一氧化氮对盐胁迫下烟草细胞渗透调节能力的影响

Effects of Nitric Oxide on Osmoregulation of Tobacco Cells under Salt Stress

一氧化氮(NO)作为信号分子广泛参与植物的生长发育、逆境胁迫响应过程。为了明确NO对细胞渗透调节作用,该研究以NaCl为盐胁迫因子,以烟草悬浮细胞为材料,研究了NO对盐胁迫下细胞渗透调节能力的影响。结果显示:(1)NaCl胁迫能诱发烟草细胞内源NO的生成,且100mmol·L-1 NaCl诱发了细胞内源NO的快速产生,在1h达到峰值,NO产生量约为对照的2倍,之后NO产生量快速下降,直至3h才逐渐回升,并在48h内维持在较高水平。(2)外源NO显著增强了烟草细胞的抗渗透胁迫能力,且150μmol·L-1 NO供体硝普钠(SNP)处理显著提高了NaCl胁迫下细胞的活力和再生能力(提高幅度分别为78.6%和63.2%),降低了细胞死亡率(降幅约为48.5%);SNP处理下的NaCl胁迫细胞能更大程度降低渗透势,延缓水势的降低,维持细胞压力势。(3)外源NO显著促进了NaCl胁迫细胞中脯氨酸的合成和积累,且150μmol·L-1 SNP处理将NaCl胁迫细胞中的脯氨酸含量提高25.9%;SNP处理也影响了脯氨酸代谢关键酶的活性和基因表达水平,即提高了谷氨酸脱氢酶(GDH)、精氨酸酶和鸟氨酸转氨酶(OAT)的活性,降低了脯氨酸脱氢酶(PDH)的活性,同时使GDH、OAT和PDH基因的表达表现出与酶活性相似的变化趋势。研究表明,NO参与了盐胁迫下烟草细胞的渗透调节,通过调控脯氨酸代谢可能是NO参与渗透调节的重要机制。

As universal signaling properties,NO（nitric oxide）involves not only in plant growth and development,but also in plant response to abiotic and biotic stress.Until now,its function of osmoregulation is un-known.The study,using NaCl as a stress factor and tobacco suspension cells as experimental material,we investigated the effects of NO on osmoregulation of tobacco cells under NaCl stress.The results showed that：（1）Endogenous NO of tobacco cells was induced by NaCl stress.During 100mmol·L-1 NaCl stress,production of NO was rapidly induced in cultured cells in vivo,and reached at the peak（with 2times of the control）in 1hafter the stress treatment,then the production was deduced rapidly until 3h,from then on,the amount of NO was increased gradually and maintained at a high level until 48 h.（2）Exogenous NO significantly enhanced osmotic stress tolerance ability of tobacco cells.150μmol·L-1 NO donor sodium nitroprusside（SNP）significantly improved vitality and regrowth of the cells by 78.6%and 63.2%,respectively,lowered cell death by 48.5%,when compared to that of non SNP treatments tress cells.Further study indicated that SNP treatments led to relatively lower cell solute potential and higher water potential,which was benefit for maintaining cell pressure potential under the stress.（3）Exogenous NO significantly improved the synthesis and accumulation of proline in tobacco cells under NaCl stress.150μmol·L-1 SNP increased proline accumulation of the cells by 25.9%due to effecting the activity of proline metabolic key enzymes,including the activation of glutamate dehydrogenase（GDH）,arginase and ornithine aminotransferase（OAT）,and the inhibition of proline dehydrogenase（PDH）.Meanwhile,SNP also had corresponding effects on the expression of GDH,OATand PDHgenes.Our results suggest that NO involved in osmotic adjustment of tobacco cells to enhance salty tolerance,in which NO regulated proline metabolism of the cells was an important mechanism.