Abstract: Haidao 86 is a rice variety, which originally grew on coastal beaches and showed high resistance to alkali stress. In this paper, the difference in nitrogen metabolism of Haidao 86 and an alkali sensitive variety Zhenshan 97 under alkali stress was studied to find out the physiological and molecular bases for the high alkali resistance of Haidao 86. The rice seedlings were treated with salt solution at pH 9.0, then the contents of nitrogen-containing substances, the activity of nitrogen assimilation enzymes and the expressions of related genes were examined. The results displayed that alkali stress caused less decreases in contents of NO₃^- and soluble protein in Haidao 86 than those in Zhenshan 97, but induced higher accumulation of NH₄⁺in Zhenshan 97. For Haidao 86 under alkali stress, the NR activity in roots as well as GS activities in roots and leaves showed no significant difference, the NR activity in leaves as well as GOGAT activities in roots decreased, while the GOGAT activity in leaves increased when compared with those under control. The activities of NR, GS and GOGAT in Zhenshan 97 all decreased significantly under alkali stress, and the extent of reduction was greater than those of Haidao 86. Alkali stress had no significant effect on the activity of glutamate dehydrogenases (GDH) in Haidao 86, but induced a significant increase in that of Zhenshan 97. Analysis of relative transcript levels of nitrogen metabolism genes using qRT-PCR displayed, that, under alkali stress, the expression pattern of NR and GDH genes in Haidao 86 and Zhenshan 97 were consistent with the change of enzyme activities, while the expression of NADH-GOGAT genes were different from the change of enzyme activities, the expression of OsNADH-GOGAT1 and NADH-GOGAT2 was significantly increased, the transcript levels of NR and GOGAT genes in Haidao 86 were higher than those in Zhenshan 97, on the contrary, transcript levels of GDH genes in Haidao 86 were lower than those in Zhenshan 97. Summarily, the high alkali stress resistance of Haidao 86 is related to its stable activities of enzymes in nitrogen metabolism, the results provide an important theoretical basis for further understanding the mechanism of salt tolerance of rice and breeding salt tolerant rice varieties.

Key words: Raidao 86, alkaline stress, nitrogen metabolism, gene expression

摘要： 海稻86是原生长于沿海滩涂的水稻品种,具有强耐碱性。为探究海稻86耐碱胁迫的生理和分子机制,本研究以海稻86和对碱敏感的水稻品种珍汕97为材料,采用pH值9.0的碱处理液处理水稻幼苗,并检测其根和叶中含氮物质含量、氮代谢相关酶活性和基因表达量。结果表明,碱胁迫下,海稻86根和叶中硝态氮和可溶性蛋白含量降幅低于珍汕97,而珍汕97根中氨态氮的积累量显著大于海稻86。碱胁迫下,海稻86根部硝酸还原酶(NR)活性以及根和叶片谷氨酰胺合成酶(GS)活性与非胁迫下对照(CK)相比均无显著变化,叶片NR活性以及根部谷氨酸合成酶(GOGAT)活性降低,叶片GOGAT活性升高;珍汕97根和叶片NR和GS以及根部GOGA活性均显著降低,降幅明显大于海稻86;碱胁迫对海稻86的GDH活性无显著影响,但珍汕97的GDH活性显著升高。此外,碱胁迫下,海稻86和珍汕97的NR以及GDH基因表达量与酶活性变化较一致,NADH-GOGAT基因表达变化与酶活性变化存在差异,OsNADH-GOGAT1和NADH-GOGAT2表达量显著升高,海稻86的NR和GOGAT基因表达量高于珍汕97,GDH基因表达量低于珍汕97。综上表明海稻86具有强耐碱胁迫能力,与其具有较稳定的氮代谢关键酶活性有关。本研究为深入了解水稻耐碱机理和培育耐碱水稻品种提供了重要的理论依据。

关键词: 海稻86, 碱胁迫, 氮代谢, 基因表达