INFECTIOUS IN-VITRO TRANSCRIPTS FROM CLONED CDNA OF BEET NECROTIC YELLOW VEIN VIRUS RNA3 AND RNA4 AND THEIR FUNCTIONAL-STUDY

The full-length double-stranded cDNAs of beet necrotic yellow vein vir us RNA3 and RNA 4were synthesized by using oligo(dT) 15 as well as RNA 3 and RNA4 specific primers, and cloned downstream of the bacteriophag e Sp6 RNA polymerase promoter of the transcription vector pGEM3Zf(+). The in vitro ''run-off'' transcription products obtained in the presen ce of Sp6 RNA polymerase and template DNA have high biological activit ies. In the 2 transcription systems, the transcription and capping in 2 separate reactions are more efficient. The simultaneous transcriptio n and capping are not so efficient, but the transcripts are more infec tious. Although there are a number of nonviral nucleotide sequences at the 5'- and 3'-ends of RNA3 and RNA4 transcripts, the biological acti vities of both transcripts were not affected. The mechanical coinocula tion of sugarbeet roots with the infectious transcripts of the prepare d RNA3 and RNA4 and BNYVV Rg1 isolate has confirmed that RNA3 is the m ain cause of sugarbeet rhizomania.