Transformed cells proliferate, giving rise to brightly fluorescent calli.
While we were able to generate 35S-mgfp4 transformed cells that were intensely fluorescent, and easily detectable by eye under long wavelength UV illumination, it proved difficult to regenerate fertile plants from the brightest transformants. It is possible that very high levels of GFP expression are mildly toxic or interfere with regeneration, perhaps due to the fluorescent or catalytic properties of the protein. In jellyfish photocytes, where high levels of GFP are well tolerated, the protein is found sequestered in cytoplasmic granules. In contrast, the mature protein is found throughout the cytoplasm and accumulates within the nucleoplasm of transformed Arabidopsis cells. If GFP is a source of fluorescence-related free radicals, for example, it might be advisable to target the protein to a more localised compartment within the plant cell.