Abstract
In algae, the biosynthesis of docosahexaenoic acid (22:6omega3; DHA) proceeds via the elongation of eicosapentaenoic acid (20:5omega3; EPA) to 22:5omega3, which is required as a substrate for the final Delta4 desaturation. To isolate the elongase specific for this step, we searched expressed sequence tag and genomic databases from the algae Ostreococcus tauri and Thalassiosira pseudonana, from the fish Oncorhynchus mykiss, from the frog Xenopus laevis, and from the sea squirt Ciona intestinalis using as a query the elongase sequence PpPSE1 from the moss Physcomitrella patens. The open reading frames of the identified elongase candidates were expressed in yeast for functional characterization. By this, we identified two types of elongases from O. tauri and T. pseudonana: one specific for the elongation of (Delta6-)C18-PUFAs and one specific for (Delta5-)C20-PUFAs, showing highest activity with EPA. The clones isolated from O. mykiss, X. laevis, and C. intestinalis accepted both C18- and C20-PUFAs. By coexpression of the Delta6- and Delta5-elongases from T. pseudonana and O. tauri, respectively, with the Delta5- and Delta4-desaturases from two other algae we successfully implemented DHA synthesis in stearidonic acid-fed yeast. This may be considered an encouraging first step in future efforts to implement this biosynthetic sequence into transgenic oilseed crops.
Highlights
In algae, the biosynthesis of docosahexaenoic acid (22:63; Docosahexaenoic acid (DHA)) proceeds via the elongation of eicosapentaenoic acid (20:53; EPA) to 22:53, which is required as a substrate for the final ⌬4 desaturation
The majority of elongase sequences available in databases originate from mammals, and among those functionally characterized, none was shown to be specific for the elongation of ⌬6-C18- or ⌬5-C20-PUFAs
The fish O. mykiss, the frog X. laevis, the sea squirt C. intestinalis, and the two DHA-producing algae O. tauri and T. pseudonana were selected as candidate organisms
Summary
The biosynthesis of docosahexaenoic acid (22:63; DHA) proceeds via the elongation of eicosapentaenoic acid (20:53; EPA) to 22:53, which is required as a substrate for the final ⌬4 desaturation. To reconstitute the simpler pathway of DHA biosynthesis, we started experiments to clone a specific C20-PUFA-elongase restricted in its action to a single elongation cycle to produce a C22-PUFA.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.