Arabidopsis mutant analysis and gene regulation define a nonredundant role for glutamate dehydrogenase in nitrogen assimilation
Arabidopsis mutant analysis and gene regulation define a nonredundant role for glutamate dehydrogenase in nitrogen assimilation
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DOI：
10.1073/pnas.93.10.4718
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发表时间：
1996-05-14
影响因子：
11.1
通讯作者：
Coruzzi, GM
中科院分区：
文献类型：
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作者：
MeloOliveira, R;Oliveira, IC;Coruzzi, GM
谷氨酸脱氢酶在所有生物体中普遍存在，但其在高等植物中的作用仍是个谜。为了更好地了解GDH在植物氮代谢中的作用，我们鉴定了一个GDH1基因产物缺失的拟南芥突变体(gdh1-1)，并研究了GDH1基因的表达，GDH1基因在暗适应或蔗糖饥饿的植物中积累到最高水平，光或蔗糖处理都抑制了GDH1基因的积累。这些结果表明，在碳限制条件下，GDH1基因产物以谷氨酸分解代谢的方向发挥作用。外源氨可以诱导轻度生长植物叶片中低水平的GDH1基因的表达。在碳和氨过量的条件下，GDH1可能在谷氨酸的生物合成方向发挥作用。拟南芥GDH1基因缺失突变等位基因gdh1-1与GDH1基因共分离，表现为隐性突变。Gdh1-1突变体表现出一种条件表型，在含有外源无机氮的培养基上，幼苗的生长明显受阻。这些结果表明，在无机氮过量的条件下，GDH1在氨的同化过程中起着非多余的作用。进一步支持这一观点的事实是，GDH1和氯化谷氨酰胺合成酶(GS2)的mRNA水平受光的相互调节。
Glutamate dehydrogenase (GDH) is ubiquitous to all organisms, yet its role in higher plants remains enigmatic. To better understand the role of GDH in plant nitrogen metabolism, we have characterized an Arabidopsis mutant (gdh1-1) defective in one of two GDH gene products and have studied GDH1 gene expression, GDH1 mRNA accumulates to highest levels in dark-adapted or sucrose-starved plants, and light or sucrose treatment each repress GDH1 mRNA accumulation. These results suggest that the GDH1 gene product functions in the direction of glutamate catabolism under carbon-limiting conditions. Low levels of GDH1 mRNA present in leaves of light-grown plants can be induced by exogenously supplied ammonia. Under such conditions of carbon and ammonia excess, GDH1 may function in the direction of glutamate biosynthesis. The Arabidopsis gdh-deficient mutant allele gdh1-1 cosegregates with the GDH1 gene and behaves as a recessive mutation. The gdh1-1 mutant displays a conditional phenotype in that seedling growth is specifically retarded on media containing exogenously supplied inorganic nitrogen. These results suggest that GDH1 plays a nonredundant role in ammonia assimilation under conditions of inorganic nitrogen excess. This notion is further supported by the fact that the levels of mRNA for GDH1 and chloroplastic glutamine synthetase (GS2) are reciprocally regulated by light.