Liposome-mediated infection of plant protoplasts with tobacco mosaic virus RNA.

Tobacco mosaic virus (TMV) RNA was encapsulated in large unilamellar vesicles (LUV) of phosphatidylserine and was introduced into protoplasts from Vinca rosea suspension cultures. Infection could be effected by brief incubation of protoplasts with the LUV containing TMV-RNA in the presence of either polyethylene glycol or polyvinyl alcohol. The presence of these polymers was essential for infection, and postinoculation washing with the high pH-high Ca2+ buffer enhanced infection significantly. Up to 80% of protoplasts could be infected under the optimal conditions as demonstrated by immunofluorescence technique. Calculations showed that around 2 x 10(6) TMV-RNA molecules were added per infected protoplast, indicating that the efficiency of infection by this method compares favorably with those by the existing methods for inoculating protoplasts from mesophyll cells with TMV-RNA. The significance of using protoplasts from cultured cells for infection with plant viruses and their nucleic acids is discussed.