Poster: Hormones

Abs # 613: A Genome-Wide Systematic Approach to Dissecting Gibberellin Signaling in Rice & Barley Aleurone Cells

Presenter:	Shen, Jeff , jeffery_shen@ccmail.nevada.edu
Authors	Shen, Jeff  (A)   Zhang, Zhonglin  (A)   Xie, Zhang  (A)   Zou, Xiaolu  (A)   Tchakarski, Polet  (A)   Ruas, Paul  (A)   Shen, Kate  (A)   Wu, Wei  (A)
Affiliations:	(A): University of Nevada

Gibberellins (GA) regulate several aspects of plant development such as germination, plant growth and flowering. We have taken an integrative approach to study GA signal transduction by "data-mining" the rice genome sequences for putative GA signaling/responsive genes and functionally analyzing intron-containing regulatory molecules in barley aleurone cells. This combinatory approach has allowed us to identify 77 OsWRKY genes, with three of them functioning as negative regulators of GA response pathways in aleurone cells. OsWRKY24, OsWRKY71 and OsWRKY72 suppress GA-induced alpha-amylase expression in a dosage-dependent manner. Mutagenesis studies indicate that the suppression activity relies on the C-terminal fragment downstream of the WRKY domain. Consistent with their roles as repressors of GA signaling, the expression of OsWRKY24 and OsWRKY71 is down-regulated by GA and the corresponding proteins are targeted to nuclei of aleurone cells. Double-stranded RNA interference (RNAi) inhibition of the OsWRKY synthesis results in derepression of a-amylase expression even in the absence of GA. Furthermore, OsWRKY24 suppresses the induction of the alpha-amylase gene expression by the GA-inducible transactivator OsGAMyb, indicating this repressor acts at downstream of OsGAMyb. The mechanisms by which these transcription regulators modulate GA response will be addressed.