title: Novel insights into evolution of protistan polyketide synthases through phylogenomic analysis.
abstract: Polyketide synthase (PKS) enzymes are large multi-domain complexes that structurally and functionally resemble the fatty acid synthases involved in lipid metabolism. Polyketide biosynthesis of secondary metabolites and hence functional PKS genes are widespread among bacteria, fungi and streptophytes, but the Type I was formerly known only from bacteria and fungi. Recently Type I PKS genes were also uncovered in the genomes of some alveolate protists. Here we show that the newly sequenced genomes of representatives of other protist groups, specifically the chlorophytes Ostreococcus tauri, O. lucimarinus, and Chlamydomonas reinhardtii, and the haptophyte Emiliania huxleyi also contain putative modular Type I PKS genes. Based on the patchy phylogenetic distribution of this gene type among eukaryotic microorganisms, the question arises whether they originate from recent lateral gene transfer from bacteria. Our phylogenetic analyses do not indicate such an evolutionary history. Whether Type I PKS genes originated several times independently during eukaryotic evolution or were rather lost in many extant lineages cannot yet be answered. In any case, we show that environmental genome sequencing projects are likely to be a valuable resource when mining for genes resembling protistan PKS I genes.
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany. ujohn@awi-bremerhaven.de
authors.forename: Uwe
authors.initials: U
authors.lastname: John
authors.forename: Bánk
authors.initials: B
authors.lastname: Beszteri
authors.forename: Evelyne
authors.initials: E
authors.lastname: Derelle
authors.forename: Yves
authors.initials: Y
authors.lastname: Van de Peer
authors.forename: Betsy
authors.initials: B
authors.lastname: Read
authors.forename: Hervé
authors.initials: H
authors.lastname: Moreau
authors.forename: Allan
authors.initials: A
authors.lastname: Cembella
mesh_terms: D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000201:enzymology / Q000235:genetics; D000460:Chlorophyta / Q000145:classification / Q000201:enzymology / Q000235:genetics; D019143:Evolution, Molecular; D064429:Fatty Acid Synthases / Q000235:genetics; D023281:Genomics / Q000379:methods*; D010802:Phylogeny; D048630:Polyketide Synthases / Q000235:genetics*
chemical_list: D048630:Polyketide Synthases; D064429:Fatty Acid Synthases