Stable expression of hepatitis B surface antigen gene in Dunaliella salina (Chlorophyta)

A stable transformation system for the expression of foreign genes in the unicellular marine green alga Dunaliella salina was established. Among five antibiotics, 60 μg mL^-1 chloramphenicol completely inhibited growth. Of five promoters tested, the ubiquitin-Ω promoter yielded the highest β-glucuronidase (GUS) activity. The hepatitis B surface antigen (HBsAg) gene was introduced into the cells by using electroporation. PCR and Southern blot analysis amd it was shown that the gene was integrated into the genome. The stable expression of HBsAg protein was confirmed by enzyme-linked immunosorbent assay (ELISA) and Western blot analysis. The introduced DNA and HBsAg expression were maintained stable for at least 60 generations in medium devoid of chloramphenicol. This is an important step toward the production of useful foreign proteins in the alga.