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Caractérisation des bactériophytochromes identifiés chez Rhodopseudomas palustris et Bradyrhizobium

Abstract : Rhodopseudomonas palustris is a photosynthetic purple bacteria which genome was completely sequenced. Six genes encoding putative bactériophytochromes are present in this genome. One of them plays an essential and unusual role in the synthesis of the photosystem. In this bacteria, three other bacteriophytochromes are localized near pucBA operons encoding polypeptides involved in the formation of light harvesting complexes associated with photosystem. First, this PhD work studied roles, properties and mechanisms of action of these three bacteriophytochromes. We showed that RpBphP2 and RpBphP3 act in tandem to regulate the expression of LH4 antennas. This signalling pathway use three reponse- regulators, one of them, Rpa3018 is rdox sensitive. In some strains of Rps. palustris, a bactériophytochrome, RpBphP4, lost its light sensitivity and acquired a redox sensibility while keeping its ability to regulate the expression of these antennas. In a second time, analysis of the genome sequence of two photosynthetic Bradyrhizobium (ORS278 and BTAi1) revealed, in each strain, the presence of a specific bacteriophytochrome probably acquired by horizontal transfer. The properties of these various bacteriophytochromes led highlighted the variety of this family of light sensors as well as the complexity of the signalling pathways which they introduce.
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Submitted on : Friday, February 22, 2008 - 3:16:27 PM
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Laurie Vuillet. Caractérisation des bactériophytochromes identifiés chez Rhodopseudomas palustris et Bradyrhizobium. Biochimie [q-bio.BM]. Université Montpellier II - Sciences et Techniques du Languedoc, 2007. Français. ⟨tel-00258550⟩

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