the dark side of translational fusions

Inhibitory effects of protein function are usually associated with mutations within the coding region of a gene. Inhibition can also come from additions of elements to a protein. I was reading a paper recently that showed that the C-terminal addition of GREEN FLUORESCENT PROTEIN (GFP) to a gene construction actually affects the ability of the protein to perform, in vivo. In order for plants to flower, a small protein (~25 kDa), called FLOWERING LOCUS T (FT) must be transported out of the leaves, through the petiole, loaded into the phloem, up through the plants vasculature, where it eventually reaches the shoot apical meristem to induce flowering. The small nature of this protein, accompanied with the long distance it must travel to accomplish one of its jobs, can be negatively affected by the addition of GFP, used to detect sub-cellular localization.  The translational fusion of GFP to FT decreases the efficiency of FT to drive flowering in an ft mutant background. This is supported by flowering time assays in Arabidopsis.