Repercussion of mesophyll-specific overexpression of a soybean cytosolic glutamine synthetase gene in alfalfa (Medicago sativa L.) and tobacco (Nicotiana tabaccum L.).
Repercussion of mesophyll-specific overexpression of a soybean cytosolic glutamine synthetase gene in alfalfa (Medicago sativa L.) and tobacco (Nicotiana tabaccum L.).
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DOI：
10.1016/j.plantsci.2008.10.006
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发表时间：
2009-01
期刊：
影响因子：
5.2
通讯作者：
Gopalan, Champa-Sengupta
中科院分区：
文献类型：
--
作者：
Seger, Mark;Ortega, Jose Luis;Bagga, Suman;Gopalan, Champa-Sengupta
关键词：
谷氨酰胺合成酶（GS）在植物氮代谢中起着核心作用。植物 GS 作为存在于细胞质 (GS1) 或叶绿体/质体 (GS2) 中的许多同工酶而出现。有几份报告表明，由组成型 CaMV35S 启动子驱动的过表达 GS1 转基因的转基因植物的性能得到改善。改进归因于 GS1 转基因产物的功能是增强光呼吸或蛋白质降解释放的 NH4+ 的再同化。在本文中，将表达由光合细胞特异性启动子驱动的大豆基因的苜蓿和烟草转化体与具有由更强的CaMV35S启动子驱动的相同转基因的转化体进行了比较。苜蓿和烟草两类转化体的GS1转录物和GS1蛋白积累水平存在差异，但总GS活性差异较小。转基因表达水平和 GS 活性的差异归因于全蛋白稳定性水平的翻译后调节。两类转化体在可溶性蛋白质以及光合作用和光呼吸速率方面均表现出相似水平的改善。该数据支持这样的假设：叶肉细胞中产生的 GS1 参与通过光呼吸和/或蛋白质降解释放的 NH4+ 的重新同化。
Glutamine synthetase (GS) plays a central role in plant nitrogen metabolism. Plant GS occurs as a number of isoenzymes present in either the cytosol (GS1) or chloroplast/plastid (GS2). There are several reports of improved performance in transgenic plants overexpressing GS1 transgenes driven by the constitutive CaMV35S promoter. Improvement has been attributed to the GS1 transgene product functioning to enhance re-assimilation of NH4+ released by photorespiration or protein degradation. In this paper, alfalfa and tobacco transformants expressing a soybean gene driven by a photosynthetic cell-specific promoter have been compared to transformants with the same transgene driven by the stronger CaMV35S promoter. The two classes of alfalfa and tobacco transformants showed differences in the level of GS1 transcript and GS1 protein accumulation, but the difference in the total GS activity was small. The discrepancy in the transgene expression level and GS activity has been attributed to posttranslational regulation at the level of holoprotein stability. Both classes of transformants exhibited similar level of improvement in soluble protein and in the rates of photosynthesis and photorespiration. The data supports the hypothesis that GS1 made in the mesophyll cells is involved in the re-assimilation of NH4+ released via photorespiration and/or protein degradation.
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影响因子：
4.3
作者：
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通讯作者：
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