 cDNAs encode proteins that are capable of functioning in the BR signaling pathway.