Endophytic nitrogen-fixing bacteria have been isolated from graminaceous plants such as maize, rice, and sugarcane. They are thought to promote plant growth, not only by fixing nitrogen, but also by the production of plant hormones. The molecular mechanisms involved in this interaction are not yet clear. In this work, the identification of a receptor-like kinase (RLK), named SHR5, which may participate in signal transduction involved in the establishment of plant-endophytic bacteria interaction is described for the first time. SHR5 seems to be part of a novel subclass of RLKs present in a wide range of plant species. The expression of this gene is down-regulated in sugarcane plants associated exclusively with beneficial endophytic bacteria and is not a general response caused by micro-organisms or abiotic stress. In addition, more successful sugarcane-endophytic bacteria associations have a more pronounced decrease in SHR5 expression, suggesting that SHR5 mRNA levels in plant cells are inversely related to the efficiency of the association.
Nitrogen-fixing bacteria have been isolated from sugarcane in an endophytic and beneficial interaction that promotes plant growth. In this work, for the first time, the involvement of ethylene signalling in this interaction was investigated by molecular characterizing members of this pathway in sugarcane. The expression pattern of a putative ethylene receptor (SCER1) and two putative ERF transcription factors (SCERF1 and SCERF2) show exclusive modulation in plants inoculated with the diazotrophic endophytes. The gene expression profile of SCER1, SCERF1, and SCERF2 is differentially regulated in sugarcane genotypes that can establish efficient or inefficient associations with diazotrophic micro-organisms, exhibiting high or low biological nitrogen fixation (BNF) rates, respectively. In addition, SCER1, SCERF1, and SCERF2 expression is different in response to interactions with pathogenic and beneficial micro-organisms. Taken together, that data suggest that SCER1, SCERF1, and SCERF2 might participate in specific ethylene signalling cascade(s) that can identify a beneficial endophytic association, modulating sugarcane responses toward the diazotrophic endophytes.
Several Brazilian sugarcane varieties have the ability to grow with little addition of inorganic nitrogen fertilizers, showing high contributions of Biological Nitrogen Fixation (BNF). A particular type of nitrogen-fixing association has been described in this crop, where endophytic diazotrophs such as Gluconacetobacter diazotrophicus and Herbaspirillum spp. colonize plant tissues without causing disease symptoms. In order to gain insight into the role played by the sugarcane in the interaction between this plant and endophytic diazotrophs, we investigated gene expression profiles of sugarcane plants colonized by G. diazotrophicus and H. rubrisubalbicans by searching the sugarcane expressed sequence tag SUCEST Database (http://sucest.lad.ic.unicamp.br/en/). We produced an inventory of sugarcane genes, candidates for exclusive or preferential expression during the nitrogen-fixing association. This data suggests that the host plant might be actively involved in the establishment of the interaction with G. diazotrophicus and H. rubrisubalbicans.
RESUMO Este artigo apresenta parte do desenvolvimento da pesquisa de Tese intitulada Traduções de um Lugar: Os Serviços destinados à Alimentação Fora do Lar, em andamento no Programa de Pós-Graduação em Arquitetura-PROARQ/FAU-UFRJ, e explora a possibilidade de ampliação do leque de ações a serem desenvolvidas para o embasamento prático-teórico do projeto visando a qualidade dos ambientes destinados à alimentação fora do lar. O estudo toma como base a assertiva de que a sensação de pertencimento no mundo globalizado não se dá mais somente na esfera do mundo vivido, regionalizado, onde o indivíduo cultiva a sua história e a dos seus, mas também se relativiza através de uma rede onde os meios de comunicação funcionam como instrumento para a sua confecção. O escopo metodológico para a pesquisa propõe associar as diretrizes da Teoria Ator-Rede (TAR) aos processos de Avaliação Pós-Ocupação (APO), o que permitirá uma abordagem muito mais rica pela multiplicidade de elementos envolvidos na análise. Como resultado, procura evidenciar a necessidade de incorporação de métodos investigativos de campo ao processo de projeto e fomentar a ampliação de uma base de dados que beneficie e contribua para o aperfeiçoamento dos projetos de arquitetura destinados ao setor. A importância e a originalidade deste trabalho se concentram na análise das narrativas produzidas pelos diversos atores-humanos e não-humanos-participantes das relações desenvolvidas nestes lugares. Estas relações não estão restritas somente ao ato de alimentar-se, mas se desenrolam em um palco repleto de significantes expressivos da ação em rede do espaço/tempo vivido na atualidade. PALAVRAS-CHAVE Avaliação de desempenho do ambiente construído, Teoria Ator-Rede, projeto do lugar, serviços de alimentação.
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