Laboratoire de Chimie Bactérienne UMR 7283

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9 novembre 2017: 1 événement


  • Séminaire LCB

    Jeudi 9 novembre 2017 14:00-15:00 - Antonia Herrero - Sevilla Universidad, Spain

    Séminaire LCB

    Résumé :

    "Transcriptional regulation of heterocyst formation in Anabaena"

    In cyanobacteria, the process of oxygenic photosynthesis greatly impacts most cellular features including metabolism, which is based on phototrophy and the assimilation of CO2 and inorganic nitrogen. The transcription factor NtcA is a global regulator of universal distribution in cyanobacteria that orchestrates N control and multiple other cellular responses to the C-to-N balance sensed by the 2-oxoglutarate cellular levels. NtcA-regulated processes include the differentiation of heterocysts, cells specialized in the fixation of atmospheric nitrogen, in filamentous multicellular cyanobacteria. During differentiation, NtcA promotes activation of HetR, another transcription factor which, together with NtcA, is required for the hierarchical and sequential activation of genes required for the extensive morphological and metabolic changes involved in the process. In Anabaena, heterocyst distribution follows a semiregular pattern along the filament that is initially established by the PatS morphogen. PatS is expressed in the cells that initiate differentiation, processed and exported to the neighboring cells to inhibit differentiation by blocking HetR activity. Regarding Ci assimilation, cyanobacteria has developed a C concentrating system that includes bicarbonate transporters, CO2-uptake systems and the carboxysome, a proteinaceous microcompartment that harbors ribulose bisphosphate carboxylase/oxygenase (Rubisco). The LysR-type regulator CmpR activates the expression of the cmp operon encoding an ABC-type HCO3 - transporter, and the gene cmpR is activated by NtcA, both in response to Ci limitation. Another LysR-type transcription factor, PacR, regulates the expression of ndh genes for CO2 uptake, rbc genes encoding RubisCo, and multiple elements involved in protection of the photosynthetic apparatus against oxidative damage, a principal problem faced by oxygenic phototrophs that is exacerbated under conditions of Ci limitation.

    Inv. : Christophe Bernard (Equipe Latifi - LCB)

    Lieu : Salle Georges Morin

    En savoir plus : Séminaire LCB