Kinetics of accumulation of citrus tristeza virus RNAs.

摘要

Citrus tristeza closterovirus is a complex ssRNA virus. The 5' section of its genome is expressed as a c. 400 kDa polyprotein that is proteolytically processed. The 10 3' open reading frames are expressed from 3' coterminal subgenomic RNAs (sg RNAs). The kinetics of accumulation of genomic and sg RNAs and coat protein of isolate T36 of CTV were similar in protoplasts of the natural host, citrus, and the non host Nicotiana tabacum. Newly synthesized genomic RNA was detected 2 days post-inoculation and increased to a max. after 3-5 days. The RNA complementary to the full length virion RNA increased with similar kinetics, but at c. 1/10 the concn of genomic plus strands. Many of the abundant sg RNAs also accumulated in parallel to that of the genomicRNA. The smallest sg RNA, corresponding to the p23 gene, increased earlier, however. Different sg RNAs accumulated in greatly differing amounts. In general, the 3'-most sg RNAs accumulated to higher levels than 5' sg RNAs. However, the 3' sg RNAs p13 and p18 also accumulated to low levels. The 2 3'-most sg RNAs (p23 and p20) accumulated to high levels almost equal to that of the genomic RNA. The accumulation curve for coat protein paralleled that of its RNA. This suggested that its regulation was transcriptional. Progeny virions from protoplasts were used to sequentially infect new protoplasts. These served as a potential source of virus that could evolve free from genetic selection in intact plants for aphid transmission and movement.