Xanthomonas campestris pv. campestris (Xcc) is the causal agent of black rot disease, which is the most important and destructive bacterial disease of Brassica crops. Most Xanthomonas species translocate Transcription Activator-Like Effectors (TALEs) proteins inside plant cells using their type III secretion machinery. TALEs are a unique type of bacterial effector proteins that help the pathogen to exploit and modify the plant environment by directly altering the expression of plant genes to the benefit of the bacteria. TALEs play an essential role in many plant diseases caused by Xanthomonas spp. but the contribution of TALEs to virulence of Xcc has not been characterized. We identified a rich repertoire of tal genes (TALome) in Xcc and studied its functional role in disease development. First, we successfully silenced the tal genes in two Xcc strains using CRISPRi technology, demonstrating the role of TALEs for Xcc pathogenicity. In addition, the contribution of individual Xcc TALEs to bacteria virulence was tested by gain and loss-of-function experiments. Our data provide a platform to explore the roles of TALEs in black rot disease. We will present our latest results on the mechanisms of TALE-mediated susceptibility in Brassicaceae