Infectious virus in transgenic plants inoculated with a nonviable, P1-proteinase defective mutant of a potyvirus.
A mutant (P1-616) of the tobacco vein mottling potyvirus that contains a four-codon insertion in the P1 protein coding region of the viral RNA is unable to infect the normal host plant of the virus. Processing of the P1/HC-Pro cleavage site does not occur during in vitro translation of the mutant viral RNA. When plants transformed with the P1/HC-Pro/P3 coding region of tobacco vein mottling potyvirus RNA were inoculated with P1-616, some of them became infected, although there was a delay in the production of disease symptoms. Virus isolated from these plants was able to infect nontransgenic plants. Two variants of the recovered, infectious virus contained single-nucleotide alterations in the four-codon insertion in the P1-616 genome. In vitro translation of the variant genomic RNAs resulted in partial processing of the P1/HC-Pro cleavage site, although serological analysis of infected tissue showed complete processing in vivo. These results indicate that limited complementation of P1-616 occurs in the transgenic plants and that eventually there arises one or more variants of the mutant sequence that can effect P1/HC-Pro processing and therefore be replicated.
D016254:Mutagenesis, Insertional; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D017800:Potyvirus / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D012367:RNA, Viral; D017423:Sequence Analysis, RNA; D014026:Nicotiana / Q000821:virology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*