The Transformation of the Unicellular Alga Chlamydomonas reinhardtii by Electroporation

The cell wall–lacking mutant CW-15 of the unicellular green alga Chlamydomonas reinhardtii was transformed by electroporation using plasmid pCTVHyg, which was constructed with the hygromycin phosphotransferase genehpt as the selective marker and the Tn5 transposon of Escherichia coli under the control of the virus SV40 early gene promoter. Under optimal conditions (106 mid-exponential cells/ml; electric field strength 1 kV/cm; and pulse length 2 ms), the transformation yielded 103 HygR transformants per 106 recipient cells. The exogenous DNA integrated into the nuclear genome of Ch. reinhardtii was persistently inherited through more than 350 cell generations. The advantages of this system for the transformation ofCh. reinhardtii with heterologous genes are discussed.