Fermentation characteristics of Agrobacterium sp. with oxygen regulation gene fnrN mutation and genes expression analysis based on RNA-Seq

Abstract:

[Objective] To study the effect of Crp family transcriptional regulator gene fnrN mutation on the fermentation characteristics and genes expression in Agrobacterium sp. ATCC 31749. [Methods] A suicide plasmid pJQ-fnrN-kan was constructed and transformed into wild type strain by triparental conjugation method to obtain the fnrN mutation strain (ΔfnrN). The cell growth and fermentation characteristics of ΔfnrN were compared with that of the wild strain, then comparative transcriptomes with RNA-Seq were used to analyze the expression changes of genes in curdlan-producing phase due to fnrN mutation. [Results] The level of curdlan production was reduced by 22.0% because of fnrN mutation. Transcriptomes analysis revealed that 186 genes expressed significantly different (|log2(|fold change|)|≥1 and q≤0.001), and about 65% differently expressed genes were up-regulated. The key genes (crdASC) in curdlan synthesis were repressed in different degree, the fnrN mutation significantly down-regulated the expression of ecfR and sinR, coding ECF family RNA polymerase sigma factor and Fnr family regulator of biofilm formation respectively. The transcription levels of genes (cydAB, cy2 and fixNOPQ) related with cytochrome were down-regulated 2?13 times. [Conclusion] The fnrN regulates curdlan synthesis by controlling the expression of ecfR and sinR, and takes part in oxygen signal regulation through down-regulating the expression of fixNOPQ, which is helpful to enrich the understanding of oxygen regulation system in Agrobacterium sp.