A synthetic gene coding for the green fluorescent protein (GFP) is a versatile reporter in Chlamydomonas reinhardtii

The use of Chlamydomonas reinhardtii as a model system has been hindered by difficulties encountered in expressing foreign genes. We have synthesised a gene encoding green fluorescent protein (GFP) adapted to the codon usage of C. reinhardtii (cgfp). After verifying the gene was functional in Escher ichia coil, the cgfp was fused in frame to the phleomycin resistance gene b le from Streptoalloteichus hindustanus and expressed in C. reinhardtii unde r control of the rbcS2 promoter and intron sequences. The GFP-fluorescence was seen only in the nucleus demonstrating the nuclear accumulation of the Ble-GFP fusion protein. The cgfp was also fused to the chlamyopsin gene, co p, and expressed in C. reinhardtii under control of the cop promoter. The e yespot became fluorescent indicating that the opsin-GFP fusion protein was correctly directed into the eyespot along with the endogenous unmodified op sin. We conclude that cgfp provides a useful tool to visualize protein synt hesis and localisation in vivo in C. reinhardtii and possibly in related gr een algal species.