title: Effects of growth phase and nitrogen starvation on expression of fatty acid desaturases and fatty acid composition of Isochrysis aff. galbana (TISO).
abstract: Very long-chain polyunsaturated fatty acids (VLC-PUFAs) are important dietary requirements for maintaining human health. Many marine microalgae are naturally high in ω-3 VLC-PUFAs, however, the molecular mechanisms underpinning fatty acid (FA) desaturation and elongation in algae are poorly understood. An advanced molecular understanding would facilitate improvements of this nascent industry. We aimed to investigate expression responses of four front-end fatty acid desaturase genes and downstream effects on FA profiles to nitrogen limitation and cultivation growth stage in Isochrysis aff. galbana (TISO). Cultures were grown in nitrogen-replete and -deplete medium; samples were harvested during logarithmic, late logarithmic and stationary growth phases to analyse FA content/composition and gene expression of ∆(6)-, ∆(8)-, ∆(5)- and ∆(4)-desaturases (d6FAD (putative), d8FAD, d5FAD and d4FAD, respectively). d6FAD (putative) exhibited no differential expression, while d8FAD, d5FAD and d4FAD were significantly upregulated during logarithmic growth of nutrient-replete cultures, coinciding with rapid cell division. In conclusion, it is demonstrated that expression of some FADs in I. aff. galbana varies with culture age and nitrogen status which has downstream consequences on FA desaturation levels. This has implications for the commercial production of VLC-PUFAs where a trade-off between total lipid yield and VLC-PUFAs has to be made.
authors.affiliation: School of Marine and Tropical Biology, James Cook University, Townsville 4811, Australia; Centre for Sustainable Tropical Fisheries and Aquaculture, Townsville 4811, Australia; James Cook University, Comparative Genomics Centre, Townsville, Queensland 4811, Australia.
authors.forename: Roger
authors.initials: R
authors.lastname: Huerlimann
authors.affiliation: School of Marine and Tropical Biology, James Cook University, Townsville 4811, Australia.
authors.forename: Eike J
authors.initials: EJ
authors.lastname: Steinig
authors.affiliation: School of Marine and Tropical Biology, James Cook University, Townsville 4811, Australia.
authors.forename: Heather
authors.initials: H
authors.lastname: Loxton
authors.affiliation: School of Marine and Tropical Biology, James Cook University, Townsville 4811, Australia; Centre for Sustainable Tropical Fisheries and Aquaculture, Townsville 4811, Australia.
authors.forename: Kyall R
authors.initials: KR
authors.lastname: Zenger
authors.affiliation: School of Marine and Tropical Biology, James Cook University, Townsville 4811, Australia; Centre for Sustainable Tropical Fisheries and Aquaculture, Townsville 4811, Australia.
authors.forename: Dean R
authors.initials: DR
authors.lastname: Jerry
authors.affiliation: School of Marine and Tropical Biology, James Cook University, Townsville 4811, Australia; Centre for Sustainable Tropical Fisheries and Aquaculture, Townsville 4811, Australia; James Cook University, Comparative Genomics Centre, Townsville, Queensland 4811, Australia; Centre for Biodiscovery and Molecular Development of Therapeutics, James Cook University, Townsville, Queensland 4811, Australia. Electronic address: kirsten.heimann@jcu.edu.au.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Heimann
mesh_terms: D017756:Aquaculture / Q000379:methods; D018533:Biomass; D044943:Fatty Acid Desaturases / Q000235:genetics* / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry* / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D058087:Haptophyta / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism*; D058086:Microalgae / Q000378:metabolism; D008969:Molecular Sequence Data
chemical_list: D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D044943:Fatty Acid Desaturases
keywords: Docosahexaenoic acid; Human nutrition; Very long-chain polyunsaturated fatty acid