Networks of Heterotrimeric G alpha Subunit Signaling to K+ Channels in Arabidopsis Guard Cells

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G proteins, which are composed of three smaller proteins named Galpha, Gbeta, and Ggamma, are important and ubiquitous cellular proteins in animals, fungi, and plants. Signaling pathways that are coupled to G proteins allow these organisms to sense and respond appropriately to their environments. In plants, G proteins help plant cells to sense both pathogenic bacteria and water stress. One of the best understood cellular systems of G protein regulation in plants is the stomatal guard cell. Guard cells are highly specialized cells found in the outermost tissue layer (the epidermis) of the leaf. Pairs of guard cells regulate the opening and closing of microscopic pores called stomata, through which plants take up carbon dioxide from the air for photosynthesis but through which they also lose water vapor to the atmosphere, leading potentially to dehydration stress. The guard cells control the aperture of the stomata by changing their shape and volume, processes that are in turn controlled by the uptake of potassium and other solutes. Proteins (KAT1) in the guard cell membrane mediate the uptake of potassium which drives this stomatal opening. KAT1 protein activity is inhibited by the plant hormone abscisic acid (ABA) and by molecules produced by bacteria that cause plant disease. G proteins serve as "middle-men" that relay the signals from ABA and bacteria to the KAT1 proteins, but G proteins are only one component of the complex intracellular signaling networks underlying these responses. This project will elucidate in detail the networks of intracellular signaling proteins that relay signals (for example from ABA) to G proteins and on to KAT1. An integral component of this research is the development of new and broadly applicable computational tools for understanding and predicting cellular signaling networks. BROADER IMPACTS: This research has significance for plant biology (and more broadly for society) because it will help develop crops with improved resistance to infection and to environmental stress. The computational approaches developed by this research will be broadly applicable to any cellular signaling network, regardless of organism. This project will provide interdisciplinary training to undergraduate and graduate students and post-doctoral fellows at the interface of cell and computational biology. Project personnel will work towards improving the representation of minorities in science by participating in outreach and mentoring activities at the annual SACNAS (Society for the Advancement of Chicano/a and Native American Scientists) conference.This project is supported jointly by the Networks and Regulation and Mathematical Biology Programs.