Low-temperature effects on docosahexaenoic acid biosynthesis in Schizochytrium sp. TIO01 and its proposed underlying mec
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Biotechnology for Biofuels Open Access
RESEARCH
Low‑temperature effects on docosahexaenoic acid biosynthesis in Schizochytrium sp. TIO01 and its proposed underlying mechanism Fan Hu1 , April L. Clevenger2, Peng Zheng3, Qiongye Huang1 and Zhaokai Wang1*
Abstract Background: Schizochytrium species are known for their abundant production of docosahexaenoic acid (DHA). Low temperatures can promote the biosynthesis of polyunsaturated fatty acids (PUFAs) in many species. This study investigates low-temperature effects on DHA biosynthesis in Schizochytrium sp. TIO01 and its underlying mechanism. Results: The Schizochytrium fatty acid biosynthesis pathway was evaluated based on de novo genome assembly (contig N50 = 2.86 Mb) and iTRAQ-based protein identification. Our findings revealed that desaturases, involved in DHA synthesis via the fatty acid synthase (FAS) pathway, were completely absent. The polyketide synthase (PKS) pathway and the FAS pathway are, respectively, responsible for DHA and saturated fatty acid synthesis in Schizochytrium. Analysis of fatty acid composition profiles indicates that low temperature has a significant impact on the production of DHA in Schizochytrium, increasing the DHA content from 43 to 65% of total fatty acids. However, the expression levels of PKS pathway genes were not significantly regulated as the DHA content increased. Further, gene expression analysis showed that pathways related to the production of substrates (acetyl-CoA and NADPH) for fatty acid synthesis (the branched-chain amino acid degradation pathway and the pentose phosphate pathway) and genes related to saturated fatty acid biosynthesis (the FAS pathway genes and malic enzyme) were, respectively, upregulated and downregulated. These results indicate that low temperatures increase the DHA content by likely promoting the entry of relatively large amounts of substrates into the PKS pathway. Conclusions: In this study, we provide genomic, proteomic, and transcriptomic evidence for the fatty acid synthesis pathway in Schizochytrium and propose a mechanism by which low temperatures promote the accumulation of DHA in Schizochytrium. The high-quality and nearly complete genome sequence of Schizochytrium provides a valuable reference for investigating the regulation of polyunsaturated fatty acid biosynthesis and the evolutionary characteristics of Thraustochytriidae species. Keywords: Low temperature, Polyunsaturated fatty acid, Schizochytrium, De novo genome assembly, Differential expressed genes
*Correspondence: [email protected] 1 Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China Full list of author information is available at the end of the article
Background Docosahexaenoic acid (DHA, C22:6), a major ω-3 polyunsaturated fatty acid (PUFA), is widely distributed among phospholipids in the human brain and retina, playing a vital role in human health [1]. A variety of marine microorganisms are rich in DHA [2, 3]. As one
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