Diversity of the rice pathogenic bacterium Burkholderia glumae in virulence, regulatory system, and genome structure associated with genomic islands
Jong Hyun Ham: Louisiana State University
<div><em>Burkholderia glumae </em>is a gram-negative plant pathogenic bacterium causing bacterial panicle blight in rice. The phytotoxin toxoflavin, along with its derivatives, is a major virulence factor of this pathogen, and the quorum-sensing mediated by the <em>luxI/luxR </em>homologs <em>tofI/tofR </em>plays a pivotal role in the regulation of bacterial pathogenesis. Genetic studies of two virulent strains 336gr-1 and 411gr-6 showing contrasting phenotypes in pigmentation revealed that the regulatory system for bacterial pathogenesis is different between these two strains. Remarkably, 411gr-6 retained pathogenic functions in the absence of the <em>tofI/tofR </em>quorum-sensing system, while 336gr-1 completely lost its pathogenic function in the same genetic background. We recently completed whole genome sequencing of these two virulent strains and a naturally avirulent strain 957856-41-c to investigate the genomic structure determining the phenotypic variations of these strains. Comparative analysis of these three genome sequences and two reference genome sequences in the NCBI database (one for the virulent strain BGR1 and the other for the avirulent strain ATCC33617) revealed significant variations in the genome structure across the five strains of <em>B. glumae</em>. These variations were mainly associated with the presence of multiple strain-specific genomic islands (GIs). The features of the strain-specific GIs associated with the phenotypic variations of <em>B. glumae </em>strains will be discussed.</div>
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