EARLY EVENTS IN VIRUS PLANT INTERACTIONS

1. Plant viruses can only enter their host through a wounded plant cel l. Once in the cytoplasm, the virion must be disassembled, and for cer tain viruses with a ''+'' RNA genome, cotranslational disassembly of v irus particles has been described. 2. Subsequent to viral protein synt hesis which requires the host translational machinery, the ''+'' RNA g enome is replicated in the cytoplasm. Viral genome amplification requi res at least one viral-coded non-structural protein in conjunction wit h one or more host factors. 3. Early events in virus infection can be studied in systems that hinder these events. This is the case of natur al hosts that are resistant to viruses: mutant viruses which overcome such resistance have been described. It is also the case of geneticall y engineered plants that are protected from virus infection. Both type s of systems should help in determining the mode of interaction involv ed, and possibly also the host factor(s) involved in the various steps of virus infection.