Goyal Ravinder K, Schmidt Maria Augusta, Hynes Michael F
Lacombe Research and Development Centre, Agriculture and Agri-Food Canada, Lacombe, AB T4L 1W1, Canada.
Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, AB T2N 1N4, Canada.
Microorganisms. 2021 Jan 7;9(1):125. doi: 10.3390/microorganisms9010125.
The contribution of biological nitrogen fixation to the total N requirement of food and feed crops diminished in importance with the advent of synthetic N fertilizers, which fueled the "green revolution". Despite being environmentally unfriendly, the synthetic versions gained prominence primarily due to their low cost, and the fact that most important staple crops never evolved symbiotic associations with bacteria. In the recent past, advances in our knowledge of symbiosis and nitrogen fixation and the development and application of recombinant DNA technology have created opportunities that could help increase the share of symbiotically-driven nitrogen in global consumption. With the availability of molecular biology tools, rapid improvements in symbiotic characteristics of rhizobial strains became possible. Further, the technology allowed probing the possibility of establishing a symbiotic dialogue between rhizobia and cereals. Because the evolutionary process did not forge a symbiotic relationship with the latter, the potential of molecular manipulations has been tested to incorporate a functional mechanism of nitrogen reduction independent of microbes. In this review, we discuss various strategies applied to improve rhizobial strains for higher nitrogen fixation efficiency, more competitiveness and enhanced fitness under unfavorable environments. The challenges and progress made towards nitrogen self-sufficiency of cereals are also reviewed. An approach to integrate the genetically modified elite rhizobia strains in crop production systems is highlighted.
随着合成氮肥的出现，生物固氮对粮食和饲料作物总氮需求的贡献重要性降低，合成氮肥推动了“绿色革命”。尽管合成氮肥对环境不友好，但主要因其成本低，且大多数重要主食作物从未与细菌进化出共生关系，所以合成氮肥占据了主导地位。最近，我们在共生和固氮知识方面的进展以及重组DNA技术的发展与应用创造了一些机会，有助于增加共生驱动的氮在全球氮消费中的占比。有了分子生物学工具，根瘤菌菌株的共生特性得以快速改善。此外，该技术使得探究根瘤菌与谷物之间建立共生对话的可能性成为可能。由于进化过程未使谷物与根瘤菌形成共生关系，因此人们已测试分子操作的潜力，以纳入一种独立于微生物的氮还原功能机制。在本综述中，我们讨论了为提高根瘤菌菌株的固氮效率、竞争力以及在不利环境下的适应性而应用的各种策略。还综述了在实现谷物氮自给自足方面所面临的挑战和取得的进展。重点介绍了将转基因优良根瘤菌菌株整合到作物生产系统中的方法。
