玉米中两种谷氨酸脱氢酶同工酶在不同温度胁迫下的功能与机制研究

Both heat stress and cold stress can cause excessive accumulation of ammonium ion in plant cells, and thus cause toxicity to plants. Glutamate dehydrogenase (GDH) can remove the excessive ammonium ion in the cell, and then reduce the toxicity of ammonium ion. There are two glutamate dehydrogenase isoenzymes in maize(ZmGDH1 and ZmGDH2). However, the function and mechanism of these ZmGDH isoenzymes in maize under different temperature stress remain unknown. Preliminary studies showed that, ZmGDH1 plays a role in heat stress, while ZmGDH2 plays a role in cold stress. The amino acids composition of the hinge region in the dimensional structure determine the different temperature adaptabilities of them. This project intends to perform further studies on the function and mechanism of these ZmGDH isoenzymes under heat stress and cold stress systematically, through series of in vivo and in vitro assays, and finally establish the work model which maize resists heat temperature stress by ZmGDH1, and resists cold temperature stress by ZmGDH2. This project will provide evidence for elucidating the function and mechanism of these ZmGDH isoenzymes under different temperature stress, provide new ideas for exploring the effects caused by different temperature stress in maize, and provide basis for understanding the tolerance mode of maize under different temperature stress.

高温胁迫与低温胁迫都会引起植物细胞内铵根离子的过量积累，进而对植物造成毒害。谷氨酸脱氢酶（GDH）可以清除细胞中过量的铵根离子，从而降低其对细胞的毒害作用。玉米含有两种谷氨酸脱氢酶同工酶（ZmGDH1和ZmGDH2）。然而，这两种ZmGDH同工酶在不同温度胁迫下的功能和机制依然未知。初步的研究表明，ZmGDH1在高温胁迫中发挥作用，而ZmGDH2在低温胁迫中发挥作用。两者三维结构铰链区的氨基酸构成决定了其不同的温度适应性。本项目拟通过一系列的体内、外实验，进一步系统地研究玉米的两种ZmGDH同工酶在高温胁迫和低温胁迫下的功能与机制，最终确立玉米通过ZmGDH1抵抗高温胁迫，通过ZmGDH2抵抗低温胁迫的工作模式。本项目可为阐明玉米中两种ZmGDH同工酶在不同温度胁迫下的功能与机制提供依据，为探索不同温度胁迫对玉米造成的影响开辟思路，并为理解玉米在不同温度胁迫下的抗逆方式奠定基础。

近年来，随着气候环境的不断变化，高温胁迫与低温胁迫都对我国农作物产量造成影响。阐明作物耐受不同温度胁迫的分子机制，可为因地制宜的分子育种提供理论依据。本项目结合生物化学、分子生物学、计算生物学、植物学等学科研究方法，系统地研究了玉米谷氨酸脱氢酶同工酶ZmGDH1与ZmGDH2在不同温度胁迫中的作用与机制。首先，通过对谷氨酸脱氢酶结构的重新修订，项目团队发现了谷氨酸脱氢酶铵根离子底物抑制的分子机制，并给出了底物抑制的统计力学解释；其次，项目按照计划阐明了玉米通过ZmGDH1耐受高温胁迫，而通过ZmGDH2耐受低温胁迫的作用机理，并发现ZmGDH1与ZmGDH2蛋白质铰链区的柔性是影响两者温度适应性的关键；最后，通过分子进化分析，推断出两种同工酶的进化可能是侏罗纪至白垩纪之间的气候波动造成的。该研究从理论上阐明了同工酶对于植物适应不同温度胁迫的重要性，并为不同纬度、不同区域的分子设计育种奠定了基础。