结合ASGARD的CRISPRa技术在索罗金小球藻FZU60中的应用

APPLICATION OF THE CRISPRA TECHNOLOGY WITH ASGARD IN CHLORELLA SOROKINIANA FZU60

  • 摘要: 为建立索罗金小球藻(Chlorella sorokiniana) FZU60的高效遗传转化体系用于分子调控机制研究并提高其高附加值代谢产物的产量, 研究建立了基于CRISPR/dCas9的转录激活系统(CRISPRa), 结合适应性单链向导RNA (sgRNA)辅助调控基因表达(ASGARD)技术, 对基因进行随机激活。抗性筛选结果显示, 600 μg/mL潮霉素B可以抑制藻细胞生长。将构建的连接有高鸟嘌呤含量sgRNA的质粒pLWR-dzCas9-VP64::sgHG进行电击转化, 在潮霉素B抗性平板上经过多轮筛选获得具有稳定抗性且生长较快的转化藻株, PCR和RT-qPCR验证结果显示质粒已经成功转入和表达。进一步分析发现, 异养条件下转化藻株的生物量浓度均高于野生型藻株, 且转化藻株的蛋白质、油脂和色素含量和产量显著提高。其中, 转化藻株V-6的蛋白质含量和产量分别达到了452.83 mg/g和2384.32 mg/L, 与野生型藻株相比分别增长了17.97%和32.82%; 油脂含量和产量高达169.38 mg/g和891.56 mg/L, 与野生型相比提高了23.20%和38.97%; 叶绿素含量与野生型相近, 产量与野生型相比提高了18.44%; 类胡萝卜素含量与野生型无显著性差异, 产量与野生型相比提高了13.57%。因此, 本研究获得的转化藻株具有优异的蛋白质、油脂和色素生产能力。研究结果为索罗金小球藻FZU60基因编辑技术的建立提供了技术支撑, 为提高其高附加值代谢产物的产量提供了重要的理论依据。

     

    Abstract: To establish an efficient genetic transformation system for investigating molecular regulatory mechanisms and to increase the yield of its high-value-added metabolites in Chlorella sorokiniana FZU60, a CRISPR/dCas9-based transcriptional activation system (CRISPRa) was developed and combined with Adaptive Single-guide Assistant Regulatory DNA (ASGARD) to enable random gene activation. Resistance screening indicated that 600 μg/mL hygromycin B effectively inhibited algal cell growth. The constructed plasmid pLWR-dzCas9-VP64::sgHG, which carries a sgRNA with high guanine content, was introduced into algal cells via electroporation. After multiple rounds of screening on hygromycin B-resistant plates, transformed algal strains with stable resistance and rapid growth were obtained. The PCR and RT-qPCR verification results showed that the plasmid had been successfully transferred and expressed. Further analysis revealed that all transformed algal strains achieved higher biomass concentration than the wild type strain under heterotrophic conditions. The content and production of protein, lipid, and pigment of the transformed algal strain were significantly increased. Among them, the protein content and production of the transformed algal strain V-6 reached 452.83 mg/g and 2384.32 mg/L, representing increases of 17.97% and 32.82% over the wild type strain, respectively; lipid content and production were as high as 169.38 mg/g and 891.56 mg/L, which were 23.20% and 38.97% higher than those of the wild type respectively. Chlorophyll content remained similar to that of the wild type, whereas chlorophyll production increased by 18.44%; carotenoid content showed no significant difference from the wild type, while carotenoid production rose by 13.57%. Therefore, the transformed algal strain obtained in this study exhibits excellent capabilities for producing protein, lipid, and pigment. These findings provide technical support for establishing gene-editing techniques in C. sorokiniana FZU60 and offer a crucial theoretical basis for enhancing the production of high-value metabolites from this alga.

     

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