The Mechanism of Entry of Viruses into Plant Protoplasts

Plant protoplasts may be efficiently infected with viruses. Attachment to the plasmalemma is a critical step in infection; positively charged viruses readily adhere and infect but negatively charged viruses require the presence of a polycation (e.g. poly-L-ornithine) before infection can occur. The role of the polycation appears to be twofold: to modify the charge of the virus and to damage the surface of the protoplast. Virus probably enters the protoplast during repair of damaged regions of the plasmalemma. Pinocytosis does not appear to play a significant part in inoculation.