Enhanced accumulation of oil through co-expression of fatty acid and ABC transporters in Chlamydomonas under standard growth conditions

Ru Chen; Miao Yang; Mengjie Li; Hao Zhang; Han Lu; Xiaotan Dou; Shiqi Feng; Song Xue; Chenba Zhu; Zhanyou Chi; Fantao Kong

doi:10.1186/s13068-022-02154-6

Enhanced accumulation of oil through co-expression of fatty acid and ABC transporters in Chlamydomonas under standard growth conditions

Biotechnol Biofuels Bioprod. 2022 May 20;15(1):54. doi: 10.1186/s13068-022-02154-6.

Authors

Ru Chen^#¹, Miao Yang^#^{1

2}, Mengjie Li¹, Hao Zhang¹, Han Lu¹, Xiaotan Dou¹, Shiqi Feng¹, Song Xue¹, Chenba Zhu³, Zhanyou Chi¹, Fantao Kong⁴

Affiliations

¹ School of Bioengineering, Dalian University of Technology, Dalian, 116024, China.
² School of Life Science, Ganjingzi District, Liaoning Normal University, No. 1, Liushu South Street, Dalian, 116081, China.
³ Institute of Biotechnology, RWTH Aachen University, Worringerweg 3, 52074, Aachen, Germany.
⁴ School of Bioengineering, Dalian University of Technology, Dalian, 116024, China. kongfantao@dlut.edu.cn.

^# Contributed equally.

Abstract

Background: Chloroplast and endoplasmic reticulum (ER)-localized fatty acid (FA) transporters have been reported to play important roles in oil (mainly triacylglycerols, TAG) biosynthesis. However, whether these FA transporters synergistically contribute to lipid accumulation, and their effect on lipid metabolism in microalgae are unknown.

Results: Here, we co-overexpressed two chloroplast-localized FA exporters (FAX1 and FAX2) and one ER-localized FA transporter (ABCA2) in Chlamydomonas. Under standard growth conditions, FAX1/FAX2/ABCA2 over-expression lines (OE) accumulated up to twofold more TAG than the parental strain UVM4, and the total amounts of major polyunsaturated FAs (PUFA) in TAG increased by 4.7-fold. In parallel, the total FA contents and major membrane lipids in FAX1/FAX2/ABCA2-OE also significantly increased compared with those in the control lines. Additionally, the total accumulation contribution ratio of PUFA, to total FA and TAG synthesis in FAX1/FAX2/ABCA2-OE, was 54% and 40% higher than that in UVM4, respectively. Consistently, the expression levels of genes directly involved in TAG synthesis, such as type-II diacylglycerol acyltransferases (DGTT1, DGTT3 and DGTT5), and phospholipid:diacylglycerol acyltransferase 1 (PDAT1), significantly increased, and the expression of PGD1 (MGDG-specific lipase) was upregulated in FAX1/FAX2/ABCA2-OE compared to UVM4.

Conclusion: These results indicate that the increased expression of FAX1/FAX2/ABCA2 has an additive effect on enhancing TAG, total FA and membrane lipid accumulation and accelerates the PUFA remobilization from membrane lipids to TAG by fine-tuning the key genes involved in lipid metabolism under standard growth conditions. Overall, FAX1/FAX2/ABCA2-OE shows better traits for lipid accumulation than the parental line and previously reported individual FA transporter-OE. Our study provides a potential useful strategy to increase the production of FA-derived energy-rich and value-added compounds in microalgae.

Keywords: ABC transporter; Chlamydomonas reinhardtii; Fatty acid exporters; Genetic engineering; Polyunsaturated fatty acids; Triacylglycerol.

Abstract

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