USE OF ARABIDOPSIS MUTANTS AND GENES TO STUDY AMIDE AMINO-ACID BIOSYNTHESIS
USE OF ARABIDOPSIS MUTANTS AND GENES TO STUDY AMIDE AMINO-ACID BIOSYNTHESIS
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DOI：
10.1105/tpc.7.7.887
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发表时间：
1995-07-01
期刊：
影响因子：
11.6
通讯作者：
CORUZZI, G
中科院分区：
文献类型：
--
作者：
LAM, HM;COSCHIGANO, K;CORUZZI, G
高等植物氮同化酶的研究对基础和应用植物研究都有影响。首先，这一领域的基础研究应该揭示植物调节参与代谢途径的基因的机制。第二，因为氮是植物生长的限速元素（Hageman和Lambert，1988年），通过对与氮同化有关的基因进行分子或遗传操作，有可能提高作物的产量或改善作物的品质。氮同化为氨基酸的研究由于以下事实而变得复杂，即这些反应中的一些是由位于不同亚细胞中的多种同工酶催化的。隔间用传统的生物化学方法，很难弄清植物氮代谢中各同工酶的功能。谷氨酰胺合成酶（GS）的叶绿体和胞质同工酶的基因在不同的细胞类型中表达的发现（Edwards等人，1990; Carvalhoet等人，1992; Kamachi等人，1992）指出，传统的生物化学研究开始于组织破坏，人为地混合了在体内同一细胞类型中可能不共存的同工酶。因此，在体外生物化学方法通常用于定义限速酶在单细胞微生物的途径可能会导致错误的解释时，用于研究植物代谢途径。定义特定同工酶的体内功能或定义途径中的限速酶的另一种方法是通过突变体分析，如大肠杆菌和酵母的研究所示。在拟南芥和大麦中筛选光呼吸突变体时，已经鉴定出GS或铁氧还蛋白依赖性谷氨酸合酶（Fd-GOGAT）的特定同工酶缺陷的植物突变体（萨默维尔和Ogren，1980，1982; Wallsgrove等，1987年）。最近，已经使用不依赖于生长表型的筛选方法鉴定了具有氮同化的另外的酶的活性改变的拟南芥突变体（Schultz和Coruzzi，1995）。突变同工酶的体内作用
Studies of enzymes involved in nitrogen assimilation in higher plants have an impact on both basic and applied plant research. First, basic research in this area should uncover the mechanisms by which plants regulate genes involved in a metabolic pathway. Second, because nitrogen is a rate-limiting element in plant growth (Hageman and Lambert, 1988), it may be possible to increase the yield or improve the quality of crop plants by the molecular or genetic manipulation of genes involved in nitrogen assimilation.Research on nitrogen assimilation into amino acids has been complicated by the fact that some of these reactions are catalyzed by multiple isoenzymes located in distinct subcellular compartments. With traditional biochemical approaches, it has been impossible to sort out the function of each isoenzyme in plant nitrogen metabolism. The discovery that genes for chloroplastic and cytosolic isoenzymes of glutamine synthetase (GS) are expressed in distinct cell types (Edwards et al., 1990; Carvalhoet al., 1992; Kamachi et al., 1992) suggeststhat traditional biochemical studies, which begin with tissue disruption, artificially mix isoenzymes that may not coexist in the same cell type in vivo. Thus, in vitro biochemical methods commonly used to define the rate-limiting enzyme in a pathway in unicellular microorganisms may lead to erroneous interpretations when employed to study plant metabolic pathways. An alternative way to define the in vivo function of a particular isoenzyme or to define a rate-limiting enzyme in a pathway is by mutant analysis, as shown by studies of Escherichia coli and yeast. Plant mutants defective in particular isoenzymes of GS or ferredoxin-dependent glutamate synthase (Fd-GOGAT) have been identified in screens for photorespiratory mutants in Arabidopsis and barley (Somerville and Ogren, 1980, 1982; Wallsgrove et al., 1987). More recently, Arabidopsis mutants with alterations in the activity of additional enzymes of nitrogen assimilation have been identified using a screening method that does not depend on a growth phenotype (Schultz and Coruzzi, 1995). The in vivo role of the mutated isoenzyme