Artificial miRNA Inhibition of PEPC Increases Fatty Acid Production in Chlamydomonas reinhardtii

Nutrient limitation, such as nitrogen depletion, is the most used method for improving microalgae fatty acid production. However, these harsh conditions also significantly inhibit algal growth. To avoid these problems, a team of researchers from Shenzhen University used artificial microRNA (amiRNA) technology to manipulate metabolic pathways and increase fatty acid contents effectively in Chlamydomonas reinhardtii.

Aiming to downregulate the expression of phosphoenolpyruvate carboxylase (PEPC), the team designed amiRNAs against two CrPEPC genes, which catalyzes the formation of oxaloacetate and regulates carbon flux, and transformed them into Chlamydomonas cells. These amiRNAs were then induced by heat shock treatment.

The transcription levels of amiRNAs increased 16–28 times, resulting in the remarkable decreases of the expression of CrPEPCs. This resulted in the inhibition of the expressions of the CrPEPC genes which significantly increased the total fatty acid content in the transgenic algae, thus, also increasing the content of C16–C22 fatty acids.

These results suggest that amiRNAs can effectively downregulate the expression of CrPEPCs in C. reinhardtii, resulting in an increased fatty acid synthesis.