Diurnal switches in diazotrophic lifestyle increase nitrogen contribution to cereals

• Published in: Nature communications Vol. 14; no. 1; pp. 7516 - 16
• Main Authors: Tang, Yuqian, Qin, Debin, Tian, Zhexian, Chen, Wenxi, Ma, Yuanxi, Wang, Jilong, Yang, Jianguo, Yan, Dalai, Dixon, Ray, Wang, Yi-Ping
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 18.11.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 631/326/171/1818; 631/326/2522; 631/449/2676/2678; 631/61/338/552; 82/83; Amino acid substitution; Amino acids; Ammonia; Ammonium; Bacteria; Biosynthesis; Cereal crops; Cereals; Cultivation; Diurnal; E coli; Excretion; Gene regulation; Glutamate-ammonia ligase; Glutamine; Grain cultivation; High temperature; Humanities and Social Sciences; Klebsiella; multidisciplinary; Negative feedback; Nitrogen; Nitrogen fixation; Nitrogenase; Nitrogenation; Science; Science (multidisciplinary); Temperature; Temperature profiles
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-43370-4

Uncoupling of biological nitrogen fixation from ammonia assimilation is a prerequisite step for engineering ammonia excretion and improvement of plant-associative nitrogen fixation. In this study, we have identified an amino acid substitution in glutamine synthetase, which provides temperature sensitive biosynthesis of glutamine, the intracellular metabolic signal of the nitrogen status. As a consequence, negative feedback regulation of genes and enzymes subject to nitrogen regulation, including nitrogenase is thermally controlled, enabling ammonia excretion in engineered Escherichia coli and the plant-associated diazotroph Klebsiella oxytoca at 23 °C, but not at 30 °C. We demonstrate that this temperature profile can be exploited to provide diurnal oscillation of ammonia excretion when variant bacteria are used to inoculate cereal crops. We provide evidence that diurnal temperature variation improves nitrogen donation to the plant because the inoculant bacteria have the ability to recover and proliferate at higher temperatures during the daytime. Engineering ammonium excretion diazotrophs suffers from severe penalties to the bacteria. Here, the authors utilize a thermo-sensitive glutamine synthetase-based regulatory switch that permits diurnal changes in diazotrophic lifestyle, coincident with seasonal temperatures for cereal cultivation.