Viral RNA synthesis by a particulate fraction from cucumber seedlings infected with cucumber mosaic virus.
Particulate preparations from cucumber mosaic virus (CMV)-infected cucumber cotyledons incorporated [alpha-32P]GTP into products which, after phenol extraction, appeared to be double-stranded forms of the four CMV RNAs. In preparations isolated 3 to 5 days after inoculation, the label was incorporated mostly into plus RNA as shown by dot-blot hybridization using single-strand recombinant DNA clones of CMV RNA. After a short pulse the labeled material consisted mostly of small heterogeneous products, but part of the label could be chased into full-length RNAs, demonstrating that the synthetic process was continuous strand elongation rather than terminal addition. CMV RNAs added to the particulate fraction did not give rise to high molecular weight transcripts. In addition to the high molecular weight defined products which remained in the particulate fraction, small heterogeneous products, complementary to plant RNA and to viral RNA of both plus and minus polarity, were released into the incubation medium. They appeared to be products of the virus-induced Mr 100,000 (100K) protein which is solubilized from the particulate fraction during incubation. However, when the particulate fraction was first subjected to an extensive solubilization and washing treatment in order to remove the M(r) 100K protein [D. S. Gill, R. Kumarasamy, and R. H. Symons (1981) Virology 113, 1-8], and then used for product synthesis, a large amount of the product was still of small size, suggesting that the synthesis of high and low molecular weight RNA was intrinsically connected, and that the M(r) 100K protein was not merely contaminating the particulate fraction.
Jaspars
E M
EM
Adelaide University Centre for Gene Technology, Department of Biochemistry, University of Adelaide, Adelaide, South Australia 5000, Australia.
Gill
D S
DS
Symons
R H
RH