In:
Journal of Phycology, Wiley, Vol. 49, No. 6 ( 2013-12), p. 1118-1127
Abstract:
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.
Type of Medium:
Online Resource
ISSN:
0022-3646
,
1529-8817
DOI:
10.1111/jpy.2013.49.issue-6
Language:
English
Publisher:
Wiley
Publication Date:
2013
detail.hit.zdb_id:
281226-5
detail.hit.zdb_id:
1478748-9
SSG:
12
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