【作者】 周忠新；

【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， 2005， 硕士

【摘要】 糖、有机酸以及氨基酸影响碳-氮代谢过程中的相关酶的基因表达和活性。将蔗糖分别加入到含有相同氮素浓度的（NH₄）₂SO₄（NH₄⁺）或丙氨酸（Ala）作为氮源的营养液中培养水稻,测定幼苗根的谷氨酰胺合成酶（GS）、依赖于NADH的谷氨酸合酶（NADH-GOGAT）、磷酸烯醇式丙酮酸羧化酶（PEPC）、依赖于NADP的异柠檬酸脱氢酶（NADP-ICDH）和依赖于NADH的谷氨酸脱氢酶（NADH-GDH）的活性。结果显示,蔗糖诱导生长在NH₄⁺氮源中的幼苗根的GS、NADH-GOGAT活性,抑制Ala氮源中的幼苗根的这两种酶活性,蔗糖对PEPC、NADP-ICDH和NADH-GDH活性的影响也不同;未加蔗糖时,以Ala作为氮源的幼苗根的GS、NADH-GOGAT以及PEPC和NADP-ICDH的活性明显高于以NH₄⁺为氮源时的活性;生物量和蛋白质水平的变化与上述参数的变化基本一致。给生长在（NH₄）₂SO₄作氮源的营养液中的水稻添加不同浓度的蔗糖,结果显示:从24小时到48小时,GS、NADH-GOGAT、NADP-ICDH活力、生物量和蛋白含量都逐渐增加,也都同加入的蔗糖浓度呈正相关性;到72小时的时候,GS活力在蔗糖浓度为0.5%和2%时有所下降,但当蔗糖浓度为0.1%时继续上升。NADH-GOGAT活力在蔗糖浓度为0.5%和0.1%时仍然继续上升,只是在蔗糖浓度为2%时表现出下降。NADP-ICDH、生物量和蛋白含量在每种糖浓度都持续增加。NADH-GDH在每种糖浓度条件下的三个时间点都持续下降。NADH-PEPC在糖浓度为0.1%时从24小时到72小时持续增加,在糖浓度为0.5%和2%时,在72小时有所下降。基于Ala碳骨架的存在,这些结果表明,碳/氮平衡是影响这些酶活性差别表达的主要原因。更多还原

【Abstract】 Sugar, organic acid and amino acids have important effects on gene expression and enzyme activities involved in carbon and nitrogen metabolism. With rice cultivating, sucrose was fed to the nutrient solution containing （NH₄）₂SO₄ （NH₄⁺） or L-Ala, and then determined the activities of glutamine synthetase（GS）, NADH-dependent glutamate synthase（NADH-GOGAT）, phosphoenolpyruvate carboxylase（PEPC）, NADP-dependent isocitrate dehydrogenase（NADP-ICDH）, and NADH-dependent glutamate dehydrogenase（NADH-GDH）. The results showed that sucrose induced markedly the enzyme activities of GS and NADH-GOGAT in roots of seedlings with NH₄⁺ as the nitrogen source ,however, inhibited them in roots of seedlings growing in L-Ala nitrogen source. Sucrose had different effects on the activity changes of PEPC, NADH-ICDH and NADH-GDH. Without sucrose supplementation, the activities of GS, NADH-GOGAT, PEPC, NADP-ICDH in the roots of rice seedlings growing in L-Ala nitrogen source were higher than that with NH₄⁺ as the nitrogen source. The changes trend in biomass and protein content were coincident with the former parameters. Different concentration sucrose was fed to the seedlings grown in （NH₄）SO₄ nutrient solution, the results followed. From 24h to 48h, the activity of GS, NADH-GOGAT, NADP-ICDH, the soluble protein content and biomass increased gradually, and their values have a positive correlation with sucrose concentration; to 72h, the enzyme activity of GS began to fall down when the sucrose concentration was 0.5% and 2%, but continued to increase when the sucrose concentration was 0.1%. The enzyme activity of NADH-GOGAT maintained to increase when the sucrose concentration was 0.1% and 0.5%, only decreased when the sucrose concentration was 2%. The enzyme activity of NADP-ICDH, biomass and the soluble protein content continued to increase under three different sucrose concentration. The enzyme activity of NADH-GDH maintained to decrease at three sampled time at every sucrose concentration. For NADH-PEPc, the enzyme activity maintained to increase from 24h to 72h when the sucrose concentration was 0.1%, had a decrease at 72h when the concentration was 0.5% and 2%. Based on the additional carbon skeleton of Ala compared to （NH₄）SO₄, these resulted suggested that carbon/nitrogen balance play a important role in the different regulation of the enzyme activity.更多还原