Poster: Hormones

Abs # 573: Gibberellin signal transduction in Arabidopsis mediated by the F-box protein SLEEPY1 (SLY1)

Presenter:	Ritchie, Sian , sianrit@yahoo.com
Authors	Ritchie, Sian  (A)   Strader, Lucia C (A)   Soule, Jonathan D (A)   McGinnis, Karen M (B)   Steber, Camille M (A)
Affiliations:	(A): Washington State University (B): University of Arizona

sleepy1 is an Arabidopsis thaliana mutant with a Gibberellin (GA)-insensitive phenotype. These dwarf plants exhibit poor germination and fertility, and neither of these characterstics can be rescued by adding GA. Both the sly1 alelles we have are recessive, and hence the sleepy protein is a positive element in the GA response pathway of Arabidopsis. Cloning of SLEEPY1 revealed that it encodes an F-box protein that is presumably part of an SCF (SKP1, Cullin, F-box) complex (McGinnis et al., Plant Cell, in Press). This complex targets proteins for ubiquitination and degradation by the 26S proteasome. The F-box subunit determines target specificity. Arabidopsis has a large number of F-box genes, but only one other is similar to SLY1. Hence we have named it SLY2. We are investigating if this is also involved in the GA response pathway. Using a combination of Yeast 2-hybrid and co-immunoprecipitation, our goal is to identify the other proteins in the SCF-SLY1 complex. At the same time we are using these techniques to look for other proteins that interact with SLY1 both up and downstream in the GA signaling pathway. In addition, we have initiated a series of new mutant screens- 1.) to identify new SLY1 alleles, enabling us to carry out structure-function analysis of the SLY1 protein, and 2.) to look for suppressors of the sly1 mutant phenotype in an effort to identify other components in the GA signaling pathway.