【作者】 陆彬彬；

【导师】 张楚富；

【作者基本信息】 武汉大学 ， 生物化学与分子生物学， 2004， 硕士

【摘要】 许多因子,包括外源碳代谢物可以影响氮代谢相关酶的表达,但是关于低温对于这些酶表达的影响却鲜有报道。为了研究低温的作用,在最适温度（30℃）下生长的水稻被移栽至低温（20℃）下生长72小时,并对其碳、氮代谢的一些主要相关酶如谷氨酰胺合成酶（GS）、谷氨酸脱氢酶（GDH）、异柠檬酸脱氢酶（ICDH）活性进行了测定。研究结果表明,低温处理后,根部的GS和ICDH活性明显被诱导,与正常对照相比,二者的活性分别上升了80%和75%,也就是说,GS和ICDH之间存在正相关。Native-PAGE结合活性染色和免疫印迹分析GS同工酶及其酶蛋白表达的结果表明,GS活性的增加主要是GSrb活性和其蛋白水平上升的结果,Gsra基本保持不变。与此同时,NADH-GDH和NAD-GDH活性均下降,尽管下降幅度有所不同。生物量、NH₄⁺浓度、pH、和脯氨酸含量等一些生理指标的测定结果显示,低温下由于GS活性的诱导铵离子的吸收也得到了促进。低温促使脯氨酸含量上升了两倍,而且这种上升趋势与GS活性变化趋势是同步一致的。在添加2%的外源蔗糖条件下生长的水稻根部也发现了类似的生理现象,提示我们在调节氮代谢方面低温可能具有与碳化合物相似的效应。有趣的是,在低温和蔗糖处理的叶组织中没有发现明显可见的变化。Rubisco酶蛋白表达及叶绿素含量等相关数据表明低温对于氨同化的促进作用与光合作用效率没有直接关系。α-酮戊二酸作为一个重要的信号分子,可以调节碳、氮代谢的协同作用。这个结果有助于我们更好的了解低温对水稻氨同化的影响以及通过α-酮戊二酸介导的氨同化过程的调节。更多还原

【Abstract】 Many factors, including exogenous carbon metabolites influence the expression of enzymes involved in nitrogen metabolism, but little is known about the effect of low temperature on the expression of those enzymes. To investigate that, rice （Oryza sativa L.） seedlings grown at the optimal temperature （30℃） were subject to low temperature （20℃） stress, and several key enzymes involved in ammonium assimilation and carbon metabolism, including glutamine synthetase （GS; EC 6.3.1.2）, NADP-dependent isocitrate dehydrogenase （NADP-ICDH; EC 1.1.1.42）, and NAD（H）-dependent glutamate dehydrogenase （GDH; EC 1.4.1.2） from rice roots were assessed. It was found that at low temperature, GS and ICDH activities were increased by 80% and 75%, respectively, thus a positively parallel correlation was observed between the two enzymes. Native-PAGE analysis, together with activity staining and western blot assays, showed that both GSrb activity and GSrb protein level were enhanced under low temperature. Meanwhile, NADH-GDH and NAD-GDH activity were both reduced, though to different extent. Biomass, NH₄⁺, pH, and proline, were measured as well. At low temperature, ammonium absorption was stimulated by the elevation of GS activity. Proline content was increased 2-fold by low temperature, and this accumulation was in great agreement with the induction of GS activity. The similar phenomena were observed in the rice roots fed with sucrose, indicating that atleast partially low temperature has the similar effect as carbon compound on the modulation of nitrogen metabolism. The possibility of the regulation of this metabolic pathway by 2-oxoglurate （2-OG） was discussed.更多还原