Transcriptome and proteome profiles of the diazotroph Nitrospirillum amazonense strain CBAmC in response to the sugarcane apoplast fluid

Background and aims The endophytic diazotrophic strain CBAmC of Nitrospirillum amazonense has been reported as a plant growth promoter of sugarcane variety RB867515 when grown under field conditions. The present work aimed to assess the influence of apoplast fluid from RB867515 on the transcriptomic and proteomic profiles of CBAmC cultured in vitro . Methods RNA-Seq in Ion Proton™ and ESI-LC-MS/MS peptide analysis were used to evaluate the transcriptomic and proteomic profiles, respectively, of CBAmC exposed for 2 h to the sugarcane apoplast fluid. Results The bacterial transcriptomic and proteomic profiles were well correlated. The overall response of CBAmC to the apoplast fluid included overexpression of defense systems against reactive oxygen species (ROS) and osmotic stress, RND efflux pumps for toxic compounds, Sec and Tat secretory systems, and assimilative metabolism of iron. In contrast, active transporters of organic compounds, chemotaxis system and flagellum structure were underexpressed. Conclusions The bacterial metabolic pathways / functions activated in response to the sugarcane apoplast fluid are most likely related to its adaptation to the peculiar characteristics of the fluid. The activation of some of those functions could be determinant for its adaptation to the sugarcane apoplastic niche, and perhaps be involved in the previously observed effect of promoting plant growth.