Plant Signaling during Sugarcane Colonization with Endophytic Nitrogen-Fixing Bacteria

Associations that occur between sugarcane and other grasses with nitrogen-fixing endophytic bacteria have raised a large interest in their use in agriculture, in view of the positive effects on root development, and the increase in biomass and productivity. Endophytic nitrogen-fixing bacteria might promote plant growth by providing hormones and nitrogen trough Biological Nitrogen Fixation (BNF). It has been demonstrated that BNF efficiency is dependent on plant genotype and on specific soil conditions where association is established, such as nitrogen fertility and water content. Our group has been studying plant signaling mechanisms involved in the establishment of this particular type of association with nitrogen-fixing bacteria, aiming to investigate the role of plant genotype and soil conditions in the efficiency of the association. Next generation sequencing technologies are being applied to compare expression profile in two sugarcane BNF contrasting genotypes and in response to soil conditions, such as nitrogen sources and water deficit. An integrated differential transcriptome was generated and it provided an overview of sugarcane metabolism, growth and development controlled by nitrogen, water and endophytic nitrogen-fixing bacteria during a successful association. We propose that several levels of regulation might be operating in sugarcane during the association with endophytic diazotrophic bacteria. To establish a beneficial association, several pathways controlling plant growth and development might be integrated with the plant response to the endophytic bacteria. Finally, the various sugarcane regulatory mechanisms might be coordinated and connected to plant genotype and environmental signals, in order to control the success of the association.