关键词: 生物固氮, 合成生物学, 固氮酶, 非豆科作物, 自主固氮作物

Abstract:

Nitrogen is an essential element for plant growth and development. Legume plants form symbiotic relationships with rhizobia, which facilitates the biological fixation of atmospheric nitrogen (N₂) into ammonia (NH₃) that is directly usable by the plants through the action of rhizobial nitrogenase. This process reduces the need for chemical nitrogen fertilizers. However, under the pressure of continuously increasing food demand driven by a growing global population, the major non-leguminous food crops for humans, such as maize, rice and wheat, lack the ability to form nodules and establish symbiosis with rhizobia. This results in a heavy dependence on chemical nitrogen fertilizer to maintain high and stable yields. However, the overuse of chemical nitrogen fertilizers has caused serious environmental problems, including soil compaction and acidification, greenhouse gas emissions, and water eutrophication, all of which threaten agricultural sustainability and global food security. To achieve green and sustainable agricultural development and reduce the use of chemical fertilizers, nitrogen-fixing synthetic biology utilizes tools of synthetic biology to modify, optimize, and even de novo design biological nitrogen fixation systems. These engineered systems are applied across agricultural production, environmental protection, and industrial biotechnology, addressing global challenges such as excessive dependence on chemical nitrogen fertilizers, high energy consumption, and environmental pollution. The innovative strategies for bioengineering biological nitrogen fixation in non-leguminous crops can be categorized into the following four aspects. These strategies include engineering rhizobial nitrogen-fixing bacteria to increase nitrogen supply to the host, engineering crops to enhance the ability of plants to recruit nitrogen-fixing microbes in the rhizosphere to improve nitrogen use efficiency, forming nodule-like structures for symbiotic nitrogen fixation, and transferring functional nitrogenase components into plant cells to create self-fertilizing crops. Significant advances have been achieved in all these approaches in recent years, demonstrating their potential to boost yields while reducing fertilizers. This review provides a comprehensive overview of recent breakthroughs in nitrogen-fixing synthetic biology. We also discuss the current challenges and future prospects, offering theoretical insights and technical guidance to support further research and the practical application of biological nitrogen fixation in sustainable agriculture and environmental protection.

Key words: biological nitrogen fixation, synthetic biology, nitrogenase, non-leguminous crops, self-fertilizing crops