title: The effect of nitrogen limitation on acetyl-CoA carboxylase expression and fatty acid content in Chromera velia and Isochrysis aff. galbana (TISO).
abstract: Lipids from microalgae have become a valuable product with applications ranging from biofuels to human nutrition. While changes in fatty acid (FA) content and composition under nitrogen limitation are well documented, the involved molecular mechanisms are poorly understood. Acetyl-CoA carboxylase (ACCase) is a key enzyme in the FA synthesis and elongation pathway. Plastidial and cytosolic ACCases provide malonyl-CoA for de novo FA synthesis in the plastid and FA elongation in the endoplasmic reticulum, respectively. The present study aimed at investigating the expression of plastidial and cytosolic ACCase in Chromera velia and Isochrysis aff. galbana (TISO) and their impact on FA content and elongation level when grown under nitrogen-deplete conditions. In C. velia, plastidial ACCase was significantly upregulated during nitrogen starvation and with culture age, strongly correlating with increased FA content. Conversely, plastidial ACCase of I. aff. galbana was not differentially expressed in nitrogen-deplete cultures, but upregulated during the logarithmic phase of nitrogen-replete cultures. In contrast to plastidial ACCase, the cytosolic ACCase of C. velia was downregulated with culture age and nitrogen-starvation, strongly correlating with an increase in medium-chain FAs. In conclusion, the expression of plastidial and cytosolic ACCase changed with growth phase and nutrient status in a species-specific manner and nitrogen limitation did not always result in FA accumulation.
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: D000103:Acetyl-CoA Carboxylase / Q000235:genetics*; D056893:Alveolata / Q000235:genetics* / Q000378:metabolism; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D058087:Haptophyta / Q000235:genetics* / Q000378:metabolism; D009584:Nitrogen / Q000172:deficiency*
chemical_list: D005227:Fatty Acids; D000103:Acetyl-CoA Carboxylase; D009584:Nitrogen
keywords: Cytosolic; Differential expression; Elongation; Homomeric; Plastidial