γ-Resorcylate Catabolic-Pathway Genes in the Soil Actinomycete Rhodococcus jostii RHA1

TheRhodococcus jostii RHA1 gene cluster required for γ-resorcylate (GRA) catabolism was characterized. The cluster includestsdA ,tsdB ,tsdC ,tsdD ,tsdR ,tsdT , andtsdX , which encode GRA decarboxylase, resorcinol 4-hydroxylase, hydroxyquinol 1,2-dioxygenase, maleylacetate reductase, an IclR-type regulator, a major facilitator superfamily transporter, and a putative hydrolase, respectively. ThetsdA gene conferred GRA decarboxylase activity onEscherichia coli . Purified TsdB oxidized NADH in the presence of resorcinol, suggesting thattsdB encodes a unique NADH-specific single-component resorcinol 4-hydroxylase. Mutations in eithertsdA ortsdB resulted in growth deficiency on GRA. ThetsdC andtsdD genes conferred hydroxyquinol 1,2-dioxygenase and maleylacetate reductase activities, respectively, onE. coli . Inactivation oftsdT significantly retarded the growth of RHA1 on GRA. The growth retardation was partially suppressed under acidic conditions, suggesting the involvement oftsdT in GRA uptake. Reverse transcription-PCR analysis revealed that thetsd genes constitute three transcriptional units, thetsdBADC andtsdTX operons andtsdR . Transcription of thetsdBADC andtsdTX operons was induced during growth on GRA. Inactivation oftsdR derepressed transcription of thetsdBADC andtsdTX operons in the absence of GRA, suggesting thattsd gene transcription is negatively regulated by thetsdR -encoded regulator. Binding of TsdR to thetsdR-tsdB andtsdT-tsdR intergenic regions was inhibited by the addition of GRA, indicating that GRA interacts with TsdR as an effector molecule.