title: Role of Modular Polyketide Synthases in the Production of Polyether Ladder Compounds in Ciguatoxin-Producing Gambierdiscus polynesiensis and G. excentricus (Dinophyceae).
abstract: Gambierdiscus, a benthic dinoflagellate, produces ciguatoxins that cause the human illness Ciguatera. Ciguatoxins are polyether ladder compounds that have a polyketide origin, indicating that polyketide synthases (PKS) are involved in their production. We sequenced transcriptomes of Gambierdiscus excentricus and Gambierdiscus polynesiensis and found 264 contigs encoding single domain ketoacyl synthases (KS; G. excentricus: 106, G. polynesiensis: 143) and ketoreductases (KR; G. excentricus: 7, G. polynesiensis: 8) with sequence similarity to type I PKSs, as reported in other dinoflagellates. In addition, 24 contigs (G. excentricus: 3, G. polynesiensis: 21) encoding multiple PKS domains (forming typical type I PKSs modules) were found. The proposed structure produced by one of these megasynthases resembles a partial carbon backbone of a polyether ladder compound. Seventeen contigs encoding single domain KS, KR, s-malonyltransacylase, dehydratase and enoyl reductase with sequence similarity to type II fatty acid synthases (FAS) in plants were found. Type I PKS and type II FAS genes were distinguished based on the arrangement of domains on the contigs and their sequence similarity and phylogenetic clustering with known PKS/FAS genes in other organisms. This differentiation of PKS and FAS pathways in Gambierdiscus is important, as it will facilitate approaches to investigating toxin biosynthesis pathways in dinoflagellates.
authors.affiliation: Climate Change Cluster, University of Technology Sydney, Ultimo, NSW, 2007, Australia.|Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, 689528, Singapore.
authors.forename: Gurjeet S
authors.identifier: 0000-0002-4578-2355
authors.initials: GS
authors.lastname: Kohli
authors.affiliation: Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, David Keir Building, Stranmillis Road, Belfast, BT9 5AG, United Kingdom.
authors.forename: Katrina
authors.initials: K
authors.lastname: Campbell
authors.affiliation: Alfred-Wegener-Institute Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, 27515, Germany.|Helmholtz Institute for Functional Marine Biodiversity, University of Oldenburg, Oldenburg, 26111, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: John
authors.affiliation: Cawthron Institute, 98 Halifax Street East, Nelson, 7010, New Zealand.
authors.forename: Kirsty F
authors.initials: KF
authors.lastname: Smith
authors.affiliation: Instituto Español de Oceanografía, Centro Oceanográfico de Vigo, Subida a Radio Faro 50, Vigo, 36390, Spain.
authors.forename: Santiago
authors.initials: S
authors.lastname: Fraga
authors.affiliation: Cawthron Institute, 98 Halifax Street East, Nelson, 7010, New Zealand.
authors.forename: Lesley L
authors.initials: LL
authors.lastname: Rhodes
authors.affiliation: Climate Change Cluster, University of Technology Sydney, Ultimo, NSW, 2007, Australia.
authors.forename: Shauna A
authors.initials: SA
authors.lastname: Murray
mesh_terms: D000595:Amino Acid Sequence; D053898:Biosynthetic Pathways; D002922:Ciguatoxins / Q000378:metabolism*; D004141:Dinoflagellida / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D064429:Fatty Acid Synthases / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D020869:Gene Expression Profiling / Q000379:methods*; D015971:Gene Expression Regulation, Enzymologic; D008958:Models, Molecular; D010802:Phylogeny; D048630:Polyketide Synthases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA / Q000379:methods*; D017386:Sequence Homology, Amino Acid
chemical_list: D005227:Fatty Acids; D015800:Protozoan Proteins; D002922:Ciguatoxins; D048630:Polyketide Synthases; D064429:Fatty Acid Synthases
keywords: Biosynthesis; fatty acid synthase