Recombination between satellite RNAs of turnip crinkle virus.

Abstract

Turnip crinkle virus (TCV) is associated with satellite (sat) RNAs (sat‐RNA D, sat‐RNA F), defective interfering (DI) RNAs (DI RNA G, DI1 RNA), and one RNA with properties of both sat‐RNAs and DI RNAs (sat‐RNA C). When plants were inoculated with TCV, sat‐RNA D and in vitro sat‐RNA C transcripts containing non‐viable mutations in the 5′ domain, recombinant sat‐RNAs were recovered. These recombinants were composed of sat‐RNA D at the 5′ end and sat‐RNA C sequences at the 3′ end. Analysis of 20 independent recombination junctions revealed that unequal crossing‐over had occurred in planta in a region of sequence similarity between the two sat‐RNAs which resulted in the duplication of 3‐16 nucleotides. Thirty percent of the sat‐RNA recombinants also had one to three additional nucleotides inserted at the crossover junctions which did not correspond to either sat‐RNA C or sat‐RNA D sequence. The right side of the recombination junctions always began with one of three consecutive nucleotides of sat‐RNA C. Based on the similarity between this sequence of sat‐RNA C, the right side junction of DI RNA G and the 5′ end of TCV, as well as the sequence similarity between right side junctions of DI1 RNA and sat‐RNA C and the 5′ end of the sat‐RNAs, a replicase‐driven copy choice mechanism is proposed.(ABSTRACT TRUNCATED AT 250 WORDS)

De novo generation of cymbidium ringspot virus defective interfering RNA

“…As pointed out by Cascone et al (1990), the same mechanism may be operating in RNA recombination and generation of DI RNA. In the 'copy choice' mechanism (Lazzarini et al, 1981) the RNA polymerase may stop before reaching the 5' end of the template RNA and jump, together with nascent complementary RNA, to another site on a different or the same template.…”

“…A model based on discontinuous action of the RNA polymerase has been proposed to explain the generation of DI RNA from the mouse hepatitis coronavirus genome (Makino et al, 1988). Likewise, dissociation of RNA polymerase from the template due to the presence of a hairpin structure is at the base of the model presented by Cascone et al (1990) for the generation of TCV DI RNA and RNA recombinants.…”

Formation of multimers of cucumber mosaic virus satellite RNA.

“…Although multimeric forms of satellite RNA of CMV, peanut stunt cucumovirus (PSV), turnip crinkle carmovirus (TCV) and cymbidium ringspot tombusvirus (CyRSV) have been detected, the mechanisms of replication of these satellites are unclear . Recently, Carpenter et al (1991) proposed that multimers of TCV linear subviral RNAs are not formed by a rolling circle mechanism, but are generated by a replicasedriven copy-choice mechanism (Cascone et al, 1990). In the case of CyRSV, concatemeric forms of satellite RNAs were Author for correspondence : Tomohide Natsuaki.…”

RNA Recombination of Hepatitis Delta Virus in Natural Mixed-Genotype Infection and Transfected Cultured Cells

“…Genetic recombination is an important process for eliminating detrimental mutations and ensuring greater genetic diversity. Recombination occurs in mixed infections of some closely related RNA viruses that encode their own RNA polymerases (30) and in viroids that are dependent on the cellular enzymatic activities for replication (1,4,14,23,24,43,47,52,54). However, although phylogenetic analysis suggests that genetic recombination can occur both between and within HDV genotypes (67), HDV recombinants have never been isolated from HDV mixed-genotype infections (66) either in nature or in the laboratory.…”