Direct Gene Transfer to Protoplasts

The first transgenic tall fescue plants were obtained by direct gene transfer to protoplasts (Wang et al., 1992). A protoplast is a cell from which the cell wall has been removed. Protoplast transformation is based on the direct uptake of plasmid DNA into protoplasts from the surrounding solutions (Potrykus, 1990; Saul and Potrykus, 1990). In contrast to dicot species, mesophyll-derived protoplasts from monocot species rarely undergo sustained mitotic division. Embryogenic cell cultures are thus the only source of totipotent protoplasts (protoplasts that have the potential to regenerate into whole plants) in grasses (Potrykus, 1990). This complicates the development of protoplast transformation systems because the establishment of embryogenic suspension cultures is time-consuming and requires experience. Although transgenic tall fescue plants were obtained by direct gene transfer to protoplasts in several laboratories in the 1990s (Dalton et al., 1995; Ha et al., 1992; Kuai et al., 1999; Wang et al., 1992), the transformation system has been replaced by more simple biolistic and Agrobacterium-mediated transformation methods.

 

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