Project Number: 5348-21000-019-01
Project Type: Trust

Start Date: Sep 01, 2002
End Date: Aug 31, 2005

Objective:
1. Determine if Sly1 is a component of an SCF E3 ubiquitin ligase complex that transmits the GA signal. 2. Determine if Rga and Gai are SCF-Sly1 substrates.

Approach:
This proposal investigates the role of the gene SLEEPY1 (SLY1) in the signaling pathway of the plant hormone gibberellin (GA) in Arabidopsis thaliana. Loss of SLY1 function results in the full range of phenotypes expected in a GA-insensitive mutant including dwarfism, reduced fertility and increased seed dormancy. SLY1 is one of the few positive regulators of GA response identified to date. We recently cloned the SLY1 gene and found that it encodes a 151 amino acid protein that resembles the F-box subunit of the SCF E3 ubiquitin ligase. This result is evidence that the GA signaling, like auxin, may be regulated by the ubiquitin-targeted protein breakdown. This hypothesis will be tested by determining whether the Sly1 protein binds to other SCF proteins. We will accomplish this by determining if SCF complex proteins co-purify with Sly1 using yeast 2-hybrid and co-immunoprecipitation. GA signaling is negatively regulated by the transcription factors Rga and Gai. Rga and Gai proteins are 82% identical to one another, and are both needed to repress stem elongation. Several lines of evidence indicate that Rga is a likely substrate for GA-regulated protein break down. This project will use two approaches to determine if Rga and Gai are SCF-Sly1 substrates. First it will test if SLY1 expression levels correlate with Rga and Gai protein levels. Second, it will determine if the rga-24 gai-t6 double mutant can suppress the sly1 mutant phenotype. Documents Trust with NRI-CGP. Log 21293.Formerly 5348-21000-016-06T (9/03).

Project Team

Steber, Camille

Project Annual Reports

FY 2003