Infectious in vivo transcripts of plum pox potyvirus fulllength cDNA clone containing the cauliflower mosaic virus 35S RNA promoter

A full-length cDNA clone of an aphid non-transmissi-ble isolate of plum pox potyvirus (PPV) was rendered biologically active when placed under the control of the cauliflower mosaic virus 35S RNA promoter and the nopaline synthase polyadenylation signal. The cDNA was constructed so that the exact 5 ' end of the PPV RNA was present at the transcription initiation site. Inoculation of plasmid DNA onto Nicotiana bentha-miana led to systemic infection, whereas local lesions were produced in Chenopodium amaranticolor and C. quinoa, typical of an infection with PPV. Examination of infected plants revealed PPV-specific virus particles as well as viral RNA, the coat protein and the non-structural large nuclear inclusion protein (NIb). Potyviruses belong to the largest group of plant viruses and cause serious diseases in a number of economically important crop plants. Members of the potyvirus group are flexuous rods 720 to 900 nm in length (Hollings & Brunt, 1981) and encapsidate a single positive-sense RNA molecule of about 10 kb, attached to a 5'-linked protein (VPg) and including a poly(A) tract at the 3 ' end. The RNA is translated into a large polyprotein which is subsequently processed by at least two virus-encoded proteases. Upon proteolytic leavage this polyprotein yields the viral coat protein (CP) and the non-structural proteins helper component-protease, cylindrical inclu-sion protein and two nuclear inclusion proteins (NIa and NIb). In addition, at least wo other gene products which have not yet been identified are predicted from the nucleotide sequence of all potyviruses sequenced (Alliso