title: Phylogenetic evidence for the early evolution of microcystin synthesis.
abstract: Cyanobacteria are a prolific source of secondary metabolites, including compounds with toxic and enzyme-inhibiting activities. Microcystins and nodularins are the end products of a secondary metabolic pathway comprised of mixed polyketide synthases and nonribosomal peptide synthetases. Both peptides are potent natural toxins produced by distantly related genera of cyanobacteria. Horizontal gene transfer is thought to play a role in the sporadic distribution of microcystin producers among cyanobacteria. Our phylogenetic analyses indicate a coevolution of housekeeping genes and microcystin synthetase genes for the entire evolutionary history of the toxin. Hence they do not corroborate horizontal transfer of genes for microcystin biosynthesis between the genera. The sporadic distribution of microcystin synthetase genes in modern cyanobacteria suggests that the ability to produce the toxin has been lost repeatedly in the more derived lineages of cyanobacteria. The data we present here strongly suggest that the genes encoding nodularin synthetase are recently derived from those encoding microcystin synthetase.
authors.affiliation: Department of Applied Chemistry and Microbiology, University of Helsinki, P.O. Box 56, Viikki Biocenter, Viikinkaari 9, FIN-00014, Helsinki, Finland.
authors.forename: Anne
authors.initials: A
authors.lastname: Rantala
authors.forename: David P
authors.initials: DP
authors.lastname: Fewer
authors.forename: Michael
authors.initials: M
authors.lastname: Hisbergues
authors.forename: Leo
authors.initials: L
authors.lastname: Rouhiainen
authors.forename: Jaana
authors.initials: J
authors.lastname: Vaitomaa
authors.forename: Thomas
authors.initials: T
authors.lastname: Börner
authors.forename: Kaarina
authors.initials: K
authors.lastname: Sivonen
mesh_terms: D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D052998:Microcystins; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000096:biosynthesis*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D052998:Microcystins; D010456:Peptides, Cyclic; D012336:RNA, Ribosomal, 16S; C078588:microcystin; C108570:beta' subunit of RNA polymerase; D012321:DNA-Directed RNA Polymerases