Construction of a system for the stable expression of foreign genes in Dunaliella salina

A stable transformation system for the expression of foreign genes in the unicellular green marine alga (Dunalielia salina Teod.) was established. Using electroporation, the alga was transformed with a plasmid containing the hepatitis B surface antigen (HBsAg) gene and the chloramphenicol acetyltransferase (CAT) gene as a selectable gene. PCR and Southern blotting analysis indicated that the HBsAg gene was integrated into the D. salina genome. Northern dotting analysis showed that the HBsAg gene was expressed at the mRNA level. The stable expression of HBsAg protein in transformants was confirmed by HBsAg enzyme-linked immunosorbent assay (HBsAg ELISA) and Western blotting analysis. Also, PCR and Southern blotting analyses showed that the CAT gene was integrated into the D. salina genome, and CAT-ELISA indicated that CAT protein was stably expressed in the cells. The introduced HBsAg DNA and HBsAg protein expression were stably maintained for at least 60 generations in media devoid of chloramphenicol. This is the first report of the stable expression of foreign genes in D. salina.