Protein phosphorylation is a major mode of regulation of metabolism, gene expression, and cellular architecture in eukaryotic cells, and defining phosphorylation-based regulatory networks is essential for understanding the function of the Arabidopsis genome. The goal of this project is to define phosphorylation networks that are related to the function of calcium-dependent protein kinases (CDPKs) and four closely related families; CDPK-related kinases (CRKs), phosphoenolpyruvate carboxylase kinases (PPCKs), PPCK-related kinases (PEPRKs), and SNF-1 related kinases (SnRKs). These 88 kinases, which represent about 9% of all the protein kinases in the Arabidopsis genome, are involved in all aspects of plant development and physiology and participate in the coupling of cellular responses to environmental and developmental signals. A list of these protein kinases including gene identification numbers is available at www.arabidopsis.org, and further information including links to database records is available at http://plantsp.sdsc.edu. This research will investigate the function of 64 members of these families through determination of the subcellular location of each kinase and identification of downstream targets and other proteins with which the kinases associate. This information will give insight into the physiological roles of each kinase by identifying signaling networks in which each participates. This research will also determine the target sequences in substrate proteins that are phosphorylated by each kinase, and these results will contribute to understanding the overlap in kinase function and cross-talk between signaling pathways. The results of this work will be made available on a yearly basis at the two URLs given above.
