IMAGING THE GREEN FLUORESCENT PROTEIN IN PLANTS - VIRUSES CARRY THE TORCH

The green fluorescent protein (GFP) was introduced into plant cells us ing potato virus X as a vector. The GFP was produced at high levels wi thin virus-infected cells by utilising a duplication of the viral coat protein subgenomic RNA promoter sequence to direct transcription of m RNA encoding the GFP. We also exploited the ability of GFP to retain i ts fluorescence when fused to other proteins by fusing it to the PVX c oat protein. The resultant fluorescent virus became systemic and its m ovement from cell to cell was traced using confocal laser scanning mic roscopy. Using PVX as the vector, additional fusions of the GFP were m ade to the movement protein of tobacco mosaic virus (TMV). The fluores cent fusion protein produced was targeted to specific wall sites thoug ht to be plasmodesmatal pit fields. The utility of virus-based vectors for the delivery and targeting of GFP in living plant cells is discus sed.