title: Drought tolerance conferred to sugarcane by association with Gluconacetobacter diazotrophicus: a transcriptomic view of hormone pathways.
abstract: Sugarcane interacts with particular types of beneficial nitrogen-fixing bacteria that provide fixed-nitrogen and plant growth hormones to host plants, promoting an increase in plant biomass. Other benefits, as enhanced tolerance to abiotic stresses have been reported to some diazotrophs. Here we aim to study the effects of the association between the diazotroph Gluconacetobacter diazotrophicus PAL5 and sugarcane cv. SP70-1143 during water depletion by characterizing differential transcriptome profiles of sugarcane. RNA-seq libraries were generated from roots and shoots of sugarcane plants free of endophytes that were inoculated with G. diazotrophicus and subjected to water depletion for 3 days. A sugarcane reference transcriptome was constructed and used for the identification of differentially expressed transcripts. The differential profile of non-inoculated SP70-1143 suggests that it responds to water deficit stress by the activation of drought-responsive markers and hormone pathways, as ABA and Ethylene. qRT-PCR revealed that root samples had higher levels of G. diazotrophicus 3 days after water deficit, compared to roots of inoculated plants watered normally. With prolonged drought only inoculated plants survived, indicating that SP70-1143 plants colonized with G. diazotrophicus become more tolerant to drought stress than non-inoculated plants. Strengthening this hypothesis, several gene expression responses to drought were inactivated or regulated in an opposite manner, especially in roots, when plants were colonized by the bacteria. The data suggests that colonized roots would not be suffering from stress in the same way as non-inoculated plants. On the other hand, shoots specifically activate ABA-dependent signaling genes, which could act as key elements in the drought resistance conferred by G. diazotrophicus to SP70-1143. This work reports for the first time the involvement of G. diazotrophicus in the promotion of drought-tolerance to sugarcane cv. SP70-1143, and it describes the initial molecular events that may trigger the increased drought tolerance in the host plant.
authors.affiliation: Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, RJ, Brazil.
authors.forename: Lívia
authors.initials: L
authors.lastname: Vargas
authors.affiliation: Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, RJ, Brazil.
authors.forename: Ailton B
authors.initials: AB
authors.lastname: Santa Brígida
authors.affiliation: Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, RJ, Brazil.
authors.forename: José P
authors.initials: JP
authors.lastname: Mota Filho
authors.affiliation: Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, RJ, Brazil.
authors.forename: Thais G
authors.initials: TG
authors.lastname: de Carvalho
authors.affiliation: Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, RJ, Brazil; Universidade Federal da Integração Latino-Americana, Foz do Iguaçu, PR, Brazil.
authors.forename: Cristian A
authors.initials: CA
authors.lastname: Rojas
authors.affiliation: Department of Plant Systems Biology, VIB, Gent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, Gent, Belgium.
authors.forename: Dries
authors.initials: D
authors.lastname: Vaneechoutte
authors.affiliation: Department of Plant Systems Biology, VIB, Gent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, Gent, Belgium.
authors.forename: Michiel
authors.initials: M
authors.lastname: Van Bel
authors.affiliation: Fasteris SA, Plan-les-Ouates, Switzerland.
authors.forename: Laurent
authors.initials: L
authors.lastname: Farrinelli
authors.affiliation: Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, RJ, Brazil.
authors.forename: Paulo C G
authors.initials: PC
authors.lastname: Ferreira
authors.affiliation: Department of Plant Systems Biology, VIB, Gent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, Gent, Belgium.
authors.forename: Klaas
authors.initials: K
authors.lastname: Vandepoele
authors.affiliation: Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, RJ, Brazil.
authors.forename: Adriana S
authors.initials: AS
authors.lastname: Hemerly
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000222:Adaptation, Physiological / Q000187:drug effects / Q000235:genetics*; D015415:Biomarkers / Q000378:metabolism*; D055864:Droughts; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D041821:Gluconacetobacter / Q000502:physiology*; D009586:Nitrogen Fixation; D020411:Oligonucleotide Array Sequence Analysis; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D031786:Saccharum / Q000254:growth & development* / Q000382:microbiology; D015398:Signal Transduction; D013559:Symbiosis / Q000502:physiology*
chemical_list: D015415:Biomarkers; D010937:Plant Growth Regulators; D010940:Plant Proteins; D012333:RNA, Messenger; D000040:Abscisic Acid