Genomic acquisitions in emerging populations ofXanthomonas vasicolapv.vasculoruminfecting corn in the U.S. and Argentina

Abstract

AbstractXanthomonas vasicolapv.vasculorum (Xvv)is an emerging bacterial plant pathogen that causes bacterial leaf streak on corn. First described in South Africa in 1949, reports of this bacteria have greatly increased in the past years in South America and in the U.S., where it is now present in most of the corn producing states. Phenotypic characterization showed that the emerging U.S. and South American Xvvpopulations may have increased virulence in corn compared to older strains. To understand the genetic mechanisms behind the increased virulence in this group, we used comparative genomics to identify gene acquisitions inXvvgenomes from the U.S. and Argentina. We sequenced 41 genomes ofXvvand the related sorghum-infectingX. vasicolapv.holcicola(Xvh).A comparison of all availableX. vasicolagenomes showed the phylogenetic relationships in the group and identified clusters of genes associated with the emergingXvvpopulations. The newly acquired gene clusters showed evidence of horizontal transfer toXvvand included candidate virulence factors. One cluster, in particular, corresponded to a prophage transferred fromXvhto allXvvfrom Argentina and the U.S. The prophage contains putative secreted proteins, which represent candidates for virulence determinants in these populations and await further molecular characterization.