title: Characterisation of the mgo operon in Pseudomonas syringae pv. syringae UMAF0158 that is required for mangotoxin production.
abstract: BACKGROUND
  Mangotoxin is an antimetabolite toxin that is produced by strains of Pseudomonas syringae pv. syringae; mangotoxin-producing strains are primarily isolated from mango tissues with symptoms of bacterial apical necrosis. The toxin is an oligopeptide that inhibits ornithine N-acetyl transferase (OAT), a key enzyme in the biosynthetic pathway of the essential amino acids ornithine and arginine. The involvement of a putative nonribosomal peptide synthetase gene (mgoA) in mangotoxin production and virulence has been reported.
  
  
  RESULTS
  In the present study, we performed a RT-PCR analysis, insertional inactivation mutagenesis, a promoter expression analysis and terminator localisation to study the gene cluster containing the mgoA gene. Additionally, we evaluated the importance of mgoC, mgoA and mgoD in mangotoxin production. A sequence analysis revealed an operon-like organisation. A promoter sequence was located upstream of the mgoB gene and was found to drive lacZ transcription. Two terminators were located downstream of the mgoD gene. RT-PCR experiments indicated that the four genes (mgoBCAD) constitute a transcriptional unit. This operon is similar in genetic organisation to those in the three other P. syringae pathovars for which complete genomes are available (P. syringae pv. syringae B728a, P. syringae pv. tomato DC3000 and P. syringae pv. phaseolicola 1448A). Interestingly, none of these three reference strains is capable of producing mangotoxin. Additionally, extract complementation resulted in a recovery of mangotoxin production when the defective mutant was complemented with wild-type extracts.
  
  
  CONCLUSIONS
  The results of this study confirm that mgoB, mgoC, mgoA and mgoD function as a transcriptional unit and operon. While this operon is composed of four genes, only the last three are directly involved in mangotoxin production.
authors.affiliation: Instituto de Hortofruticultura Subtropical y Mediterránea, Estación Experimental La Mayora, Algarrobo-Costa, Málaga, Spain. arrebolad@eelm.csic.es
authors.forename: Eva
authors.initials: E
authors.lastname: Arrebola
authors.forename: Víctor J
authors.initials: VJ
authors.lastname: Carrión
authors.forename: Francisco M
authors.initials: FM
authors.lastname: Cazorla
authors.forename: Alejandro
authors.initials: A
authors.lastname: Pérez-García
authors.forename: Jesús
authors.initials: J
authors.lastname: Murillo
authors.forename: Antonio
authors.initials: A
authors.lastname: de Vicente
mesh_terms: D019677:Artificial Gene Fusion; D001427:Bacterial Toxins / Q000096:biosynthesis* / Q000235:genetics*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D017930:Genes, Reporter; D005816:Genetic Complementation Test; D031022:Mangifera / Q000382:microbiology; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009876:Operon; D010935:Plant Diseases / Q000382:microbiology; D011401:Promoter Regions, Genetic; D044224:Pseudomonas syringae / Q000235:genetics* / Q000472:pathogenicity*; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013728:Terminator Regions, Genetic; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D001427:Bacterial Toxins; D004269:DNA, Bacterial; D001616:beta-Galactosidase