Physical and functional analyses of the syrA and syrB genes involved in syringomycin production by Pseudomonas syringae pv. syringae

• Published in: Journal of Bacteriology 1988-12, Vol.170 (12), p.5680-5688
• Main Authors: Xu, G.W, Gross, D.C
• Format: Article
• Language: English
• Subjects: Bacterial plant pathogens; Bacterial Proteins - genetics; Bacteriology; Biological and medical sciences; BIOSINTESIS; BIOSYNTHESE; Cloning, Molecular; Cosmids; DNA Transposable Elements; Fundamental and applied biological sciences. Psychology; GENE; GENES; Genetic Vectors; GENETICA; Genetics; GENETIQUE; Genotype; Microbiology; Mutation; Phytopathology. Animal pests. Plant and forest protection; Plants - microbiology; Plasmids; PODER PATOGENO; POUVOIR PATHOGENE; PSEUDOMONAS; Pseudomonas - genetics; Pseudomonas - pathogenicity; Pseudomonas syringae; Pseudomonas syringae syringae; Restriction Mapping; Systematics. Structure, properties and multiplication. Genetics; TOXINAS; TOXINE
• ISSN: 0021-9193; 1098-5530; 1067-8832
• DOI: 10.1128/jb.170.12.5680-5688.1988

The syrA and syrB genes involved in syringomycin production in Pseudomonas syringae pv. syringae B301D were identified from an EcoRI-pLAFR3 cosmid library and then physically and functionally analyzed in relation to plant pathogenicity. Homologous recombination of the genes required for syringomycin production from cosmids pGX183 (syrA) and pGX56 (syrB), respectively, introduced into nontoxigenic (Tox(-)) Tn5 mutants W4S2545 and W4S770 resulted in the concomitant restoration of toxin production and full virulence. The disease indices of the Tox(+) strains obtained by recombination of the cloned, homologous DNA into the corresponding Tn5 mutant were essentially equivalent to that of strain B301D-R and significantly higher than those of W4S2545 and W4S770. A 12-kilobase (kb) EcoRI fragment from pGX183 was subcloned (i.e., pGX15) and found to contain the sequences necessary for syringomycin production. A map of pGX15 prepared by a combination of restriction endonuclease digestions and Tn5 mutagenesis showed that the syrA sequence was 2.3 to 2.8 kb. Marker exchange of syrA::Tn5 from pGX15 into B301D-R yielded nonpathogenic phenotypes, indicating that syrA is a regulatory gene since it is necessary for both syringomycin production and pathogenicity. The 4.9-kb EcoRI fragment from pGX56 was subcloned (i.e., pGX4) and shown to carry the syrB sequence which was 2.4 to 3.3 kb. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of protein extracts from B301D-R associated five proteins, ranging from equivalent to 130,000 to equivalent to 470,000 in molecular weight, with syringomycin production. The syrA and syrB genes were required for the formation of proteins SR4 (equivalent to 350,000) and SR5 (equivalent to (130,000), which are believed to be components of the syringomycin synthetase complex