Poster: Late and Moved Abstracts

Abs # 994: Exploring the ETR1 Receiver Domain

Presenter:	Shockey, Jason A, jshockey@mail.umd.edu
Authors	Shockey, Jason A (A)   Resnick, Josephine S (A)   Chang, Caren  (A)
Affiliations:	(A): University of Maryland, College Park

Recent studies have suggested that the histidine kinase domain of the ETR1 ethylene receptor may not play a major role in ethylene signal transduction. However, it would be surprising if histidine kinase activity, and subsequent phospho-transfer to the aspartate of the ETR1 receiver domain, had no role in the plant due to the remarkable degree of sequence conservation. While a great deal of work has been done with the histidine kinase and ethylene binding domain of ETR1, little work has focused on the receiver domain. In order to better understand the role of this domain, either in ethylene signaling or other possible functions, we utilized protein interaction studies and transgenic plants in the analysis of mutated receiver domains. Mutant receiver domains were engineered to either prevent phosphorylation (D659A) or to mimic phosphorylation (D659E). Interestingly, the phosphorylation mimic D659E, but not the D659A, disrupts the yeast two-hybrid interaction between ETR1 and the downstream MAPKKK CTR1. Despite this loss of interaction in the yeast two-hybrid assay, both the D659A and D659E mutants are able to restore an etr1 ers1 double null mutant plant to wild-type, indicating the receiver mutations have no effect on signaling. Cross-talk with light and osmolarity sensing pathways were also examined and found to be unaffected. In an assay to measure growth rates of dark-grown seedlings, both mutants show a delayed recovery after dosage with ethylene. We are also currently examining the introduction of mutant forms etr1-1 D659E and etr1-1 D659A into plants lacking all ethylene receptors family members that contain receiver domains.