Asparagine metabolism and function in nitrogen signalling

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Seed protein accumulation is dependent on the supply of nitrogen to the developing embryo, which influences the partitioning of carbon into the different storage products. Asparagine is a major form of nitrogen commonly transported to sink tissue. In leaf, asparagine is also transiently accumulated at night when, in the absence of photosynthesis, levels of organic acids are insufficient for nitrogen assimilation. The objectives of this proposal are to achieve a detailed understanding of asparagine metabolism and of the function and perception of asparagine as a metabolite signal in plants. The proposed project will seek to understand the physiological and metabolic basis underlying the inhibition of root elongation by asparagine, and to characterize the signalling network determining changes in gene expression elicited by asparagine. Control of asparagine biosynthesis during the day and night cycle by phosphorylation of the asparagine biosynthetic enzyme asparagine synthetase will also be investigated. An integrated approach including cellular biology, molecular genetics, metabolite profiling, enzymology and characterization of post-translational modifications will be used to address these goals. The proposed research should improve our understanding of plant nitrogen metabolism and may lead to biotechnological strategies to manipulate the levels of storage products in grain or to enhance nitrogen use efficiency in crops.