Table_1_Overexpression of the Transcription Factor AtLEC1 Significantly Improved the Lipid Content of Chlorella ellipsoidea.XLSX

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.

微藻被认为是生产生物柴油的极具潜力的原料。然而，迄今调控脂质生物合成的分子机制尚未完全阐明，而提高微藻的脂质积累量对于高效生产生物柴油至关重要。本研究将拟南芥中影响脂质含量的转录因子（transcription factor，TF）LEAFY COTYLEDON1（LEC1）转化至椭圆小球藻中。与野生型（wild-type，WT）菌株相比，在混合营养培养条件下，转入AtLEC1的转基因菌株的总脂肪酸含量和总脂质含量分别显著提升24.20%~32.65%和22.14%~29.91%；在自养培养条件下则分别显著提升24.4%~28.87%和21.69%~30.45%。与此同时，两种培养条件下转基因菌株的蛋白质含量分别显著降低18.23%~21.44%和12.28%~18.66%。值得注意的是，脂质与蛋白质含量的变化并未影响两种培养条件下转基因菌株的生长速率与生物量。转录组数据分析显示，转基因菌株LEC1-1中有924个基因的表达量发生显著变化，其中360个基因上调表达，564个基因下调表达。基于实时定量聚合酶链反应（quantitative real-time polymerase chain reaction，qRT-PCR）结果，脂质合成通路关键基因如乙酰辅酶A羧化酶（ACCase）、甘油-3-磷酸脱氢酶（GPDH）、磷脂二酰甘油酰基转移酶1（PDAT1）和二酰甘油酰基转移酶1（DGAT1）的表达谱均发生显著改变。通过对比椭圆小球藻和拟南芥中受AtLEC1调控的差异表达基因（differentially expressed genes，DEGs），我们发现，在AtLEC1转基因椭圆小球藻中，约59%（95/160）的脂质代谢相关基因呈上调表达。本研究通过导入外源转录因子，为提高微藻脂质含量提供了可行途径，并揭示了AtLEC1调控椭圆小球藻脂质积累的潜在分子机制。