Genetic and Transcriptomic Analyses of the Rice Pathogenic Bacterium, Burkholderia glumae, Reveal the Important Roles of the Regulatory Gene, tepR, for Bacterial Survival in Environmental Stresses

Abstract

Burkholderia glumae causes bacterial panicle blight in rice by producing the phytotoxin, toxoflavin, as a major virulence factor. Production of toxoflavin is negatively regulated by tepR, which encodes a sigma 54-dependent response regulator. In order to gain insights into the comprehensive biological functions of tepR, the genome-wide transcriptional profile dependent on tepR was analyzed through comparative transcriptome analysis between a tepR defective mutant and the wild-type strain, resulting in the identification of 238 differentially expressed genes (DEGs). Gene Ontology (GO) enrichment analysis indicated that genes involved in flagella assembly and stress response were highly enriched in tepR defective strain. Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment further revealed that tepR positively regulates the gene cluster encoding a type six secretion system (T6SS) and the genes for a branched-chain amino acid ABC Transporter system, but negatively regulates the genes for thiamine, cysteine and methionine metabolism. As homologues of tepR are found in a number of pathogenic Burkholderia species, the modulation of bacterial behavior through the regulatory action of tepR is likely to be a widely occurring phenomenon in this group of bacterial pathogen.