Poster: Integrative plant physiology

Abs # 35: Unique AAA ATPases that control plant responses to stress

Presenter:	Ramadevi, Saddikuti , ramadevi@iastate.edu
Authors	Ramadevi, Saddikuti  (A)   Xiang, Chengbin  (A)   Oliver, David J (A)
Affiliations:	(A): Iowa State University

Activation sequence (as-1) elements play a crucial role in the activation of defense genes in response to multiple stress stimuli such as JA, SA, xenobiotics, hydrogen peroxide and heavy metals. How these diverse stress signals converge on a particular cis element remains unclear. In an effort to study the stress signaling pathways that involve as-1 elements and TGA factors, an Arabidopsis reporter line was generated by transforming with pCB105 vector containing uidA reporter gene under the control of four tandem repeats of nos-1 element and the reporter line was mutagenized with T-DNA insertional mutagenesis. We have isolated several up-regulated and down-regulated stress responsive mutants of Arabidopsis. Three independent up-regulated mutant lines have a knock out mutation in one AAA (ATPases Associated with various cellular Activities) ATPase locus. Based on the sequence homology, this tagged gene together with its twenty closely related members in Arabidopsis forms a novel group of AAA ATPase genes unique to plants. Under certain stress conditions, the mutant plants performed better than wild type plants. The expression of stress related genes was also up-regulated in mutant plants in response to stress and this activation appears to be confined to the genes with as-1 elements in their promoter. These results suggest that this protein is involved in regulating the as-1/TGA mediated gene expression. Based on our experiments, we propose a model in which this AAA ATPase switch off the activated transcription of stress related genes by causing the dissociation of the as-1/TGA complex. This study offers an insight into a new mechanism in transcriptional regulation as well as expands our limited knowledge on the functions of AAA ATPases in plants.