The Contribution of Syringopeptin and Syringomycin to Virulence of Pseudomonas syringae pv. syringae strain B301D on the Basis of sypA and syrB1 Biosynthesis Mutant Analysis

Abstract

Sequencing of an approximately 3.9-kb fragment downstream of the syrD gene of Pseudomonas syringae pv. syringae strain B301D revealed that this region, designated sypA, codes for a peptide synthetase, a multifunctional enzyme involved in the thiotemplate mechanism of peptide biosynthesis. The translated protein sequence encompasses a complete amino acid activation module containing the conserved domains characteristic of peptide synthetases. Analysis of the substrate specificity region of this module indicates that it incorporates 2,3-dehydroaminobutyric acid into the syringopeptin peptide structure. Bioassay and high performance liquid chromatography data confirmed that disruption of the sypA gene in strain B301D resulted in the loss of syringopeptin production. The contribution of syringopeptin and syringomycin to the virulence of P. syringae pv. syringae strain B301D was examined in immature sweet cherry with sypA and syrB1 synthetase mutants defective in the production of the two toxins, respectively. Syringopeptin (sypA) and syringomycin (syrB1) mutants were reduced in virulence 59 and 26%, respectively, compared with the parental strain in cherry, whereas the syringopeptin-syringomycin double mutant was reduced 76% in virulence. These data demonstrate that syringopeptin and syringomycin are major virulence determinants of P. syringae pv. syringae.

Indole-3-Acetic Acid Biosynthesis Is Deficient in Gluconacetobacter diazotrophicus Strains with Mutations in Cytochrome c Biogenesis Genes

“…The Tn5-linked region of MAd10 was cloned and sequenced; it encoded gene products with a high similarity to several antibiotic synthetase enzymes from Bacillus subtilis, Streptomyces sp., and Pseudomonas sp. (27,29,39). This result suggested that the IAA Ϫ phenotype of MAd10 was not linked to the Tn5 insertion site.…”

Characterization of the Transcriptional Activators SalA and SyrF, Which Are Required for Syringomycin and Syringopeptin Production byPseudomonas syringaepv. syringae

“…All of the constructs were verified by DNA sequencing with appropriate primers. B301D cells were transformed with pNWSalANE and pNWSyrFNE in order to test the effects of SalA or SyrF overexpression on syringomycin production with a standard bioassay, as described previously (61). Additionally, constructs pNWSalANE and pNWSyrFNE were transformed separately into B301DSL8 and B301DSL29 to test the effect of overexpression of the N-terminal regions of SalA and SyrF on GUS activities of the syrB1::uidA and sypA::uidA reporters.…”

Cyclic Lipopeptide Surfactant Production by Pseudomonas fluorescens SS101 Is Not Required for Suppression of Complex Pythium spp. Populations

“…communities Cyclic lipopeptides (CLPs) are produced by a diversity of bacterial genera and have been implicated in a multiplicity of functions among producing strains (11,24,26,28,29). For certain plant-pathogenic bacteria such as Pseudomonas syringae, these compounds may function as virulence determinants, though disease may still develop in their absence (2,30). CLPs have been shown to possess a role in antagonistic interactions between producing strains and other organisms, including bacteria, fungi, and viruses (28).…”