Asparagine metabolism and function in nitrogen signaling

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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 key transport form of nitrogen in higher plants. The enzyme asparaginase is hypothesized to play a critical role in the supply of nitrogen to sink tissues including developing seeds. This enzyme breaks down asparagine into aspartate and ammonia, which is re-assimilated and used in the synthesis of other amino acids. A correlation between free asparagine levels in developing seeds and protein content at maturity has been observed in soybean and cereals, suggesting a possible role of asparagine as a metabolite signal regulating protein accumulation. The objectives of this proposal are to achieve a detailed understanding of asparagine catabolism in higher plants, and of asparagine function and perception as a nitrogen metabolite signal. Approaches including the study of enzyme structure and function, molecular genetics, transcript and metabolite profiling, and metabolic biochemistry will be used to address this goal. The proposed research should improve our understanding of the process of seed nitrogen supply, and may lead to biotechnological strategies to manipulate the levels of storage products, either to enhance nutritional value or for bio-industrial applications.