Characterization of Mo- and Fe-Nitrogenases expression in the Plant Growth-Promoting Endophyte Kosakonia radicincitans UYSO10

Background and aims Nitrogenases enzymes are responsible for the biological fixation of nitrogen. While organisms capable of fixing nitrogen commonly possess the Mo-nitrogenase, some also have the V- and/or the Fe-nitrogenase. The strain Kosakonia radicincitans UYSO10 encodes two functional enzymes: Mo-nitrogenase and Fe-nitrogenase, both contribute to the growth promotion observed in sugarcane-inoculated plants. However, the regulatory mechanisms that determine their expression remain unclear. This study aimed to characterize the specific expression patterns associated with each nitrogenase.Methodology To achieve this, two complementary approaches were employed. First, Mo- and Fe-nitrogenases reporter vectors were constructed and evaluated under different in vitro and in vivo conditions during interactions with sugarcane plants. Additionally, transcriptomic and proteomic analyses were performed to identify transcripts and peptides associated with structural proteins of nitrogenases in co-culture with sugarcane plants.Results Overall, the Mo-nitrogenase was preferentially expressed, while the Fe-nitrogenase expression was detected under conditions that mimic the internal environment of the stem tissues.Conclusions These results suggest the potential role of the Fe-nitrogenase during the endophytic plant interaction. These findings further validate K. radicincitans UYSO10 as an excellent model for investigating plant-endophytic interactions, particularly in elucidating the functional roles associated with both nitrogenases.