Arabidopsis gls mutants and distinct Fd-GOGAT genes:: Implications for photorespiration and primary nitrogen assimilation
Arabidopsis gls mutants and distinct Fd-GOGAT genes:: Implications for photorespiration and primary nitrogen assimilation
复制标题
DOI：
10.1105/tpc.10.5.741
复制
发表时间：
1998-05-01
期刊：
影响因子：
11.6
通讯作者：
Coruzzi, GM
中科院分区：
文献类型：
--
作者：
Coschigano, KT;Melo-Oliveira, R;Coruzzi, GM
铁氧还蛋白依赖性谷氨酸合成酶（M-GOGAT）在拟南芥的光呼吸中起着重要作用，这已经被Fd-GOGAT酶活性（gls）缺陷突变体的特征所确定。尽管遗传证据表明单个Fd-GOGAT位点和基因，但我们发现拟南芥含有两个Fd-GOGAT表达基因（GLU1和GLU2）。gls1位点和GLU基因的物理和遗传定位表明，GLU1与gls1位点相连，而GLU2与另一条染色体相连。GLU1和GLU2表达模式的差异解释了为什么Fd-GOGAT两个基因中只有一个基因突变会导致gls1突变体出现光呼吸表型。GLU1 mRNA在叶片中表达量最高，且受光照和蔗糖的特异性诱导。相比之下，glu2mrna在叶片中的表达水平较低，并优先在根中积累。虽然这些结果表明GLU1在光呼吸中起主要作用，但蔗糖诱导叶片中GLU1 mRNA也表明在初级氮同化中起作用。在抑制光呼吸的条件下，gls突变体的叶绿素水平明显低于野生型，这一发现支持了这一可能性。突变体分析和基因调控研究表明，GLU1基因在光呼吸中起主要作用，也在叶片的初级氮同化中起作用，而GLU2基因可能在根系的初级氮同化中起主要作用。
Ferredoxin-dependent glutamate synthase (M-GOGAT) plays a major role in photorespiration in Arabidopsis, as has been determined by the characterization of mutants deficient in Fd-GOGAT enzyme activity (gls), Despite genetic evidence for a single Fd-GOGAT locus and gene, we discovered that Arabidopsis contains two expressed genes for Fd-GOGAT (GLU1 and GLU2). Physical and genetic mapping of the gls1 locus and GLU genes indicates that GLU1 is linked to the gls1 locus, whereas GLU2 maps to a different chromosome. Contrasting patterns of GLU1 and GLU2 expression explain why a mutation in only one of the two genes for Fd-GOGAT leads to a photorespiratory phenotype in the gls1 mutants. GLU1 mRNA was expressed at the highest levels in leaves, and its mRNA levels were specifically induced by light or sucrose. In contrast, GLU2 mRNA was expressed at lower constitutive levels in leaves and preferentially accumulated in roots. Although these results suggest a major role for GLU1 in photorespiration, the sucrose induction of GLU1 mRNA in leaves also suggests a role in primary nitrogen assimilation. This possibility is supported by the finding that chlorophyll levels of a gls mutant are significantly lower than those of the wild type when grown under conditions that suppress photorespiration, Both the mutant analysis and gene regulation studies suggest that GLU1 plays a major role in photorespiration and also plays a role in primary nitrogen assimilation in leaves, whereas the GLU2 gene may play a major role in primary nitrogen assimilation in roots.