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Physiological characterization and gene expression profile of the transport of nitrogen in contrasting cultivars for biological nitrogen fixation of sugarcane (Saccharum spp.)

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Layanne Batista Souza
Total Authors: 1
Document type: Doctoral Thesis
Press: Piracicaba.
Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz
Defense date:
Examining board members:
Antonio Vargas de Oliveira Figueira; Welington Luiz de Araujo; João Lucio de Azevedo; Vera Lúcia Divan Baldani; Joni Esrom Lima
Advisor: Antonio Vargas de Oliveira Figueira

Sugarcane has a large economic importance to Brazil, and it\'s the expansion of cultivation to marginal soils requires a larger application of nitrogen fertilizers (N) to maintain yield. In most producing countries, N fertilization is based on high application rates, whereas in Brazil N fertilization is relatively low, possibly due in part, to the process of biological nitrogen fixation (BNF). In addition, plants acquire inorganic N sources from the soil by membrane transporters that may be regulated by association with microorganisms. This study aimed to characterize the ammonium and nitrate transport evaluating the gene expression profile of the major transporters grown in vitro in association with diazotrophic bacteria. It was also described the bacterial community in micropropagated plants, as well as the effect of N fertilization or inoculation with nitrogen fixing bacteria in mature plants. \'SP70-1143\' and \'Chunee\' which contrasted to BNF, were used in in vitro experiments in several concentrations and N source, in association or not with a strain of Gluconacetobacter diazotrophicus or a bacteria mixture (G. diazotrophicus, Herbaspirillum seropedicae, H. rubrisubalbicans, Azospirillum amazonense and Burkholderia tropica). The characterization of the N transport by uptake assays with 15N-labeled ammonium and nitrate, revealed that the interaction between sugarcane x G. diazotrophicus induced, the nitrate transporter gene ScNRT2.1 expression, which lead to trend to increase nitrate influx, as well as the ammonium transporter genes ScAMT1.1 and ScAMT1.3, resulting in higher ammonium influx in \'SP70-1143\'. Sugarcane associated with the bacterial mixture revealed a transcriptional induction of ScAMT1.1 resulting in larger ammonium acquisition in \'SP70-1143\'. Further, the presence of bacteria in vitro for 30 days, although transient, possibly favored the expression of nitrate transporters ScNRT1.1 and ScNRT2.1, and the ammonium transporter ScAMT1.1, resulting in accumulation of 15N-ammonium nitrate in \'SP70-1143\'. A bacterial community associated with in vitro plants of \'SP70-1143\' and \'Chunee\' was detected with different composition between genotypes, and which changed with artificial inoculation. For plants grown in the field, the bacterial community was affected by N fertilization but not by inoculation with diazotrophic. These results indicate that the inoculation with diazotrophic bacteria appears to induce the expression of the major ammonium and nitrate transporters genes in \'SP70-1143\' plants resulting in higher uptake of inorganic N sources. (AU)

FAPESP's process: 11/22890-2 - Physiological characterization and gene expression profile of the transport of nitrogen in contrasting cultivars of sugarcane (Saccharum spp) for the process of biological nitrogen fixation
Grantee:Layanne Batista Souza
Support type: Scholarships in Brazil - Doctorate