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An RNA-sequencing analysis implicates the presence of multiple cell-to-cell signaling pathways in the rice pathogenic bacterium Burkholderia glumae 
J. H. HAM (1), R. Chen (1). (1) Dept. Plant Pathology and Crop Physiology, Louisiana State Univ Agric Ctr, Baton Rouge, LA, U.S.A.

<i>Burkholderia glumae </i>is the Gram-negative bacterium causing bacterial panicle blight of rice. Major virulence factors of this pathogen, including toxoflavin (a phytotoxin), lipase and flagella, are known to be controlled by the quorum-sensing (QS) system composed of the LuxI and LuxR homologs, TofI and TofR. Our recent study with <i>B. glumae </i>336gr-1, a virulence strain isolated from a Louisiana rice field, revealed that toxoflavin production can be produced without <i>tofI </i>and/or <i>tofR </i>on a solid medium, implying the presence of unknown cell-to-cell signaling pathways independent of <i>tofI </i>and/or <i>tofR</i>. RNA sequencing and transcriptome analysis with <i>B. glumae </i>QS mutants revealed that genes predicted to function for the synthesis of BDSF (a fatty acid-type QS signaling molecule) and cyclic di-GMP (a key intracellular signaling molecule) as well as for bacterial programmed cell death were expressed in the dependence of the <i>tofI/tofR </i>QS system. In this study, it was also found that many genes involved in signal perception, transduction and transport were up-regulated specifically in the cells grown on a solid medium, suggesting that alternative cell-to-cell signaling pathways are activated in bacterial cells grown in a sessile form.     

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