Heterologous Gene Expression System Using the Cold-Inducible Promoter in .

To increase the availability of microalgae as producers of valuable compounds, it is necessary to develop novel systems for gene expression regulation. Among the diverse expression systems available in microalgae, none are designed to induce expression by low temperature. In this study, we explored a cold-inducible system using the antifreeze protein (AFP) promoter from a polar diatom, . A vector containing the promoter () was generated to regulate nuclear gene expression, and reporter genes ( luciferase () and mVenus fluorescent protein ()) were successfully expressed in the model microalga, . In particular, under the control of , the expression of these genes was increased at low temperature, unlike , a promoter that is widely used for gene expression in . Promoter truncation assays showed that cold inducibility was still present even when was shortened to 600 bp, indicating the presence of a low-temperature response element between -600 and -477 bp. Our results show the availability of new heterologous gene expression systems with cold-inducible promoters and the possibility to find novel low-temperature response factors in microalgae. Through further improvement, this cold-inducible promoter could be used to develop more efficient expression tools.