Comparative Transcriptomic Analysis Uncovers Genes Responsible for the DHA Enhancement in the Mutant Aurantiochytrium sp.

Liangxu Liu,Chuhan Lv,Huapu Chen,Zhangli Hu,Madiha Zaynab,Xuewei Yang,Christopher H K Cheng,Hao Yang,Shuangfei Li,Siting Li

doi:10.3390/microorganisms8040529

Liangxu Liu, Chuhan Lv + Show 8 more

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https://doi.org/10.3390/microorganisms8040529

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Abstract

Docosahexaenoic acid (DHA), a n-3 long-chain polyunsaturated fatty acid, is critical for physiological activities of the human body. Marine eukaryote Aurantiochytrium 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 Aurantiochytrium 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 Aurantiochytrium 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 CoAT, AT, ER, DH, and MT down-regulated in wild type but up-regulated in mutant strain X2, corresponding to the increased intercellular DHA accumulation. These findings indicated that CoAT, AT, ER, DH, and MT can be exploited for high DHA yields in Aurantiochytrium.

Highlights

Owing to the importance of cell membrane function and numerous cellular processes for maintaining health, long-chain polyunsaturated fatty acids (LC-PUFAs) have attracted increasing attention for human health
UV radiation has been widely used in the breeding of microbial species [49], but rarely used in the production of docosahexaenoic acid (DHA) by Aurantiochytrium sp
Biochemical studies have been performed to characterize the distinct enzymes from the standard polyketide synthase (PKS) pathways, which is helpful for understanding the underlying biosynthetic mechanisms [79]. These findings revealed that the fatty acid synthesis (FAS) pathway does not participate in the biosynthesis of DHA in the Aurantiochytrium sp. strain

Summary

Introduction

Owing to the importance of cell membrane function and numerous cellular processes for maintaining health, long-chain polyunsaturated fatty acids (LC-PUFAs) have attracted increasing attention for human health. LC-PUFAs can be classified into two principal families, namely, omega-3 (n-3) and omega-6 (n-6) fatty acids (FAs) [1]. The typical n-3 LC-PUFAs are docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which can strongly influence monocyte physiology. Fatty fish including sardines [6], Oncorhynchus keta [7], Thunnus [8], etc. Is being used as the primary global supply for DHA [9]. Marine microalgae including chrysophyta [12], dinoflagellate [13], and diatom [14], are regarded as a promising alternative as the primary producer of the EPA and DHA in marine food webs

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