title: A gene for a dioxygenase-like protein determines the production of the DF signal in Xanthomonas campestris pv. campestris.
abstract: SUMMARY The DF signal molecule regulates the production of both yellow pigments (xanthomonadins) and extracellular polysaccharide (EPS) in Xanthomonas campestris pv. campestris. These two bacterial products are crucial to the epiphytic survival and pathogenicity of this pathogen on its plant hosts. Previous work suggested that DF is a butyrolactone, which the Streptomyces bacteria are known to utilize as signals. pigB is one of seven transcriptional units in the X. c. pv. campestris xanthomonadin gene cluster, and its inactivation results in the loss of DF signal, xanthomonadin and EPS production. Here, determination and analysis of the pigB DNA sequence reveals the presence of two open reading frames, the first (xanB1) encoding a putative reductase/halogenase, and the second (xanB2) showing the highest level of identity to Streptomyces genes encoding putative pteridine-dependent dioxygenase-like proteins. We show that xanB2 (but not xanB1) is needed for production of the DF signal, and that some Streptomyces strains produce functional analogues of DF. A role for xanB2 in the biosynthesis of DF is proposed.
authors.affiliation: Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow, Idaho 83844-2339, USA.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Poplawsky
authors.forename: Dana M
authors.initials: DM
authors.lastname: Walters
authors.forename: Pierre E
authors.initials: PE
authors.lastname: Rouviere
authors.forename: Wesley
authors.initials: W
authors.lastname: Chun