Genome and Transcriptome Analyses Provide Insight Into the Omega-3 Long-Chain Polyunsaturated Fatty Acids Biosynthesis of Schizochytrium limacinum SR21.

Limin Liang,Jiangtao Peng,Xuehai Zheng,Jinmao Zhu,Weiqi Tang,Duo Chen,Wenfang Fan,Ting Xue,Youqiang Chen,Zhen Huang

doi:10.3389/fmicb.2020.00687

Abstract

Schizochytrium sp. is the best natural resource for omega-3 long-chain polyunsaturated fatty acids. We report a high-quality genome sequence of Schizochytrium limacinum SR21, which has a 63 Mb genome size, with a contig N50 of 2.67 Mb and 6,838 protein-coding genes. Phylogenomic and comparative genomic analyses revealed that DHA-producing Schizochytrium and Aurantiochytrium strains were highly similar and possessed similar genes. Analysis of the fatty acid synthase (FAS) for LC-PUFAs production results in the annotation of all genes in map00062 and map01212. A gene cluster and 10 ORFs related to PKS pathway were found in the genome. 1,402 differentially expressed genes (DEGs) of the treated groups (0.5 g/L yeast extract) were identified by comparing with the control groups (1.0 g/L yeast extract) at 36 h. A weighted gene coexpression network analysis revealed that 2 of 7 modules correlated highly with the fatty acid and DHA contents. The DEGs and transcription factors were significantly correlated with fatty acid biosynthesis, including MYB, Zinc Finger and ACOX. The results showed that these hub genes are regulated by genes involved in fatty acid biosynthesis pathways. The results providing an important reference for further research on promoting fatty acid and DHA accumulation in S. limacinum SR21.

Highlights

Schizochytrium sp. is a unicellular fungal-like marine protist found ubiquitously in marine environments and considered as the best natural resource for omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs) (Newell et al, 2019)
All reads from the S. limacinum SR21 genome were assembled into 63 Mb, consisting of 52 contigs
The results indicated that the assembled genome is of good quality (89.1% completeness) (Supplementary Table S5)

Summary

Introduction

Schizochytrium sp. is a unicellular fungal-like marine protist found ubiquitously in marine environments and considered as the best natural resource for omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs) (Newell et al, 2019). Is a unicellular fungal-like marine protist found ubiquitously in marine environments and considered as the best natural resource for omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs) (Newell et al, 2019). The traditional commercial source of DHA is fish oil, which is undesirable because of its offensive. Is considered a noteworthy and satisfactory alternative to fish oil due to the advantages of its fast growth rate, high purity, slight fishy smell, and more than 50% lipid rich in DHA. Many studies have been conducted to optimize the media composition and culture conditions, including nutrient deprivation, strain adaption, temperature shift and genetic engineering to enhance the lipid accumulation efficiency in Schizochytrium sp. Can accumulate lipids up to 50% of its dry weight, with DHA generally constituting 40% or more of the total oils by the above mentioned methods Schizochytrium sp. can accumulate lipids up to 50% of its dry weight, with DHA generally constituting 40% or more of the total oils by the above mentioned methods

Methods

Results

Conclusion