Asparagine metabolism and function in nitrogen signaling

种子蛋白质的积累依赖于发育中的胚的氮供应，这影响了碳在不同贮藏产物中的分配。天冬酰胺是高等植物氮的主要运输形式。据推测，天冬酰胺酶在向下沉组织（包括发育中的种子）提供氮的过程中起着关键作用。这种酶将天冬酰胺分解成天冬氨酸和氨，再被吸收并用于合成其他氨基酸。在大豆和谷物中发现，发育中的种子游离天冬酰胺水平与成熟时蛋白质含量之间存在相关性，这表明天冬酰胺可能是一种调节蛋白质积累的代谢信号。本研究的目的是详细了解高等植物的天冬酰胺分解代谢，以及天冬酰胺作为氮代谢信号的功能和感知。方法包括酶的结构和功能的研究，分子遗传学，转录和代谢物分析，以及代谢生物化学将被用来解决这一目标。本研究将提高我们对种子氮供应过程的理解，并可能导致生物技术策略来控制储存产品的水平，以提高营养价值或生物工业应用。

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.