Regulation of Nitrate Reductase in Barley

通过对大麦硝酸还原酶缺失突变体的筛选和鉴定，证明大麦具有两种硝酸还原酶同工酶，一种是NADH专一性的，另一种是NAD(P)H双特异性的。关于NAD(P)H硝酸还原酶在大麦或其他谷类物种中的重要性或调控，人们知之甚少。这项研究将1)开发专门定量NADH和NAD(P)H硝酸还原酶蛋白质和mRNAs的技术，以及2)利用新开发的定量技术来确定硝酸盐、光和还原氮对硝酸还原酶蛋白质和mRNA的影响。硝酸还原酶mRNAs将用每种硝酸还原酶的cDNA克隆作为特异性探针进行检测。许多高等植物，特别是谷类植物，从土壤中以硝酸盐的形式获得氮素。硝酸还原酶是一种受高度调控的酶，通常被认为是植物硝酸盐同化过程中的关键限制步骤。这项研究将确定调控大麦中特定硝酸还原酶的翻译和转录机制。通过深入了解调节硝酸盐还原的遗传和生化过程，这项研究将有助于提高作物的氮素利用效率。

Through selection and characterization of nitrate reductase deficient mutants it has been demonstrated that barley has two nitrate reductase isozymes, one NADH specific and the other NAD(P)H bispecific. Little is known about the importance or regulation of NAD(P)H nitrate reductases in barley or other cereal species. This research will 1) develop techniques for specifically quantifying NADH and NAD(P)H nitrate reductase proteins and mRNAs, and 2) determine the effects of nitrate, light and reduced nitrogen on nitrate reductase proteins and mRNA using newly developed quantification techniques. Nitrate reductase mRNAs will be determined by using cDNA clones of each nitrate reductase as specific probes. Monoclonal and/or monospecific polyclonal antisera will be used to quantify nitrate reductase proteins.%%% Many higher plants, especially cereals, obtain nitrogen from the soil as nitrate. Nitrate reductase, a highly regulated enzyme, is often considered to be a key limiting step in the nitrate assimilation process in plants. This research will identify translational and transcriptional mechanisms which regulate specific nitrate reductase in barley. By developing a thorough understanding of the genetic and biochemical processes regulating nitrate reduction this research will contribute to improved nitrogen use efficiency in crop plants.***//