JELLYFISH GREEN FLUORESCENT PROTEIN AS A REPORTER FOR VIRUS-INFECTIONS

The gene encoding green fluorescent protein (GFP) of Aequorea victoria was introduced into the expression cassette of a virus vector based o n potato virus X (PVX). Host plants of PVX inoculated with PVX.GFP bec ame systemically infected. Production of GFP in these plants was detec ted initially between 1 and 2 days postinoculation by the presence of regions on the inoculated leaf that fluoresced bright green under UV l ight. Subsequently, this green fluorescence was evident in systemicall y infected tissue. The fluorescence could be detected by several metho ds. The simplest of these was by looking at the UV-illuminated plants in a darkened room. The PVX.GFP-infected tissue has been analysed eith er by epifluorescence or confocal laser scanning microscopy. These mic roscopical methods allow the presence of the virus to be localized to individual infected cells. It was also possible to detect the green fl uorescence by spectroscopy or by electrophoresis of extracts from infe cted plants. To illustrate the potential application of this reporter gene in virological studies a derivative of PVX.GFP was constructed in which the coat protein gene of PVX was replaced by GFP. Confocal lase r scanning microscopy of the inoculated tissue showed that the virus w as restricted to the inoculated cells thereby confirming earlier specu lation that the PVX coat protein is essential for cell-to-cell movemen t. It is likely that GFP will be useful as a reporter gene in transgen ic plants as well as in virus-infected tissue.