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Evolution des génomes microsporidiens et mécanisme d'adaptation moléculaire chez les parasites intracellulaires obligatoires

Abstract : Microsporidia are obligate intracellular parasites characterized by a unique invasive mechanism, and, in some species, by a highly compact nuclear genome. To improve our knowledge of gene expression in these opportunistic pathogens, experiments on transcriptional regulation mechanisms were undertaken. In the microsporidia Encephalitozoon cuniculi (a mammalian parasite with a genome size of 2.9 Mb), we demonstrated a polycistronic gene organization. At the time of transcription, the transcripts are randomly processed leading to an mRNA population composed of monocistronic and polycistronic mRNA. To study the structure of microsporidian genomes and their adaptation capacities, the sequencing of Brachiola algerae genome (an insect and mammalian microsporidia) has been initiated in collaboration with Genoscope. Thirty chromosome bands from 160 to 2240 kb were identified, giving a haploid genome size estimated of 23 Mb. The study of the chromosomal distribution of the 16S rRNA unit showed the presence of 16S copy on at least 9 chromosome bands. The first analysis of this AT rich genome (more than 75%) revealed the presence of different kinds of transposable elements as well as genes encoding for enzymes involved in the RNA interference process. We further demonstrated that two Anopheles gambiae cellular lineages Sua4.0 (haemocytic cell) and Mos 55 (embryonic cells) can be infected by B. algerae providing a model to study in vitro the interaction between An. gambiae and its pathogens. The successful use of the RNA interference in these two types of cells will contribute to a better understanding of the adaptation mechanisms of pathogens like P. falciparum and B. algerae.
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Submitted on : Monday, July 16, 2012 - 2:31:21 PM
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  • HAL Id : tel-00718201, version 1

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Abdel Belkorchia. Evolution des génomes microsporidiens et mécanisme d'adaptation moléculaire chez les parasites intracellulaires obligatoires. Biochimie, Biologie Moléculaire. Université Blaise Pascal - Clermont-Ferrand II; Université d'Auvergne - Clermont-Ferrand I, 2007. Français. ⟨NNT : 2007CLF21766⟩. ⟨tel-00718201⟩

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