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XopJ6, a new member of the XopJ family of type III effectors, in Xanthomonas perforans.

Fernanda Iruegas-Bocardo: Department of Plant Pathology, University of Florida

<div>Bacterial leaf spot on pepper and tomato is caused by four <em>Xanthomonas</em> species. Of these, <em>X. perforans </em>(<em>Xp</em>) is typically a specific pathogen of tomato. The type III secretion effector AvrBsT (XopJ2) belongs to the XopJ effector family. It induces a hypersensitive response (HR) in pepper, but behaves as a virulence gene in tomato, compromising its defense responses. We describe a new member of the XopJ effector family, XopJ6. An homology analysis using HMMER showed that this gene belongs to the serine/threonine acetyltransferase XopJ effector family, and contains its signature catalytic core (His, Glu and Cys), required to induce HR in resistant plants. A tBLASTn analysis revealed its presence in 14 out of 137 sequenced strains collected from Florida, China, Thailand and Nigeria, all belonging to a unique phylogenetic lineage. XopJ6 is closely related to AvrBsT, sharing 71.5% sequence identity, but a genomic context analysis revealed that it is located at different locus. We demonstrated that XopJ6 induces an hypersensitive response in pepper after cloning the gene into pepper pathogenic <em>X. euvesicatoria </em>strain 85-10. Our results provide further evidence that the XopJ family of effectors are important virulence and host-range delimiting factors in <em>Xp</em>.</div>