Abstract
Thraustochytrids of the genera Schizochytrium and Aurantiochytrium accumulate oils rich in the essential, marine n3 fatty acid docosahexaenoic acid (DHA). As part of studies of the DHA-production in Aurantiochytrium sp. T66 (ATCC® PRA-276™), the 43 Mbp draft genome was annotated based on ab-initio prediction combined with RNA-Seq mapping. The genome encodes 11683 putative genes, of which functional information could be assigned to 9090. T66 show high sequence similarity to Aurantiochytrium sp. S-3 (ATCC® 26185™), despite the publicly available genome record of S-3 covering only 18.1 Mbp. A global transcriptome analysis was carried out with the aim to provide more knowledge about factors that affect the DHA-productivities and the contributions of the two enzyme systems used for fatty acid synthesis in thraustochytrids, fatty acid synthetase (FAS) and Polyunsaturated fatty acid (PUFA) synthase. Batch cultivation with nitrogen starvation, which is well-known to initiate lipid accumulation in oleaginous organisms, were compared to cultivation with nitrogen in excess, where lipid accumulation was obtained by oxygen limitation. A significant upregulation of FAS under N-deficient conditions was found, while the PUFA-synthase genes were only marginally upregulated. Neither of them was upregulated under O2-limitation where nitrogen was in excess, suggesting that Nstarvation mainly affects the FAS and may be less important for the PUFA-synthase. The transcriptome analysis also revealed responses likely to be related to the generation of reducing power (NADPH) for fatty acid synthesis.