Résumé
Transcription Activator Like effectors (TALs) are important factors for the pathogenicity of Xanthomonas. They are responsible for disease in susceptible plants by activating specific susceptibility genes, but they fortuitously trigger defense responses in plants where this function has been hijacked to activate resistance genes. If their mechanisms of delivery and modes of action into the host cell are now largely deciphered, little is known about the way they appeared in Xanthomonas and how they evolved to instigate such varied symptomatologies. We analyzed the diversity of TAL genes in a large collection of Xanthomonas citri pv. citri (XCI) corresponding to broad host range strain s and narrow host range strain s in order to investigate mechanisms of TAL evolution, especially in relation with their impact on host range definition. Comparison of the potential Citrus target genes for the different TALs existing in Xci is included in the analysis in order to hypothesize the effect of host variation on TAL evolution. (Texte intégral)