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 introduced into tobacco plastid genomes and is highly expressed in regenerated plants 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 GFP closer to 488 nm, a wavelength emitted by a laser commonly used in confocal microscopy. In addition to enhanced fluorescence, the removal of significant 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.