解偶联蛋白在植物逆境响应中的功能及与交替途径的相互作用机理研究

Mitochondria, as the main site of energy produce, play essential roles in plant development and adaptation to environmental stresses. Uncoupling pathway mediated by plant mitochondrial uncoupling protein (PUMP) and alternative pathway mediated by alternative oxidase (AOX) are two energy dissipation systems in mitochondrial inner membrane. PUMP and AOX play similar functions like decreasing ATP production, maintaining energy balance, and participating stress defense. Although numerous studies on the structure and function of PUMP and AOX have been reported, the interaction and signal transduction mechanism of PUMP and AOX in energy metabolism as well as stress defense of plants are rarely reported. Moreover, the functions and regulative mechanism of PUMP families are still unclear. Therefore, this project will screen T-DNA mutants and over-expression plants of PUMP and AOX, and carry out the following research from the view point of physiology and molecular genetics: 1. The functions and signal transduction mechanism of PUMP in plant adaptation to environmental stresses; 2. Interaction and molecular mechanism of PUMP and AOX in energy metabolism and stress defense of plants. This project would clarify the functions and interaction of PUMP and AOX in energy metabolism and stress adaptation of plants, and provide the theoretical basis for the molecular genetic breeding in stress resistance and high yield of crops.

线粒体作为细胞的供能场所，在植物发育与逆境适应中起关键作用。植物解偶联蛋白（PUMP）介导的解偶联途径和交替氧化酶（AOX）介导的交替途径是线粒体内膜上的能量耗散系统。PUMP和AOX有相似的功能：减少ATP生成，维持能量平衡，参与逆境防御。目前，PUMP和AOX的研究主要集中在结构与功能方面，但关于PUMP和AOX在植物能量代谢与逆境防御中相互作用与信号转导机制鲜有报道；并且对PUMP家族成员的功能与调控机理仍不清楚。据此，本项目拟通过筛选和构建拟南芥PUMP与AOX家族各基因缺失突变体与超表达植株，从生理学与分子遗传学角度重点研究：1. PUMP参与植物逆境防御的功能与分子机理，查明其信号转导机制；2. PUMP与AOX在植物能量代谢与逆境防御中的相互作用与调节机制。该项目可阐明PUMP与AOX在植物能量代谢与逆境适应中的功能与相互作用关系，并为作物抗逆高产的分子遗传育种提供理论依据。

线粒体在植物发育与逆境适应中起关键作用。植物线粒体内膜除了细胞色素主路途径，还存在多条能量耗散系统，其中交替氧化酶（AOX）介导的交替途径和解偶联蛋白（PUMP/UCP）介导的解偶联途径是主要的能量耗散途径。研究发现UCP和AOX可维持细胞能量平衡，参与逆境防御；但关于其分子机制仍知之甚少。据此，我们构建并筛选了拟南芥PUMP/UCP与AOX家族基因缺失突变体、GUS标记系、超表达系和回补系；通过杂交获得了多种双突和三突变体；明确了其表达模式；并探讨了他们在植物逆境适应与生长发育中的功能与相互关系。主要结果发现：a. UCP1和AOX1a参与调节氮的同化、碳代谢、C/N比率等影响拟南芥低氮胁迫耐受，并最终影响种子产量；与AOX1a相比，UCP1在此过程中发挥更重要功能。b.干旱胁迫下，UCP1和AOX1a功能缺失会显著降低拟南芥干旱胁迫耐受性，增加叶绿体蛋白羰基化程度，降低叶绿体蛋白稳定性，降低光合能力；在此过程中，UCP1和AOX1a起着协同作用。c. AOX和UCP通过影响ABA信号通路的下游转录因子ABI3、ABI4和ABI5参与对种子萌发的调节。d. 盐胁迫下，MKK9-MAPK3/MAPK6通路在转录、翻译和翻译后水平参与对拟南芥AOX的调节，最终增强交替途径的容量。e. 镉胁迫下，交替途径通过调节细胞内的氧化还原状态，有效缓解氧化损伤，提高Cd胁迫耐受性。e. 呼吸代谢的葡萄糖支路途径-磷酸戊糖途径关键酶Cyt-G6PD是维持干旱胁迫下大豆根系氧化还原平衡所必需的，而H2O2依赖的NO信号途径参与了对这一过程的调节；Cyt-G6PD负调控盐胁迫对拟南芥主根分生区和伸长区的抑制，参与ABA对种子萌发和根生长的调节。上述研究可增加我们对呼吸代谢在植物发育与逆境适应中的功能与调控机理的认识，并为作物抗逆高产的分子遗传育种提供理论依据。