一氧化氮对重金属和多环芳烃复合胁迫下草坪草生理特性的调控机理

The heavy metal lead (Pb) and polycyclic aromatic hydrocarbons [benzo (a) pyrene (B[a]P)] are ubiquitous in the environment, which is the representative of the inorganic and organic pollutants. Pb and B[a]P can be absorbed and accumulated easily by plants. Excess Pb and B[a]P typically causes direct or indirect inhibition of physiological processes, such as respiration, transpiration, photosynthesis, oxidative stress, cell elongation, nitrogen metabolism and mineral nutrition, resulting in growth retardation, leaf chlorosis and low biomass in plants. Lolium perenne is the most important turfgrass in north of China, and it is important of studying toxicity and mechanism of Pb-B[a]P. Pb and B[a]P can be absorbed and accumulated by Lolium perenne without obvious deleterious symptoms, which gives rise to a threat on human health by food chain. Therefore, high accumulation of Pb and B[a]P in Lolium perenne is a potential risk for both animals and human. As a crucial gaseous signaling molecule in plants, Nitric oxide (NO) plays a significant role in modulating several physiological and biochemical functions. In recent decades, an increasing number of articles have reported the effect of exogenous NO in alleviating heavy metal and PAHs toxicity in different plants, although the physiological processes and mechanisms of NO in alleviating heavy metal and PAHs toxicity are still far from clear. Therefore, it is necessary and meaningful to investigate the mechanisms of NO in alleviating Pb and B[a]P toxicity in Lolium perenne, it will also provide significant theory basis to control the accumulation of Pb and B[a]P in Lolium perenne seeds. Lolium perenne will be used in the project, a pot culture experiment is conducted to investigate the effect of exogenous sodium nitroprusside (SNP), a NO donor, on alleviating the toxicity of Pb-B[a]P to Lolium perenne. In order to elucidate the mechanisms of mitigate effect of NO application on Pb-B[a]P toxicity, growth parameters, reactive oxygen species, photosynthesis and proteomics were researched.

环境中的污染物正趋于多元化和复杂化，主要以无机和有机污染物——重金属和多环芳烃的复合形式存在，严重威胁环境和人类健康。铅(Pb)和苯并(a)芘(B[a]P)是环境中普遍存在的具有代表性的重金属和多环芳烃污染物。一氧化氮(nitricoxide，NO)是一种在植物抵抗逆境过程中发挥重要作用的信号分子，但是国内外对NO如何调控Pb-B[a]P复合胁迫下植物的生理机制研究还不清楚。黑麦草(Lolium perenne L.)是一种重要的草坪草，对土壤Pb和B[a]P有较好的富集和吸收能力。本项目以Pb-B[a]P复合胁迫下黑麦草为材料，分析内源NO在胁迫响应中的代谢规律，同时施加外源NO，探讨NO对Pb-B[a]P复合胁迫下黑麦草抗氧化系统、光合荧光特性、特异蛋白表达的生理影响，较系统地研究NO对Pb-B[a]P复合胁迫下黑麦草生理特性的调控机理，为植物修复重金属和有机污染物技术提供理论依据。

一氧化氮（NO）作为植物体内一种重要的信号分子，对缓解生物胁迫与非生物胁迫有着明显的作用。探究NO参与Pb和B[a]P复合胁迫下黑麦草应答机制及生理调控作用，拓宽外源物质调控植物逆境生理胁迫的研究思路，旨在通过利用植物修复来治理土壤中重金属和多环芳烃的复合污染具有重要的理论和实践意义。低浓度Pb和B[a]P复合胁迫对黑麦草种子萌发、幼苗生长有一定促进作用，高浓度Pb和B[a]P复合胁迫则抑制黑麦草叶片光合色素合成，影响其光合参数和叶绿素荧光特性，从而抑制植株生长。施加一定浓度的外源NO后，随着NO浓度的上升，光合色素、渗透物质、抗氧化酶以及MDA和GSH等含量呈现上升趋势。适宜浓度的SNP对黑麦草Pb和B[a]P复合胁迫下MDA含量、光合色素含量、Pn、Gs、Ci和Fv/Fm的调控作用最好。NO与黑麦草的各项指标的回归分析中，相关性最大的依次为NR、SOD、GSH和CAT，说明抗氧化酶与外源NO的相关性最为密切。本研究表明适宜浓度的NO在Pb和B[a]P复合胁迫下对黑麦草生长发育有缓解作用，但高浓度NO对黑麦草生长发育存在明显的胁迫作用。NO对植物的生长和发育具有调控作用，能够提高植物叶片中抗氧化酶的活性，消除自由基，从而缓解Pb和B[a]P复合胁迫造成的细胞膜脂过氧化损伤，硝酸还原酶途径是黑麦草应答Pb和B[a]P复合胁迫产生NO的主要途径。同时NO可以调节差异性蛋白质表达，这些差异表达蛋白质主要参与植物体内氨基酸和蛋白质代谢、光合作用、渗透物质代谢、抗氧化酶代谢等重要生物学过程。基于以上结果，我们推测外源NO重新分配蛋白的降解、折叠与合成，促进光合作用和能量代谢，激活抗氧化酶还原机制，修饰细胞壁结构，丰富转录水平，从而清除非功能损伤蛋白，维持蛋白的正常折叠，推动新的蛋白合成，降低细胞氧化伤害，确保能量补给和渗透平衡，最终提高黑麦草对Pb和B[a]P复合胁迫的抗逆性。我们后续仍然会集中在NO调节Pb和B[a]P复合胁迫下蛋白组学和相关抗逆基因表达的研究。