Use of nitrate and ammonium at elevated CO2 in Arabidopsis

点击翻译按钮获取中文摘要

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.