Use of nitrate and ammonium at elevated CO2 in Arabidopsis

植物生长发育需要土壤中以硝酸盐和铵形式存在的氮素。硝酸盐是生长在温带土壤中的植物可利用的主要氮素形式，但最近环境条件的变化选择性地抑制了植物将硝酸盐转化为地上部分的蛋白质的能力。植物可能通过促进根中硝酸盐和铵的蛋白质合成来补偿这种抑制。目前，不仅关于植物对各种氮源的依赖程度的信息很少，而且关于植物在哪里合成蛋白质的信息也很少。研究人员将进行测量，以评估不同基因型的模式植物拟南芥的地上部和根部蛋白质的合成。基因组分析将确定与这些过程相关的基因。这些信息将为植物如何适应不断变化的环境条件提供新的见解。这项研究将考察(A)硝酸盐和铵同化为蛋白质之间的平衡，(B)地上部和根硝酸盐同化之间的平衡，以及(C)在96个或更多的拟南芥天然材料中这些平衡的遗传调节。对二氧化碳、氧气和水通量的测量将提供对新梢中硝酸盐和铵同化之间平衡的实时、非破坏性估计。木质部汁液组成将反映地上部和根部硝酸盐同化的平衡。地上部总氮、游离硝酸盐和生长的变化将表明在过去50年和预计在未来50年发生的各种环境条件下，氮源和硝酸盐同化地点对植物生产力的相对重要性。岭回归全基因组关联(GWA)作图和共表达网络分析将确定与这些性状相关的候选基因。候选基因的验证将包括评估在硝酸盐和铵营养下的单基因T-DNA敲除系，以及RNA-Seq分析，以确定哪些基因在T-DNA敲除中表现出变化的表达。这项研究对于理解过去的变化和预测未来植物性能的变化至关重要。

Plants require nitrogen, in the form of nitrate and ammonium in the soil, for their growth and development. Nitrate is the major form of nitrogen that is available to plants growing in temperate soils, but recent changes in environmental conditions selectively inhibit plants' ability to convert nitrate into protein in above-ground shoots. Plants may compensate for this inhibition through enhanced synthesis of proteins from nitrate and ammonium in the roots. Currently, information is sparse not only about the degree to which plants rely on various nitrogen sources, but also about where plants synthesize protein. The researchers will make measurements to assess shoot versus root synthesis of protein in diverse genotypes of the model plant species Arabidopsis. Genomic analyses will identify the genes that are associated with these processes. This information will provide new insights about how plants can adapt to changing environmental conditions. Ultimately this information may be used to breed crop plants better adapted to particular environments.This research will examine (a) the balance between nitrate and ammonium assimilation into protein, (b) the balance between shoot and root nitrate assimilation, and (c) the genetic regulation of these balances in a population of 96 or more Arabidopsis natural accessions that vary in growth under nitrate and ammonium nutrition. Measurements of carbon dioxide, oxygen, and water fluxes will provide real-time, non-destructive estimates of the balance between nitrate and ammonium assimilation in the shoots. Xylem sap composition will indicate the balance between shoot and root nitrate assimilation. Changes in shoot total nitrogen, free nitrate, and growth will suggest the relative importance of nitrogen source and site of nitrate assimilation on plant productivity under the range of environmental conditions that have occurred over the past fifty years and are anticipated during the next fifty. Ridge-regression genome wide association (GWA) mapping followed by co-expression network analysis will identify candidate genes associated with these traits. Validation of candidate genes will include assessment of single gene T-DNA knockout lines under nitrate and ammonium nutrition and RNA-Seq analysis to determine which genes show altered expression in the T-DNA knockouts. This research is critical to the understanding of past changes and to predicting future changes in plant performance.