G protein signaling in the plant response to environmental stress

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This research proposal is directed toward understanding of stress tolerance in plants through the characterization of specific protein-protein interactions in the regulation heterotrimeric G protein signaling and the regulation of the nuclear RAN-GTPase. The characterization of these regulatory proteins will be an important step forward in understanding the molecular basis of stress tolerance and improving the tolerance of plants. Unpredictable changes in climatic conditions, including drought and extreme temperatures pose challenging and costly risks to agriculture. Plants have a wide genetic variation for stress tolerance and throughout the history of agriculture there as been genetic selection for improved yield under stress conditions. The need to improve tolerance in plants augmented by changing climatic conditions and the success in achieving improvements will be dependent on understanding the biological mechanisms underpinning this tolerance. My laboratory has identified a large number of regulatory genes in bread wheat (Triticum aestivum) that are more strongly induced by stress conditions in tolerant genotypes than in sensitive genotypes. We have identified calcium binding proteins Clo3 and Clo7, a salt, drought and ABA induced gene Esi2, and a phospholipase C proteins that interact with two classes G proteins, the alpha subunit of the heterotrimeric protein complex and the RAN GTPase. Because these classes of G proteins play central roles in signaling, nuclear import and export and in cell division we have focused our work on these proteins. We hypothesize that these protein-protein interactions contribute to the cell's adaptation to stress by down-regulating the activity of these two classes of G proteins. We have shown that the homologs of these proteins in Arabidopsis interact in the same manner as the wheat proteins. We propose to use the powerful genetic tools available in Arabidopsis to advance our understanding of the basic genetic and molecular mechanisms that control G proteins signaling and to investigate the role of these protein-protein interactions in improving environmental stress tolerance in plants.