Stable Transformation of the Intact Cells of Chlorella Kessleri with High Velocity Microprojectiles

A transgenic expression system of Chlorella kessleri using the gene for ?-glucuronidase (GUS) was developed. Cells of this unicellular green alga were bombarded with the plasmid pBI 121, which bears (beta)-glucuronidase under the control of CaMV 35S promoter and the kanamycin resistant gene. Maximum GUS activity was obtained after 48 h of bombardment using a helium pressure of 900 kPa; GUS activity was then assayed for many generations. The stable transformants were able to grow on kanamycin containing medium after repeated passages between selective and nonselective medium and exhibited GUS activity comparable to that of control cells. Stable transformed cells were confirmed by polymerase chain reaction (PCR) and Southern hybridization of GUS probe with the genomic DNA of C. kessleri.