Construction of a transformation system for the stable expression of foreign genes in Chlorella sp.

A stable transformation system for the expression of foreign genes in the unicellular green marine alga ( Chlorella sp. MACC/C95)was established. Using electroporation, the alga was transformed with a plasmid containing the phytase gene under the control of CaMV35S promoter and the neomycin phosphotransferase (npt) as a selectable marker gene. The integration of the phytase gene into the Chlorella genome was revealed by PCR and Southern blotting analysis. RT-PCR analysis revealed the expression of phytase gene at the transcript level. The enhanced activity of phytase enzyme in the transformants confirmed the integration and successful expression of phytase gene. The introduced phytase gene and its protein expression were stably maintained for at least 30 generations in media devoid of selectable antibiotics G418. This is an important step toward the production of useful foreign proteins in Chlorella sp. MACC/C95.