Jiang Shanshan, Li Jiang, Wang Qingyu, Yin Changyan, Zhan Yuhua, Yan Yongliang, Lin Min, Ke Xiubin
Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu 610041, China.
Microorganisms. 2022 Oct 7;10(10):1986. doi: 10.3390/microorganisms10101986.
Diazotroph mutants designed using metabolic engineering to excrete surplus ammonium were used to enhance nitrogen fixation and plant growth, as the levels of nitrogen fixation attained with diazotrophs are insufficient for the plant's needs. In this study, wild-type (A1501) and engineered ammonium-excreting (1568/pVA3) strains of nitrogen-fixing strains were tested in vitro based on plant growth-promoting traits, such as phosphate solubilization ability, indole acetic acid (IAA) production and nitrogenase activities, as well as ammonium excretion as affected by mannitol-mediated osmotic stress. The maize plant growth-promoting effect of the A1501 and 1568/pVA3 strains was evaluated in pots and in the field, and the N-dilution technique was employed to assess the proportion of plant nitrogen derived from nitrogen fixation. The results demonstrate that the 1568/pVA3 strain displayed higher IAA production and nitrogenase activity than A1501 and released significant quantities of ammonium. After 50 days, in all of the conditions assayed, maize inoculated with 1568/pVA3 accumulated more plant biomass (3.3% on average) and fixed N (39.4% on average) than plants inoculated with A1501. In the field experiment, the grain yield of maize was enhanced by 5.6% or 5.9% due to the inoculation of seeds with 1568/pVA3 in the absence or presence of exogenous N fertilizer, respectively. Therefore, the engineered strain tested in the greenhouse and field was shown to perform better than the wild-type strain with respect to maize growth parameters and biologically fixed nitrogen.
利用代谢工程设计的能分泌多余铵的固氮菌突变体，用于提高固氮作用和植物生长，因为固氮菌实现的固氮水平不足以满足植物需求。在本研究中，基于促进植物生长的特性，如解磷能力、吲哚乙酸（IAA）产生量、固氮酶活性以及甘露醇介导的渗透胁迫对铵排泄的影响，对野生型（A1501）和工程化的铵排泄型（1568/pVA3）固氮菌株进行了体外测试。在花盆和田间评估了A1501和1568/pVA3菌株对玉米植株的促生长效果，并采用N稀释技术评估植物氮中来自固氮的比例。结果表明，1568/pVA3菌株比A1501表现出更高的IAA产生量和固氮酶活性，并释放出大量铵。50天后，在所有测试条件下，接种1568/pVA3的玉米比接种A1501的玉米积累了更多的植物生物量（平均多3.3%）和固定氮（平均多39.4%）。在田间试验中，无论是否存在外源氮肥，用1568/pVA3接种种子分别使玉米产量提高了5.6%或5.9%。因此，在温室和田间测试的工程菌株在玉米生长参数和生物固氮方面表现优于野生型菌株。
