Grant: Discovery Grants Program - Individual

`Metabolism' refers to all enzyme-catalyzed chemical reactions occurring in a cell. Over the past 37 years my NSERC-funded research program has made important contributions to our understanding of the organization and control of plant carbohydrate and phosphorus metabolism, while training a host of HQP for productive academic and non-academic careers. This has been approached by characterizing the molecular, regulatory, and functional properties of key enzymes (protein catalysts) that control: i) carbon partitioning to storage end-products (i.e., oils & proteins) in developing oilseeds, & ii) plant phosphorus acquisition and use. We are particularly interested in identifying and characterizing covalent modifications (i.e. `post-translational modifications' or PTMs) that occur to most enzymes after they have been synthesized by living cells. This is because PTMs such as phosphorylation or ubiquitination can rapidly control an enzyme's activity, subcellular location, interactions with other proteins, &/or degradation in response to various extra- or intracellular signals. There is indisputable evidence for the pivotal importance of reversible protein PTMs as a major mechanism that integrates signaling, development, metabolism, and stress responses in plant cells. This application requests funding to support integrated biochemical and genetic research with the model plant Arabidopsis thaliana arising from our recent discoveries. This includes assessing the adaptive roles that the non-proteogenic amino acid and `stress' metabolite ?-aminobutyrate (GABA), the GABA metabolizing enzymes glutamate decarboxylase and GABA aminotransferase, and the GABA shunt (a metabolic bypass of the tricarboxylic acid cycle) play during nutritional P deprivation. Our discovery and thorough characterization of calcium-dependent protein kinases (CDPKs) involved in the control of castor oilseed photosynthate partitioning led us to consider the involvement the CDPK isozyme CPK4 and one of its apparent targets, the E3 ubiquitin ligase ATL6, during Arabidopsis acclimation to pathogen infection. Our studies have significant applications to problems in Canadian and worldwide agriculture, sustainable food security, and environmental protection. This includes the development of phosphorus-use efficient crops, urgently needed to reduce mankind's rampant but highly inefficient use of non-renewable, unsustainable, and polluting phosphorus fertilizers. Similarly, understanding how plants sense and acclimate to pathogen infection is facilitating biotechnological approaches to enhancing crop resilience to bacterial pathogens. During this granting period my HQP will continue to integrate innovative biochemical, genomic, and cell biology tools into their research. These advances provide quantitative improvements in the types of hypotheses that we can test, and a solid foundation for HQP training and careers in modern plant sciences.