Résumé
The Xanthomonas genus includes several plant pathogens responsible for significant croplosses worldwide. Most of the functional studies of virulence in this genus have been carriedout by directed mutagenesis through homologous recombination. However, this strategy is576cumbersome for the study of gene families. CRISPR interference (CRISPRi) allows precisesilencing of target genes by using a catalytically dead Cas9 (dCas9) which interferes withgene expression. Because of its RNA-directed nature, this technology can be used forsilencing several genes in a single experiment in bacteria and other organisms. Weimplemented a CRISPRi strategy to silence several members of the Transcriptional activator-like effectors (TALE) gene family at once in four different species of Xanthomonas. Ourresults underscore the importance of the activation of the SWEET gene family in cassavaupon infection by Xanthomonas phaseoli pv. manihotis. Remarkably, we report theimportance of this gene family in the infection of this host by the non-vascular pathogen X.cassavae. In addition, we successfully silenced several TALE genes in a total of five species,including X. oryzae pv. oryzae, X. citri pv. citri and X. campestris pv. campestris usingCRISPRi, confirming the importance of this gene family in these pathosystems. The CRISPRitool can be further modulated to silence sets of genes within a gene family for functionalstudies in Xanthomonas and other plant pathogenic bacteria.