一氧化氮调控红树植物白骨壤盐腺泌盐的分子机制研究

Nitric oxide (NO), as a multifunctional bioactive molecule, is involved in plant growth and development, as well as the resistant responses to various environmental stresses. Previous studies have reported that NO remarkably enhanced the salt tolerance in halophytes. Salt secretion by specific glands represents an avoidance strategy that permits the regulation of intracellular ionic homeostasis in some halophytes. Our previous studies indicated that NO played an important role in modulating the salt secretion by salt glands of a salt-secreting mangrove plant, Avicennia marina. While the detailed molecular mechanisms of NO-modulated salt secretion is not very clear yet. In this project, we first analyze the effects of NO on salt secretion in salt glands of A. marina at the physiological level, then further reveal the relationships between salt secretion and ion transport proteins. Secondly, we try to study the effects of NO produced by different NO biosynthesis pathways on development of salt glands and salt secretion using the inhibitors of NO synthesis. For further clarify the molecular mechanism of NO-modulated salt secretion of salt glands, the salt gland cells will be separated and collected by laser capture microdissection technique. Some critical proteins and genes, whose expression levels are significantly changed under high NO level, will be identified by comparative proteomic analysis and whole transcriptome analysis. The roles of these proteins and genes in salt secretion will be analyzed in further study. All of these results will taken together to explain the molecular mechanisms and regulatory network responsible for NO-modulated salt secretion in salt glands, which will help us to reveal the mechanisms of salt tolerance in salt-secreting plant and find some critical genes involved in plant salt tolerance.

一氧化氮（nitric oxide，NO）作为一种多功能的信号分子广泛参与植物的生长发育过程并可对多种环境胁迫做出应答。已有研究表明NO可显著提高盐生植物的耐盐性。盐腺作为泌盐盐生植物最显著的形态结构，在调节离子平衡，提高植物耐盐性等方面发挥重要作用。我们前期研究结果表明，NO可调控泌盐红树植物白骨壤盐腺的泌盐，但其分子机制仍不清楚。本项目首先在生理水平深入分析NO对白骨壤盐腺泌盐的调控作用，揭示与离子转运蛋白的关系；其次，利用特异性NO产生抑制剂研究不同NO产生途径对白骨壤盐腺发育及盐腺泌盐的不同影响。在分子机制的研究方面，我们利用激光捕获显微切割技术分离纯化盐腺细胞，结合差异蛋白质组学和高通量转录组测序技术，寻找盐腺细胞中对NO明显响应的蛋白和基因，并分析其在泌盐中的作用。本项目对探索NO调控白骨壤盐腺泌盐的分子机制及信号网络，发掘关键耐盐基因，揭示泌盐红树植物的耐盐机制具有重要意义。

土壤盐渍化是人类面临的严重生态危机之一，日益威胁着人类赖以生存的土地资源，对盐生植物的耐盐机理的研究尤为重要。一氧化氮（nitric oxide，NO）作为一种多功能的信号分子广泛参与植物的生长发育过程并可对多种环境胁迫做出应答。已有研究表明NO可显著提高盐生植物的耐盐性，而对其内在机制却知之甚少。本项目选择典型泌盐红树植物白骨壤为研究对象，利用2-DE和iTRAQ差异蛋白组学系统研究一氧化氮调控白骨壤泌盐的分子机制。叶片蛋白组学研究发现：盐胁迫条件下，mRNA的转录和蛋白的合成受到抑制，其中CSP41A在叶绿体中起到重要的调控作用, 而HSP蛋白作为分子伴侣来保证蛋白的正确折叠；NO通过调节转录因子的表达来提高白骨壤的抗盐能力。盐胁迫条件下，白骨壤光合能力的下降是由于非气孔因素造成的，主要原因是由于与暗反应相关的蛋白的降解。而NO则通过提高与叶绿体合成相关的蛋白的表达来部分恢复光合作用。盐胁迫降低了白骨壤能量代谢和初级产物代谢从而引起植物生长缓慢，而NO在到一定程度上恢复白骨壤的能力代谢及初级产物合成。通过对白骨壤叶片上表皮进行蛋白提取并做同位素标记进行高通量色谱扫描后发现，盐胁迫会刺激植物体内囊泡的产生和运输，使体内多余的盐离子在液泡内富集，并通过囊泡运输的方式，将液泡内富集的钠离子排除体外，从而达到泌盐的效果。本研究对阐明NO调控植物盐腺泌盐的信号网络、揭示 NO 调控的盐生植物的耐盐机制、在未来利用基因工程手段培育耐盐植物等方面均具有重要意义。