Department of Biological Sciences, University of Warwick, CV4 7AL, Coventry, UK.
Planta. 1991 Dec;183(1):51-6. doi: 10.1007/BF00197566.
In the legume Phaseolus vulgaris L., glutamine synthetase (GS; EC.6.3.1.2.) is encoded by four actively transcribed genes, gln-α, gln-β, gln-γ and gln-δ. We have studied the expression of these genes in cotyledons during seed germination and have studied the effect of light and nitrate on this process. An RNase-protection method, used to detect the abundances of GS mRNAs, revealed that the four GS genes are differentially expressed in the germinating cotyledons. The gln-α. mRNA was present in dry seeds and was the most abundant GS mRNA during early stages of germination. The gln-β and gln-γ mRNAs were first detectable 2 d after sowing and their abundances differed in light- and dark-grown cotyledons at later stages of germination. The gln-δ mRNA (which encodes the plastid-located GS) was detectable only in light-grown cotyledons, at a low abundance. A nitrate supply of 2 mM had only a minor effect on the expression of the GS genes. Western immunodetection and ion-exchange high-performance liquid chromatography demonstrated that the α polypeptide and isoenzyme were present in extracts of dry seeds and represented the major GS products at 2 d and 4 d. Both the β and γ polypeptides appeared at the 2-d stage. The role of differential GS gene expression in controlling cotyledonary GS activity is discussed.
在豆科植物菜豆（Phaseolus vulgaris L.）中，谷氨酰胺合成酶（GS；EC.6.3.1.2.）由四个活跃转录的基因编码，分别是 gln-α、gln-β、gln-γ 和 gln-δ。我们研究了这些基因在种子萌发过程中子叶中的表达情况，并研究了光和硝酸盐对这一过程的影响。一种用于检测 GS mRNA 丰度的 RNase 保护法表明，在萌发的子叶中，这四个 GS 基因的表达存在差异。gln-α mRNA 存在于干种子中，并且在萌发的早期阶段是最丰富的 GS mRNA。gln-β 和 gln-γ mRNA 在播种后 2 天首次可检测到，并且在萌发后期的光和暗培养子叶中它们的丰度不同。gln-δ mRNA（编码质体定位的 GS）仅在光培养的子叶中可检测到，丰度较低。2 mM 的硝酸盐供应对 GS 基因的表达只有很小的影响。Western 免疫检测和离子交换高效液相色谱法表明，α 多肽和同工酶存在于干种子提取物中，在 2 天和 4 天代表主要的 GS 产物。β 和 γ 多肽均在 2 天阶段出现。讨论了差异 GS 基因表达在控制子叶 GS 活性中的作用。
