盐胁迫下活性氧介导植物根生长作用机理研究

The northwest of China is the major salint-alkaline desert soil regions, which is one of the most serious environmental stresses impeding plant growth and limiting crop production. Stress conditions are known to induce rapid and increased generation of reactive oxygen species (ROS) including hydrogen peroxide (H2O2), which may lead to oxidative damage on plant cells. On the other hand, ROS as a signal molecule is involved in growth and developmental process as well as various physiological and biochemical responses in plants. And also, the determination of plant adaptation to different stress conditions is important to ecological reconstruction in the salint-alkaline desert of northwest china. Plant root systems are quite susceptible to different stress conditions. As an important organ, plant root not only possesses many important physiological functions including absorption, fixation, storage, synthesis, and reproduction, but also influences the plant's adaptation to the environment. However, little information is known about regulation mechanism of ROS generation on the root growth of desert halophytes under stress environments. L. aureum (L.) Hill is a typical desert halophyte with the strong ability to resist salinity and alkalinity, drought, wind and dust, and it can efficiently fix moving sands. Drought-tolerant Xihan 2 is a wheat species widely grown in the north-west of China. In this study, these species are used to investigate the relationship of ROS generation and root growth, to comprehensively analyze the changes of enzyme activity, protein content and gene expression involved in ROS production, and thus to determine the regulation function of ROS on root growth under stress conditions, through a number of control experiments combined with protein electrophoresis, organization/cell chemistry orientation method and fluorescence microscopy. On the basis of these analyses, further study mainly aims to evaluate the effects of ROS generation on the structure and components of cell wall in plant roots, and to explore endogenous signal molecules associated with ROS actions, and thus to reveal the regulation approach and mechanism of ROS on plant root growth. These studies aim to provide scientific basis and theoretical guidance for further investigating the roles and the regulation mechanism of ROS signaling as well as for carrying out molecular genetic manipulation.

活性氧（ROS）作为胁迫因子或信号分子参与植物生长发育和生理生态过程的调控，但如何介导盐胁迫下植物根生长作用的调控机理目前尚不清楚。本项目拟以西北荒漠盐生植物补血草和耐盐小麦等为材料，采用生理生态检测法结合蛋白电泳、组织/细胞化学定位法和荧光技术等手段，研究盐胁迫下ROS的产生与植物根生长发育的相关性，综合分析组织细胞ROS产生相关酶活性、蛋白量及基因表达的变化，进而确定ROS对根生长过程的调控作用；在此基础上，本项目将重点分析ROS产生对根细胞壁结构成分的影响，发掘涉及ROS作用的其它内源性信号分子，揭示ROS作用可能的调控途径及调控机制。这些研究旨在为进一步深入研究植物ROS信号分子作用及调控机制并进行分子遗传操作提供重要的科学依据和理论指导。

高盐、重金属等环境因子严重影响着植物的生长发育，限制着生态建设和农业可持续发展。本研究在国家自然科学基金(NO 31360094)的资助下，选取具有生态价值和经济价值的西北盐生植物黄花补血草和西北大面积种植的小麦等植物为材料，开展了植物幼苗和愈伤组织对盐胁迫及重金属胁迫的生理生态响应等方面的工作，研究发现：(1) 盐胁迫诱导了黄花补血草幼苗叶片的抗氧化反应，使H2O2和•OH产生增加，抗氧化酶和多胺代谢酶活性增强，非酶抗氧化物质含量提高，使幼苗清除活性氧的能力增强，表现出对盐环境的适应性；(2) 盐胁迫可能通过与胞外H2O2产生相关的途径诱导了细胞活力的丧失，导致干旱耐受型小麦“宁春”和干旱敏感型小麦“西旱”根生长的抑制，且干旱耐受型“宁春”根中H2O2积累的增加可能是由POD和GR活性的降低以及细胞壁POD和DAO活性的升高引起的，而APX和GR的抑制以及SOD和DAO活性的增强与干旱敏感型“西旱”根中H2O2含量的增加有关；(3) 小麦幼苗根叶中内源性NO和胞间ROS的产生相互影响，特别是 NO和胞间ROS影响总ROS代谢和抗氧化酶活性，导致小麦根和叶表现出不同的抗氧化反应；盐胁迫下小麦根质外体ROS及NO的积累也相互影响, 可能共同调控植物在盐胁迫响应过程中根对Na、K和Ca的吸收及其向地上部分的转运；(4) Zn胁迫对小麦根生长的抑制是H2O2和NO相互作用的结果，胞外ROS的减少和内源NO的增加可能导致了Zn + DPI处理对小麦根生长的显著抑制；(5) 不同的锌、铁和铜复合胁迫对小麦幼苗锌、铁、铜元素的吸收及根系生长表现协同作用和显著的抑制作用，且Zn + Fe + Cu处理的抑制作用最明显；此外，在不同的Zn、Fe和Cu复合处理下，每个抗氧化酶包括总的和质外体的SOD、POD、CAT、APX和GR表现出特异性反应，其中 GR、SOD和APX等作为重要保护机制来对抗氧化损伤；(6) NO的积累对于外源AsA诱导的Cd耐受性和内源性AsA的产生是需要的，NO信号传导途径介导了外源AsA诱导的内源性AsA产生，二者共同作用导致小麦对Cd胁迫的耐受性；(7) Zn可以缓解铁对根系生长的抑制作用，这可能与脂质过氧化的减少、细胞存活率的增加和活性氧产生的减少有关。这些研究旨在揭示植物适应盐渍化等非生物胁迫的生理生态机制，为合理开发利用独特的植物资源、西北荒漠盐碱区