TY - JOUR T1 - A 13CO2 Enrichment Experiment to Study the Synthesis Pathways of Polyunsaturated Fatty Acids of the Haptophyte Tisochrysis lutea A1 - Remize,Marine A1 - Planchon,Frederic A1 - Garnier,Matthieu A1 - Loh,Ai Ning A1 - Le Grand,Fabienne A1 - Bideau,Antoine A1 - Lambert,Christophe A1 - Corvaisier,Rudolph A1 - Volety,Aswani A1 - Soudant,Philippe AD - UMR 6539 LEMAR, CNRS, IRD, Ifremer, University of Brest, 29280 Plouzane, France AD - GREENSEA, Promenade du Sergeant Navarro, 34140 Meze, France AD - PBA, Ifremer, Rue de l’Ile d’Yeu, BP 21105, CEDEX 03, 44311 Nantes, France AD - Center for Marine Science, Department of Earth and Ocean Sciences, University of North Carolina Wilmington, 5600 Marvin K. Moss Ln, Wilmington, NC 28403, USA AD - 50 Campus Drive, Elon University, Elon, NC 27244, USA AD - UMR 6539 LEMAR, CNRS, IRD, Ifremer, University of Brest, 29280 Plouzane, France UR - https://archimer.ifremer.fr/doc/00742/85353/ DO - 10.3390/md20010022 KW - long-chain PUFA synthesis KW - desaturases KW - elongases KW - PKS pathway KW - 20 KW - 5n-3 (EPA) KW - 22 KW - 6n-3 (DHA) KW - Tisochrysis lutea KW - C-13 artificial enrichment N2 - The production of polyunsaturated fatty acids (PUFA) in Tisochrysis lutea was studied using the gradual incorporation of a 13C-enriched isotopic marker, 13CO2, for 24 h during the exponential growth of the algae. The 13C enrichment of eleven fatty acids was followed to understand the synthetic pathways the most likely to form the essential polyunsaturated fatty acids 20:5n-3 (EPA) and 22:6n-3 (DHA) in T. lutea. The fatty acids 16:0, 18:1n-9 + 18:3n-3, 18:2n-6, and 22:5n-6 were the most enriched in 13C. On the contrary, 18:4n-3 and 18:5n-3 were the least enriched in 13C after long chain polyunsaturated fatty acids such as 20:5n-3 or 22:5n-3. The algae appeared to use different routes in parallel to form its polyunsaturated fatty acids. The use of the PKS pathway was hypothesized for polyunsaturated fatty acids with n-6 configuration (such as 22:5n-6) but might also exist for n-3 PUFA (especially 20:5n-3). With regard to the conventional n-3 PUFA pathway, Δ6 desaturation of 18:3n-3 appeared to be the most limiting step for T. lutea, “stopping” at the synthesis of 18:4n-3 and 18:5n-3. These two fatty acids were hypothesized to not undergo any further reaction of elongation and desaturation after being formed and were therefore considered “end-products”. To circumvent this limiting synthetic route, Tisochrysis lutea seemed to have developed an alternative route via Δ8 desaturation to produce longer chain fatty acids such as 20:5n-3 and 22:5n-3. 22:6n-3 presented a lower enrichment and appeared to be produced by a combination of different pathways: the conventional n-3 PUFA pathway by desaturation of 22:5n-3, the alternative route of ω-3 desaturase using 22:5n-6 as precursor, and possibly the PKS pathway. In this study, PKS synthesis looked particularly effective for producing long chain polyunsaturated fatty acids. The rate of enrichment of these compounds hypothetically synthesized by PKS is remarkably fast, making undetectable the 13C incorporation into their precursors. Finally, we identified a protein cluster gathering PKS sequences of proteins that are hypothesized allowing n-3 PUFA synthesis. Y1 - 2022/01 PB - MDPI AG JF - Marine Drugs SN - 1660-3397 VL - 20 IS - 1 ID - 85353 ER -