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Article

Identification of Polyunsaturated Fatty Acids Synthesis Pathways in the Toxic Dinophyte Alexandrium minutum Using 13C-Labelling

1
UMR 6539 LEMAR, CNRS, IRD, Ifremer, University of Brest, F-29280 Plouzané, France
2
Center for Marine Science, Department of Earth and Ocean Sciences, University of North Carolina Wilmington, 5600 Marvin K. Moss Ln., Wilmington, NC 28403, USA
3
Department of Biology, Elon University, 50 Campus Drive, Elon, NC 27244, USA
*
Authors to whom correspondence should be addressed.
Biomolecules 2020, 10(10), 1428; https://doi.org/10.3390/biom10101428
Received: 28 August 2020 / Revised: 26 September 2020 / Accepted: 7 October 2020 / Published: 8 October 2020
(This article belongs to the Special Issue Lipids of Marine Algae)
The synthetic pathways responsible for the production of the polyunsaturated fatty acids 22:6n-3 and 20:5n-3 were studied in the Dinophyte Alexandrium minutum. The purpose of this work was to follow the progressive incorporation of an isotopic label (13CO2) into 11 fatty acids to better understand the fatty acid synthesis pathways in A. minutum. The Dinophyte growth was monitored for 54 h using high-frequency sampling. A. minutum presented a growth in two phases. A lag phase was observed during the first 30 h of development and had been associated with the probable temporary encystment of Dinophyte cells. An exponential growth phase was then observed after t30. A. minutum rapidly incorporated 13C into 22:6n-3, which ended up being the most 13C-enriched polyunsaturated fatty acid (PUFA) in this experiment, with a higher 13C atomic enrichment than 18:4n-3, 18:5n-3, 20:5n-3, and 22:5n-3. Overall, the 13C atomic enrichment (AE) was inversely proportional to number of carbons in n-3 PUFA. C18 PUFAs, 18:4n-3, and 18:5n-3, were indeed among the least 13C-enriched FAs during this experiment. They were assumed to be produced by the n-3 PUFA pathway. However, they could not be further elongated or desaturated to produce n-3 C20-C22 PUFA, because the AEs of the n-3 C18 PUFAs were lower than those of the n-3 C20-C22 PUFAs. Thus, the especially high atomic enrichment of 22:6n-3 (55.8% and 54.9% in neutral lipids (NLs) and polar lipids (PLs), respectively) led us to hypothesize that this major PUFA was synthesized by an O2-independent Polyketide Synthase (PKS) pathway. Another parallel PKS, independent of the one leading to 22:6n-3, was also supposed to produce 20:5n-3. The inverse order of the 13C atomic enrichment for n-3 PUFAs was also suspected to be related to the possible β-oxidation of long-chain n-3 PUFAs occurring during A. minutum encystment. View Full-Text
Keywords: PUFA synthesis; 22:6n-3; DHA; PKS pathway; Dinophyte; Alexandrium minutum; encystment PUFA synthesis; 22:6n-3; DHA; PKS pathway; Dinophyte; Alexandrium minutum; encystment
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MDPI and ACS Style

Remize, M.; Planchon, F.; Loh, A.N.; Le Grand, F.; Lambert, C.; Bideau, A.; Bidault, A.; Corvaisier, R.; Volety, A.; Soudant, P. Identification of Polyunsaturated Fatty Acids Synthesis Pathways in the Toxic Dinophyte Alexandrium minutum Using 13C-Labelling. Biomolecules 2020, 10, 1428. https://doi.org/10.3390/biom10101428

AMA Style

Remize M, Planchon F, Loh AN, Le Grand F, Lambert C, Bideau A, Bidault A, Corvaisier R, Volety A, Soudant P. Identification of Polyunsaturated Fatty Acids Synthesis Pathways in the Toxic Dinophyte Alexandrium minutum Using 13C-Labelling. Biomolecules. 2020; 10(10):1428. https://doi.org/10.3390/biom10101428

Chicago/Turabian Style

Remize, Marine, Frédéric Planchon, Ai N. Loh, Fabienne Le Grand, Christophe Lambert, Antoine Bideau, Adeline Bidault, Rudolph Corvaisier, Aswani Volety, and Philippe Soudant. 2020. "Identification of Polyunsaturated Fatty Acids Synthesis Pathways in the Toxic Dinophyte Alexandrium minutum Using 13C-Labelling" Biomolecules 10, no. 10: 1428. https://doi.org/10.3390/biom10101428

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