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Subcellular localization of dinoflagellate polyketide synthases and fatty acid synthase activity
Author(s) -
Van Dolah Frances M.,
Zippay Mackenzie L.,
Pezzolesi Laura,
Rein Kathleen S.,
Johnson Jillian G.,
Morey Jeanine S.,
Wang Zhihong,
Pistocchi Rossella
Publication year - 2013
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/jpy.12120
Subject(s) - biology , chloroplast , dinoflagellate , biochemistry , polyketide , acyl carrier protein , biosynthesis , polyketide synthase , cytosol , enzyme , gene , botany
Dinoflagellates are prolific producers of polyketide secondary metabolites. Dinoflagellate polyketide synthases ( PKS s) have sequence similarity to Type I PKS s, megasynthases that encode all catalytic domains on a single polypeptide. However, in dinoflagellate PKSs identified to date, each catalytic domain resides on a separate transcript, suggesting multiprotein complexes similar to Type II PKS s. Here, we provide evidence through coimmunoprecipitation that single‐domain ketosynthase and ketoreductase proteins interact, suggesting a predicted multiprotein complex. In K arenia brevis (C.C. Davis) Gert Hansen & Ø. Moestrup, previously observed chloroplast localization of PKS s suggested that brevetoxin biosynthesis may take place in the chloroplast. Here, we report that PKS s are present in both cytosol and chloroplast. Furthermore, brevetoxin is not present in isolated chloroplasts, raising the question of what chloroplast‐localized PKS enzymes might be doing. Antibodies to K . brevis PKS s recognize cytosolic and chloroplast proteins in O streopsis cf . ovata Fukuyo, and C oolia monotis Meunier, which produce different suites of polyketide toxins, suggesting that these PKS s may share common pathways. Since PKS s are closely related to fatty acid synthases ( FAS ), we sought to determine if fatty acid biosynthesis colocalizes with either chloroplast or cytosolic PKS s. [ 3 H ]acetate labeling showed fatty acids are synthesized in the cytosol, with little incorporation in chloroplasts, consistent with a Type I FAS system. However, although 29 sequences in a K . brevis expressed sequence tag database have similarity ( BLAST x e ‐value <10 −10 ) to PKS s, no transcripts for either Type I (cytosolic) or Type II (chloroplast) FAS are present. Further characterization of the FAS complexes may help to elucidate the functions of the PKS enzymes identified in dinoflagellates.