High-level expression of a synthetic red-shifted GFP coding region incorporated into transgenic chloroplasts

We describe here a synthetic red-shifted variant of GFP that can be introdu ced into tobacco plastid genomes and is highly expressed in regenerated pla nts that appear normal and fertile. The variant contains the S65G and S72A mutations which shift the absorption maximum from the 395 nm of wild-type G FP closer to 488 nm, a wavelength emitted by a laser commonly used in confo cal microscopy. In addition to enhanced fluorescence, the removal of signif icant absorption below 450 nm will potentially facilitate double-labelling experiments. The variant GFP encoded by the synthetic gene can be expressed at a high level, forming approximately 5% of total leaf protein.