青稞AOX与G6PDH功能及其抗逆机理研究

Mitochondria, the organ for oxidative phosphorylation and tricarboxylic acid cycle, play important roles in plant metabolism, growth and development, as well as adaptation to environmental stresses. Studies indicate that mitochondrial dysfunction lead to embryo abortion and affect photosynthesis. The alternative pathway (AP) and the pentose phosphate pathway (PPP) were increased in plant tissues suffering environmental stresses, such as senescence, pathogen, drought, saline and mechanical injury. Highland barley is a typical and most important crop in Qinghai-Tibet Plateau region. Due to its long-term adaptation to plateau environments, highland barley has higher tolerance to stresses than barley. At present, the functions and regulatory mechanism of respiratory metabolism in growth, development, and adaptation to plateau environments in highland barley are still unclear. In this project we will focus on the screening and cloning of AOX genes from highland barley; decipher the expression patterns, functions and regulation of these genes; investigate the signal transduction mechanism of AOX and G6PDH in adaptation to stresses in highland barley; resolve the relationship and mechanism among AP, PPP, and photosynthesis. For the first time, we systematically explore the action and regulatory mechanism of AP and PPP in the growth, development, and stress adaptation of highland barley. Completion of this project will contribute to understanding the mechanism of highland barley tolerance to plateau environments and will also provide the theoretical basis for molecular breeding in stress resistance and high yield in crops.

线粒体作为氧化磷酸化、三羧酸循环的位点，在植物代谢，生长发育和对环境适应中起重要作用。研究表明线粒体功能受损会导致胚胎败育，也会影响植物的光合能力；在衰老、感病、干旱、盐渍、受伤的植物组织中，交替途径（AP）和磷酸戊糖途径（PPP）均会加强。青稞是青藏高原最具特色的农作物，长期对高原环境的适应使其形成了一系列与之相适应的遗传特性，表现出比一般大麦更高的胁迫耐受性。目前对呼吸代谢在青稞生长发育及对高原环境适应的功能与调节机理知之甚少。本项目旨在筛选、克隆青稞AOX家族基因，查明其表达模式、功能与调控机理；进而探讨AOX与G6PDH在青稞逆境响应中的信号转导途径，及AP和PPP与光合作用的相互关系与作用机制，并揭示其生物学意义。该项目首次系统地探讨AP和PPP在青稞生长发育与逆境适应中的作用与调节机理，项目的完成有助于阐释青稞适应高原环境的抗逆机制，可为作物抗逆高产的分子遗传育种提供理论依据。

植物呼吸代谢的多样性是其植物对多变环境的适应性表现。磷酸戊糖途径（PPP）和交替途径（AP）广泛参与了植物生长发育和逆境适应过程。青稞是青藏高原最具特色的农作物，因长期对高原环境的适应使其表现出比一般植物更高的胁迫耐受性。目前关于呼吸代谢在青稞适应高原环境中的功能与机理仍不清楚。为此，本项目以青稞、大麦和拟南芥为材料，克隆了青稞交替氧化酶（AOX）家族基因，分析了其表达模式；探究了AP和PPP在植物生长发育与胁迫耐受中的功能及信号转导机制。主要结果显示：1. 一氧化氮 (NO)、过氧化氢（H2O2）和AP参与了青稞对Cd胁迫的耐受。AP可通过消耗过剩的还原力减少ROS产生，增强NO和H2O2保护功能；NO位于H2O2上游。2. 青稞表现出较大麦更强的盐碱胁迫耐受性。AP通过影响离子转运基因表达和质膜H+-ATPase活性，参与调节Na+区域化和外排过程，维持K/Na；外源Si通过提高G6PD活性、维持GSH稳态、改善光合作用，缓解了盐碱胁迫的抑制。3. 盐胁迫下，胞质G6PDH通过调节ASC-GSH循环关键酶提高植物的抗盐能力。4. G6PD5通过影响ABA合成和信号通路基因表达参与ABA对植物种子萌发和根生长的调节，而G6PD6不参与此过程。5. GA可通过调节G6PD5的表达影响种子中ABA和GA的平衡，进而调节种子休眠和萌发。6. 胞质G6PD功能缺失会降低胚胎发育早期相关基因表达，增加果荚和种子败育率，降低胚胎贮藏蛋白和脂肪酸含量，引起胚后发育延迟和种子产量降低。该研究可阐明植物呼吸代谢尤其是PPP和AP在植物生长发育与逆境适应中的生理功能与调节机制，为解析植物抗逆的分子机制，并可为作物抗逆高产的分子遗传育种提供理论依据。