Wongdee Jenjira, Piromyou Pongdet, Songwattana Pongpan, Greetatorn Teerana, Teaumroong Neung, Boonkerd Nantakorn, Giraud Eric, Nouwen Nico, Tittabutr Panlada
Institute of Research and Development, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
Front Microbiol. 2023 Feb 16;14:1131860. doi: 10.3389/fmicb.2023.1131860. eCollection 2023.
RpoN is an alternative sigma factor (sigma 54) that recruits the core RNA polymerase to promoters of genes. In bacteria, RpoN has diverse physiological functions. In rhizobia, RpoN plays a key role in the transcription of nitrogen fixation () genes. The sp. DOA9 strain contains a chromosomal (c) and plasmid (p) encoded RpoN protein. We used single and double mutants and reporter strains to investigate the role of the two RpoN proteins under free-living and symbiotic conditions. We observed that the inactivation of or severely impacts the physiology of the bacteria under free-living conditions, such as the bacterial motility, carbon and nitrogen utilization profiles, exopolysaccharide (EPS) production, and biofilm formation. However, free-living nitrogen fixation appears to be under the primary control of RpoNc. Interestingly, drastic effects of and mutations were also observed during symbiosis with . Indeed, inoculation with , , and double mutant strains resulted in decreases of 39, 64, and 82% in the number of nodules, respectively, as well as a reduction in nitrogen fixation efficiency and a loss of the bacterium's ability to survive intracellularly. Taken together, the results show that the chromosomal and plasmid encoded RpoN proteins in the DOA9 strain both play a pleiotropic role during free-living and symbiotic states.
RpoN是一种替代的σ因子（σ54），它将核心RNA聚合酶招募到基因的启动子上。在细菌中，RpoN具有多种生理功能。在根瘤菌中，RpoN在固氮基因的转录中起关键作用。sp. DOA9菌株含有染色体（c）和质粒（p）编码的RpoN蛋白。我们使用单突变体和双突变体以及报告菌株来研究这两种RpoN蛋白在自由生活和共生条件下的作用。我们观察到，在自由生活条件下，c或p的失活会严重影响细菌的生理功能，如细菌运动性、碳和氮利用谱、胞外多糖（EPS）产生和生物膜形成。然而，自由生活固氮似乎主要受RpoNc的控制。有趣的是，在与共生期间也观察到c和p突变的显著影响。事实上，接种c、p和双突变菌株分别导致根瘤数量减少39%、64%和82%，以及固氮效率降低和细菌在细胞内生存能力丧失。综上所述，结果表明DOA9菌株中染色体和质粒编码的RpoN蛋白在自由生活和共生状态下均发挥多效性作用。
