ABSTRACT
The green fluorescent protein (GFP) has proved an outstanding tool for studying various biological questions and revolutionized functional cell biology. The jellyfish Aequorea victoria protein was introduced into cell biology and biotechnology shortly after the gfp gene was cloned (Prasher et al. 1992). It was shown that the gene could be expressed in other organisms and detected as green fluorescence following excitation with UV or blue light (Chalfie et al. 1994). Unlike GUS, expression and localization of GFP can be easily detected in living cells and without addition of cofactors, substrates, or other proteins (Sheen et al. 1995). The stability of the brightly fluorescing molecule allows visualizing molecular events in situ and in real time. Mutations of the gfp-gene have led subsequently to the design of a number of improved GFP varieties, which are not only brighter than the wild type, but also available in different colors, making multichannel detection possible [for review, see Chalfie and Kain (1998) and Tsien (1998)]. Multichannel detection was exploited, for example, in the field of microbial ecology, where differently marked bacteria strains could be followed simultaneously on plant roots (Bloemberg et al. 2000).
