| Abstract | Very long-chain polyunsaturated fatty acids (VLCPUFAs) areessential components of cell membranes and precursors forbioactive compounds regulating important physiological pro-cesses in humans and animals. Lack or imbalance of these fattyacids can lead to various physiological problems in humans suchas immunological disorders, neurological conditions and cardio-vascular diseases (Bazinet and Laye,2014). The current marketand transgenic plant production of VLCPUFAs is primarily focusedon twoω3 VLCPUFAs, docosahexaenoic acid (DHA, 22:6n-3),eicosapentaenoic acid (EPA, 20:5n-3), while other VLCPUFAshave been overlooked (Ganesh and Hettiarachchy,2016; Napieret al.,2019; Qiuet al.,2020). Docosatrienoic acid (DTA, 22:3n-3) is anω3 VLCPUFA with 22 carbons and three double bonds at13, 16 and 19 positions, and was recently found to possess anti-inflammatory and antitumor properties comparable to DHA withpotential nutraceutical and cosmetic uses (Chenet al.,2021).Biosynthesis of DTA follows the elongation and desaturationpathways ofω6 andω3 polyunsaturated fatty acids (PUFAs;Figure1a). In theω3 pathway,a-linolenic acid (ALA, 18:3n-3) iselongated to eicosatrienoic acid (ETA, 20:3n-3) which is thenelongated again to DTA (22:3n-3) by a single ELO type elongase(EhELO1) (Meesapyodsuket al.,2018). In theω6 pathway,linoleic acid (LA, 18:2n-6) is elongated to eicosadienoic acid(EDA, 20:2n-6) and elongated again to docosadienoic acid (DDA,22:2n-6) by the same elongase. In addition, LA can be desatu-rated to ALA by a 18C-PUFAω3 desaturase (CpDesX) while EDAcan also be desaturated to ETA by a VLCPUFAω3 desaturase(PiO3). Both desaturated products, ALA and ETA, can then beelongated to DTA by EhELO |
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