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Green light for protoplast fusion
Fusion of protoplasts has been seen as a means of achieving hybridization between related species which, despite that relatedness, are not inter-fertile. In the past, much research effort has been invested in protoplast fusion as a route to crop improvement, and there has been some success with a limited number of genera, including Petunia and Citrus. Today, although GM has diverted attention from protoplast fusion, the latter still has potential applications. A major bottleneck in the process is the regeneration of plants from the fused protoplasts. Furthermore, even when apparently successful regeneration has been achieved, the resulting plants may be chimeric or may even have totally lost one of the parental genomes. Markers are needed to follow the fate of the two parental lines through fusion, culture and regeneration. Ideal markers will be those that can be readily and quickly detected by non-destructive techniques. One such potential marker is Green Fluorescent Protein (GFP), encoded by a gene isolated from the jellyfish, Aequorea victoria. Essential for its use as a marker in protoplast fusion is its ease of detection by illuminating live cells or tissues at the appropriate excitation wavelength. A group working at the Agricultural Research Institute in Valencia (Olivares-Fuster et al.; pp. 491-497) has fused transgenic protoplasts of citrange (a Citrus-Poncirus hybrid), expressing the GFP gene, with protoplasts of Citrus reticulata. GFP was monitored from initial fusion through to establishment of plants. Expression of the GFP gene was of course indicative of only one parental line; the presence of both was confirmed by the use of DNA markers. However, it is noted that different forms of GFP are available that fluoresce at different wavelengths; it would thus be possible to use this very practicable technique to check the presence of both parental lines and so monitor the success of the somatic hybridization.Professor J. A. Bryant
University of Exeter, UK
J.a.bryant{at}exeter.ac.uk
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