Signaling by Ethylene Receptors of Arabidopsis

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The gas ethylene functions as an endogenous growth regulator in plants, affecting seed germination, seedling growth, abscission, senescence and fruit ripening. The initial steps by which plants perceive and transduce the ethylene signal have begun to be elucidated by studies in Arabidopsis thaliana. It has been found that plants contain a family of ethylene receptors that are related to bacterial histidine kinases. Downstream of the receptor is a MAP kinase pathway. The research in this project is studying how the ethylene signal is transduced through the receptor and passed on to other elements in the signaling pathway. The membrane localization of ethylene receptors in plants will be determined by expression of fusions with green fluorescent protein (GFP) in Arabidopsis.Dynamics of receptor expression and localization will be examined by use of biochemical methods in concert with visualization of GFP fusions. Phosphorylation activity of the receptors will be examined after transgenic expression and purification from yeast. The mechanisms of action of the ethylene receptors will be examined by transforming mutant versions back into Arabidopsis and determining how ethylene signal transduction is affected. This work will clarify early steps in ethylene signal transduction and provide a framework for engineering modifications into these steps. Modifications of ethylene sensitivity will enhance our ability to regulate such processes as abscission and fruit-ripening of crops. These studies will also help to understand how bacterial histidine kinases have been adapted to function in a eukaryotic system.