A novel essential small RNA, sSp_p6 influences nitrogen fixation in Azospirillum brasilense

Azospirillum brasilense Sp245, a diazotrophic plant growth-promoting bacterium influences host plants via wellknown mechanisms, gene interactions and confers abiotic and biotic stress tolerance mediated by signalling molecules. We present here, the functional characterization of a small RNA (sRNA), sSp_p6, identified from the 468 sRNAs identified in A. brasilense Sp245 and confirmed its involvement in nitrogen metabolism in the strain. sSp_p6 expression was found to be modulated in carbon and nitrogen stress while forming an interactive network with the target genes, vnfG (encoding vanadium-dinitrogenase) and σ-54 (sigma factor, interaction region) thereby establishing an essential role of this sRNA in biological nitrogen fixation by the strain. Additionally, upon inoculation with sSp_p6 overexpressing mutant, the host plant Sorghum exhibited increased lateral root formation, which led to improved plant root morphology.