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Poster: Biology & Disease Mgmt: Bacteriology


The negative regulatory function of tepR for the virulence of Burkholderia glumae in rice is exerted via the quorum-sensing master regulator gene qsmR
J. HAM (1), J. Peng (1) (1) Louisiana State University Agricultural Center, U.S.A.

Burkholderia glumae causes bacterial panicle blight of rice, which is a globally emerging rice disease. The quorum-sensing system mediated by tofI and tofR plays a key role in the regulation of major virulence factors, such as toxoflavin (a phytotoxin), lipase and flagella. tepR, a newly found regulatory gene of B. glumae, negatively regulates multiple virulence factors including toxoflavin, lipase and exoprotease. In this study, a comparative RNA-seq analysis and a series of genetic research were performed to characterize the global regulatory function of tepR in B. glumae. The RNA-seq analysis revealed that none of the known regulatory genes required for toxoflavin production (tofI, tofM, tofR, toxJ, and toxR) was differentially expressed between the wild type (336gr-1) and its ΔtepR derivative (LSUPB401), while the structural genes for the toxoflavin biosynthesis and transport were more highly expressed in the ΔtepR background. Similar results were also obtained from quantitative reverse transcription PCR experiments, which validated the RNA-seq analysis. Likewise, expression of tepR was not affected by the tofI/tofR-mediated quorum sensing system. Interestingly, qsmR, a key regulatory factor for flagellum biogenesis, was found to be upregulated in the ΔtepR strain and essential for both toxoflavin production and exoprotease activity. These results suggest that tepR exerts its regulatory functions on toxoflavin and exoprotease through qsmR in this pathogen.