Albicidin pathotoxin produced by Xanthomonas albilineans is encoded by three large PKS and NRPS genes present in a gene cluster also containing several putative modifying, regulatory, and resistance genes.
Xanthomonas albilineans, which causes leaf scald disease of sugarcane, produces a highly potent pathotoxin called albicidin. We report here sequencing and homology analysis of the major gene cluster, XALB1 (55,839 bp), and a second, smaller region, XALB2 (2,986 bp), involved in albicidin biosynthesis. XALB1 contains 20 open reading frames, including i) three large genes with a modular architecture characteristic of polyketide synthases (PKSs) and nonribosomal peptide synthases (NRPSs) and ii) several putative modifying, regulatory, and resistance genes. Sequencing and complementation studies of six albicidin-defective mutants enabled us to confirm the involvement of the three PKS and NRPS genes encoded by XALB1 in albicidin production. XALB2 contains only one gene that is required for post-translational activation of PKS and NRPS enzymes, confirming the involvement of these enzymes in albicidin biosynthesis. In silico analysis of these three PKS or NRPS enzymes allowed us to propose a model for the albicidin backbone assembly and to gain insight into the structural features of this pathotoxin. This is the first description of a complete mixed PKS-NRPS gene cluster for toxin production in the genus Xanthomonas.
Royer
Monique
M
UMR 385 CIRAD/ENSAM/INRA Biologie et Génétique des Interactions Plante-Parasite, Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Campus International de Baillarguet, TA 41/K, 34398 Montpellier Cedex 5, France.
Costet
Laurent
L
Vivien
Eric
E
Bes
Martine
M
Cousin
Arnaud
A
Damais
Anne
A
Pieretti
Isabelle
I
Savin
Alexandre
A
Megessier
Sandrine
S
Viard
Magali
M
Frutos
Roger
R
Gabriel
Dean W
DW
Rott
Philippe C
PC
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D005810:Multigene Family; D009154:Mutation; D009930:Organic Chemicals; D010453:Peptide Synthases / Q000235:genetics*; D010935:Plant Diseases / Q000382:microbiology; D031786:Saccharum / Q000382:microbiology; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014974:Xanthomonas / Q000201:enzymology* / Q000235:genetics* / Q000472:pathogenicity
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D009097:Multienzyme Complexes; D009930:Organic Chemicals; C046156:albicidin; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase