玉米氨基酸代谢途径关键基因及其调控对氮肥利用率的影响

Grain yields of maize are highly responsive to supplemental nitrogen, with significant amounts of nitrogen fertilizer required annually to maintain high yields. High usage of fertilizer not only increases crop input costs, but also negatively impacts the environment by altering water quality. The development of maize cultivar with high nitrogen use efficiency is the best means to reduce the amount of supplemental nitrogen fertilizer and achieve maximal yields. The previous study has revealed that the expression abundance of around 150 genes involved in amino acid metabolism pathway are responsible for nitrogen status in maize plant, however, the roles of these gene in NUE have not been determined yet. The proposal is aiming at identifying and characterizing the genes responsible for nitrogen use efficiency (NUE) in amino acid metabolism pathway using a recombinant inbred lines (RIL) population in maize. We will apply dynamic molecular techniques to construct the saturated genetic linkages and identify gene structures, mRNA expression, amino acid abundance and grain carbon/nitrogen components that associate with nitrogen use efficiency in maize under different nitrogen conditions, and using many different types of experimental or predicted data and a set of RIL. The technologies and results will show much promise as a means to analyze and better understand the interactions within NUE. The greatest contribution of bioinformatic analysis including various QTL mapping outcomes will be benefitial for better understanding of the genetic architecture of quantitative traits to improve NUE for Chinese crop cultivars.

氮肥的大量施用，在提高玉米产量的同时，也导致生产成本增加和环境污染加剧。遗传研究玉米氮素利用的分子调控机制将为培育氮高效品种提供重要理论依据。对玉米不同发育时期及其器官表达谱研究发现，多个氨基酸代谢途径基因mRNA的表达丰度与氮肥施用量有关，但这些基因对植物氮肥利用率（NUE) 是否存在贡献及贡献大小尚未明确。本项目将利用玉米IBM重组自交系群体，遗传分析其氨基酸代谢途径关键基因DNA结构，确定高氮和低氮肥条件下氨基酸代谢途径关键基因表达eQTL和游离氨基酸含量QTL，并对eQTL和游离氨基酸含量QTL与籽粒碳氮组成成分、产量形成和NUE的关联性进行分析，同时利用农杆菌转基因法对决定NUE关键基因进行功能验证，以期从多个层面解析影响玉米NUE的氨基酸代谢途径及关键基因，为玉米氮高效利用的分子设计育种提供理论依据。

玉米在生长季中需要吸收大量的氮肥，提高氮肥的利用率不但可以减少生产投入，还能降低氮肥流失对环境产生的负面影响。本研究利用玉米IBM重组自交系群体，结合二代测序和分子标记技术，获得了高密度的遗传图谱，结合测量籽粒发育的氨基酸含量、蛋白含量和产量数据，发现了控制籽粒蛋白的QTL位点，该位点位于第一条染色体上，含有一个编码天冬酰胺合成酶的基因，过量表达该基因可以提高籽粒发育时期天冬酰胺的含量，可促进玉米醇溶蛋白的合成，同时抑制淀粉的积累，相应降低籽粒的重量。同时我们也发现一个在玉米中可以响应外界氮浓度改变的转录因子nlp5,一系列的遗传分析发现该基因可以对部分氮代谢途径关键基因的表达起调控作用。这些关键基因都通过连续回交和分子标记选择导入到郑58和昌7-2的自交系中以评价其在育种中的潜在作用。通过本项目的实施，我们在吸收（根）和利用（籽粒）两个关键组织解析玉米氮肥利用率（NUE)的构成，为玉米氮高效利用的分子设计育种提供理论依据。

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