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Etude de déterminants moléculaires de Xanthomonas fuscans subsp. fuscans impliqués dans la colonisation de son hôte Phaseolus vulgaris

Abstract : The seed-borne pathogen Xanthomonas fuscans subsp. fuscans (Xff) is one of the causal agents of common bacterial blight of bean. From a contaminated seed, this pathogen colonizes aerial parts of its host during an entire growing season without engaging an infectious process; this ending finally in its transmission to the seeds. Objectives of this thesis were to identify molecular determinants of Xff and characterize their roles in three key stages of the bean asymptomatic colonization process. We identified two main types of candidate genes in Xff: in planta induced genes coding the type three secretion system (T3SS) and its effectors, genes involved in adhesion surface and biofilm formation processes.The germinating seed and seedling environments do not constitute restrictive environments for the bacterial multiplication. The absence of induced defense reactions at this stage implies that bacteria behave as saprophytes without molecular dialogue with the plant. In the bean phyllosphere, Xff survival depends partially on HrpG and HrpX regulators of the T3SS; active colonization and transmission to seeds by the vascular pathway require a functional T3SS. In non-host incompatible situation, X. campestris pv. campestris and its mutants in the T3SS can survive in the phyllosphere and transmit to the seeds with lower population sizes and frequencies than in the compatible situation. The six identified adhesins in Xff get involved during phyllosphere colonization or transmission to bean seeds by the vascular pathway. The transmission to the seeds by the floral pathway is a more general pathway and is only partially regulated by HrpG and HrpX.
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https://tel.archives-ouvertes.fr/tel-00348013
Contributor : Anne-Marie Plé <>
Submitted on : Wednesday, December 17, 2008 - 2:21:50 PM
Last modification on : Saturday, June 6, 2020 - 6:44:23 PM
Long-term archiving on: : Tuesday, June 8, 2010 - 5:35:23 PM

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  • HAL Id : tel-00348013, version 1
  • PRODINRA : 248676

Citation

Arnaud Darsonval. Etude de déterminants moléculaires de Xanthomonas fuscans subsp. fuscans impliqués dans la colonisation de son hôte Phaseolus vulgaris. Autre. Université d'Angers, 2008. Français. ⟨tel-00348013⟩

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