Poster: Hormones

Abs # 647: ABA regulation of transcription factors interacting with ABA response promoter complexes

Presenter:	Casaretto, Jose A., casarett@biology.wustl.edu
Authors	Casaretto, Jose A. (A)   Ho, Tuan-hua D. (A)
Affiliations:	(A): Washington University

The barley bZIP transcription factor HvABI5 mediates ABA-regulated gene expression in barley aleurone cells. HvABI5 specifically recognizes cis-elements of the abscisic acid (ABA) response promoter complexes present in the promoters of the stress-induced genes HVA1 and HVA22. The transactivation of these promoters is dependent on the presence of the transcriptional activator HvVP1, and cannot be blocked by the negative regulator abi1-1. The expression of HvABI5 appeared to be up-regulated by ABA and can be suppressed by abi1-1. Gain- and loss-of-function studies in barley aleurones show that HvABI5 expression is positively controlled by an autoregulatory loop which involves HvABI5 and HvVP1. However, ABA does not play a role in the nuclear localization of HvABI5. Possible transcriptional regulation and post-translational modification of HvABI5 in response to ABA are discussed.