Phylogenetic evidence for the early evolution of microcystin synthesis.
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.
Rantala
Anne
A
Department of Applied Chemistry and Microbiology, University of Helsinki, P.O. Box 56, Viikki Biocenter, Viikinkaari 9, FIN-00014, Helsinki, Finland.
Fewer
David P
DP
Hisbergues
Michael
M
Rouhiainen
Leo
L
Vaitomaa
Jaana
J
Börner
Thomas
T
Sivonen
Kaarina
K
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
D052998:Microcystins; D010456:Peptides, Cyclic; D012336:RNA, Ribosomal, 16S; C078588:microcystin; C108570:beta' subunit of RNA polymerase; D012321:DNA-Directed RNA Polymerases