Recently, the latest research of the microbial functional genomics team led by Professor Min Lin (Biotechnology Research Institute, Chinese Academy of Agricultural Sciences) demonstrated for the first time the biological function of NfiS involved in oxidative stress adaptation. It lays an important theoretical foundation for revealing the stress adaptation mechanism of nitrogen-fixing bacteria and the oxygen protection mechanism of nitrogenase. It also provided a new idea for enhancing the nitrogen-fixing efficiency of root-associated azotobacter under abiotic stress and realizing fertilizer-saving, yield-increasing and efficiency-increasing. The related result was online published in the latest issue of the 《Journal of Bacteriology》.
Nitrogen-fixing Pseudomonas stutzeri A1501 was isolated from the rice rhizosphere, the nitrogenase activity of which is highly affected by the abiotic stress factors in the rhizophere, especially the oxidative stress factor. Thus, nitrogen-fixing bacteria have to evolve various strategies to meet the energy demands of nitrogen fixation while protecting nitrogenase from oxygen damage. Currently, the research on the oxygen protection mechanism of biological nitrogen fixation is a hot issue in the field of nitrogen fixation, but there is no direct scientific evidence on whether non-coding RNA is involved in the oxygen protection of nitrogenase.
Our previous studies indicated that A1501 possesses a novel non-coding RNA NfiS that is involved in the regulation of optimal nitrogenase activity. The synthesis of NfiS was induced under oxidative stress, and the oxidative stress resistance of an nfiS mutant strain was decreased significantly, indicating that NifS might be involved in the oxidative stress response. However, its target genes and mechanism under oxidative stress have yet to be defined. In this work, we found that katB expression is dependent on OxyR, and that both OxyR and KatB are essential for optimal oxidative stress resistance and nitrogenase activites. Microscale thermophoresis assays indicated direct base pairing between katB mRNA and NfiS at both sites 1 and 2, thus enhancing the half-life of the transcript. The working model for NfiS in P. stutzeri tentatively illustrates the coordinative regulatory roles of NfiS in integrating adaptation to oxidative stress and nitrogen fixation. At the posttranscriptional level, NfiS directly pairs with the mRNAs of both the catalase gene katB and the nitrogenase gene nifK, thus linking total catalase activity and optimal nitrogen fixation; on the other hand, under O2-insufficient conditions, H2O2 at low concentrations is detoxified by H2O2-inducible catalases, leaving O2 as a by-product to support nitrogen fixation.
非编码RNA NfiS介导的氧化胁迫应答和最佳固氮酶活性的协同调控模型
Model for the NfiS-mediated regulatory network and oxidative stress response in P. stutzeri A1501
This work was supported by the National Basic Research Program of China and National Science Foundation of China. Master student Hongyang Zhang and Dr. Yuhua Zhan are the co-first authors of the paper. Professor Min Lin is the corresponding author.
Original link: https://jb.asm.org/content/jb/201/19/e00334-19.full.pdf
|