Genetic Controls of Biomass Increase in Sugarcane by Association with Beneficial Nitrogen-Fixing Bacteria

Carvalho, TLG¹; Ballesteros, HGF¹;  Mota Filho,  JP¹; Hardoim, P¹.; Fernandes T.M.D¹; Mendes, J.L.M. ¹; Atella, M. ¹; Baldani, JI²; Ferreira PCG¹, Hemerly, AS¹. hemerly@bioqmed.ufrj.br

¹ Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, 21.941-590, Rio de Janeiro, RJ, Brazil; ²Embrapa Agrobiologia, BR465, Km47, 23851-970, Seropédica, RJ, Brazil.

Sugarcane is the most important bioenergy grass in Brazil, being successfully used for first generation ethanol production from sugar. More recently, energy cane genotypes are being created in Brazil as an alternative for second generation ethanol production from lignocellulosic biomass. The success of the biofuel programs led to an increase in the demand of this crop productivity in the country for the next years. An important biotechnological challenge of this century is to develop tools to apply for a sustainable agriculture that would increase productivity using less fertilizers, pesticides, water and cultivated area. The associations that occur between sugarcane and other grasses with nitrogen-fixing associative and endophytic bacteria have raised a large interest in their use in agriculture, in view of the positive effects on biomass, productivity and tolerance against stresses. The promotion of plant growth by the endophytic nitrogen-fixing bacteria might be mediated by providing nitrogen trough Biological Nitrogen Fixation (BNF) and hormones. Inoculants of associative and endohytic diazotrophic bacteria had been shown to lead to positive results on sugarcane yields, which are dependent on the plant genotype and soil conditions. Our group has been studying plant genes involved in the establishment of a beneficial type of association with nitrogen-fixing bacteria, aiming to assist in the development of more responsive cultivars to inoculants of beneficial diazotrophs. An integrated differential transcriptome was generated by Illumina RNA sequencing and it provided an overview of sugarcane metabolism, growth and development controlled by nitrogen, water and endophytic nitrogen-fixing bacteria during a successful association. All together, the data suggest that an important control of the efficiency of the association is already set in the early stages of plant-bacterium recognition, when specific plant genotypes sense the environment and regulate several plant signaling pathways involved in microorganism recognition and plant defense.

This work was supported by INCT, CNPq, FAPERJ & CAPES.