Expression of the SARS-CoV-2 nucleocapsid (N) gene in Chlorella vulgaris via electroporation-mediated transformation.

The microalga Chlorella vulgaris is a unicellular photosynthetic microorganism with the potential of serving as a host organism for foreign genes. Utilising C. vulgaris as a host organism to express the SARS-CoV-2 structural protein, such as the nucleocapsid (N) gene, is a sustainable approach with high scalability. Here, we genetically engineered C. vulgaris with the N gene of SARS-CoV-2. Initially, a recombinant plasmid, pCAMBIA1303 harbouring the SARS-CoV-2 N gene, was transformed into C. vulgaris via electroporation. Subsequently, the transgenic C. vulgaris was cultivated in BG11 medium containing hygromycin B as the selection marker. We then evaluated the success of the transformation through PCR, RT-PCR, and LC-MS/MS assays. The results showed that the N gene was successfully transformed and expressed in the transgenic C. vulgaris culture. Furthermore, six consecutive generations of the transgenic C. vulgaris demonstrate stable integration and transcriptional expression of the transgene. This study highlights the potential of C. vulgaris as a host organism for viral genes, i.e., SARS-CoV-2 N gene, and potentially lays the groundwork for future development of a microalgae-based edible vaccine using C. vulgaris against SARS-CoV-2.