XopC and XopJ, Two Novel Type III Effector Proteinsfrom Xanthomonas campestris pv.vesicatoria

ABSTRACT Pathogenicity of the gram-negative plant pathogen Xanthomonas campestris pv. vesicatoria depends on a type III secretion (TTS) system which translocates bacterial effector proteins into the plant cell. Previous transcriptome analysis identified a genome-wide regulon of putative virulence genes that are coexpressed with the TTS system. In this study, we characterized two of these genes, xopC and xopJ. Both genes encode Xanthomonas outer proteins (Xops) that were shown to be secreted by the TTS system. In addition, type III-dependent translocation of both proteins into the plant cell was demonstrated using the AvrBs3 effector domain as a reporter. XopJ belongs to the AvrRxv/YopJ family of effector proteins from plant and animal pathogenic bacteria. By contrast, XopC does not share significant homology to proteins in the database. Sequence analysis revealed that the xopC locus contains several features that are reminiscent of pathogenicity islands. Interestingly, the xopC region is flanked by 62-bp inverted repeats that are also associated with members of the Xanthomonas avrBs3 effector family. Besides xopC, a second gene of the locus, designated hpaJ, was shown to be coexpressed with the TTS system. hpaJ encodes a protein with similarity to transglycosylases and to the Pseudomonas syringae pv. maculicola protein HopPmaG. HpaJ secretion and translocation by the X. campestris pv. vesicatoria TTS system was not detectable, which is consistent with its predicted Sec signal and a putative function as transglycosylase in the bacterial periplasm.

Xanthomonas resistance in Hungarian 4 spice pepper varieties

With a view to further enhance the reputation of Hungarian spice pepper it was necessary to improve resistance to the bacterium Xanthomonas campestris pv.vesicatoria, the most dangerous pathogen of pepper varieties. From among the familiar resistance genes in Hungary only the gene Bs-2 could provide sufficient protection against the aggressiveness spectrum of the bacterium species X.c.pv. vesicatoria. The first results of the resistance breeding are the spice pepper varieties Kaldom and Kalorez. In addition to the Bs-2 gene attempts are also being made at building in a gds gene into pepper, a gene creating a general defense system, a different strategy towards Xanthomonas campestris pv. vesicatoria.