Comparative Transcriptomic Analysis Uncovers Genes Responsible for the DHA Enhancement in the Mutant <i>Aurantiochytrium</i> sp.

• Main Authors: Liangxu Liu, Zhangli Hu, Shuangfei Li, Hao Yang, Siting Li, Chuhan Lv, Madiha Zaynab, Christopher H. K. Cheng, Huapu Chen, Xuewei Yang
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Microorganisms
• Subjects: Docosahexaenoic acid (DHA); polyunsaturated fatty acids (PUFAs); mutant strain; <i>Aurantiochytrium</i> sp.; transcriptome
• Online Access: https://www.mdpi.com/2076-2607/8/4/529

Docosahexaenoic acid (DHA), a <i>n</i>-3 long-chain polyunsaturated fatty acid, is critical for physiological activities of the human body. Marine eukaryote <i>Aurantiochytrium</i> sp. is considered a promising source for DHA production. Mutational studies have shown that ultraviolet (UV) irradiation (50 W, 30 s) could be utilized as a breeding strategy for obtaining high-yield DHA-producing <i>Aurantiochytrium</i> sp. After UV irradiation (50 W, 30 s), the mutant strain X2 which shows enhanced lipid (1.79-fold, 1417.37 mg/L) and DHA (1.90-fold, 624.93 mg/L) production, was selected from the wild <i>Aurantiochytrium</i> sp. Instead of eicosapentaenoic acid (EPA), 9.07% of docosapentaenoic acid (DPA) was observed in the mutant strain X2. The comparative transcriptomic analysis showed that in both wild type and mutant strain, the fatty acid synthesis (FAS) pathway was incomplete with key desaturases, but genes related to the polyketide synthase (PKS) pathway were observed. Results presented that mRNA expression levels of <i>CoAT, AT, ER, DH,</i> and <i>MT</i> down-regulated in wild type but up-regulated in mutant strain X2, corresponding to the increased intercellular DHA accumulation. These findings indicated that <i>CoAT</i>, <i>AT</i>, <i>ER</i>, <i>DH</i>, and <i>MT</i> can be exploited for high DHA yields in <i>Aurantiochytrium</i>.