Overexpression of the Transcription Factor AtLEC1 Significantly Improved the Lipid Content of Chlorella ellipsoidea

Xiao Liu; Dan Zhang; Jianhui Zhang; Yuhong Chen; Xiuli Liu; Chengming Fan; Richard R-C Wang; Yongyue Hou; Zanmin Hu

doi:10.3389/fbioe.2021.626162

Overexpression of the Transcription Factor AtLEC1 Significantly Improved the Lipid Content of Chlorella ellipsoidea

Front Bioeng Biotechnol. 2021 Feb 17:9:626162. doi: 10.3389/fbioe.2021.626162. eCollection 2021.

Authors

Xiao Liu¹, Dan Zhang^{1

2}, Jianhui Zhang¹, Yuhong Chen¹, Xiuli Liu³, Chengming Fan¹, Richard R-C Wang⁴, Yongyue Hou³, Zanmin Hu^{1

5}

Affiliations

¹ State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, China.
² Analysis and Test Center, Guangzhou Higher Education Mega Center, Guangdong University of Technology, Guangzhou, China.
³ Inner Mongolia Academy of Agriculture and Animal Husbandry, Huhhot, China.
⁴ United States Department of Agriculture, Agricultural Research Service, Forage and Range Research Laboratory, Utah State University, Logan, UT, United States.
⁵ College of Agriculture, University of Chinese Academy of Sciences, Beijing, China.

Abstract

Microalgae are considered to be a highly promising source for the production of biodiesel. However, the regulatory mechanism governing lipid biosynthesis has not been fully elucidated to date, and the improvement of lipid accumulation in microalgae is essential for the effective production of biodiesel. In this study, LEAFY COTYLEDON1 (LEC1) from Arabidopsis thaliana, a transcription factor (TF) that affects lipid content, was transferred into Chlorella ellipsoidea. Compared with wild-type (WT) strains, the total fatty acid content and total lipid content of AtLEC1 transgenic strains were significantly increased by 24.20-32.65 and 22.14-29.91%, respectively, under mixotrophic culture conditions and increased by 24.4-28.87 and 21.69-30.45%, respectively, under autotrophic conditions, while the protein content of the transgenic strains was significantly decreased by 18.23-21.44 and 12.28-18.66%, respectively, under mixotrophic and autotrophic conditions. Fortunately, the lipid and protein content variation did not affect the growth rate and biomass of transgenic strains under the two culture conditions. According to the transcriptomic data, the expression of 924 genes was significantly changed in the transgenic strain (LEC1-1). Of the 924 genes, 360 were upregulated, and 564 were downregulated. Based on qRT-PCR results, the expression profiles of key genes in the lipid synthesis pathway, such as ACCase, GPDH, PDAT1, and DGAT1, were significantly changed. By comparing the differentially expressed genes (DEGs) regulated by AtLEC1 in C. ellipsoidea and Arabidopsis, we observed that approximately 59% (95/160) of the genes related to lipid metabolism were upregulated in AtLEC1 transgenic Chlorella. Our research provides a means of increasing lipid content by introducing exogenous TF and presents a possible mechanism of AtLEC1 regulation of lipid accumulation in C. ellipsoidea.

Keywords: AtLEC1; Chlorella ellipsoidea; lipid content; regulation; transcriptome.