Shortened forms of beet necrotic yellow vein virus RNA-3 and -4: internal deletions and a subgenomic RNA

Abstract

Beet necrotic yellow vein virus RNA-3 and RNA-4, produced as full-length biologically active transcripts in vitro, can undergo spontaneous internal deletions when inoculated onto Chenopodium quinoa leaves along with RNA-1 and -2. The deletion process is specific, giving rise to only a few major species, and can be rapid; deleted forms appear after only one or two passages in leaves. In one of the shortened forms of RNA-4, the deletion precisely eliminated one copy of a 15 nucleotide (nt) direct sequence repeat from the fulllength prototype sequence, suggesting that 'copychoice' switching of the replicase-template complex from one repeat to the other during RNA replication was responsible for the generation of this deletion. The deletion found in a major shortened form of RNA-3, on the other hand, did not occur near sequence repeats but began with GU and ended with AG like a nuclear intron sequence. Thus it is possible that the deleted sequence has been removed by splicing. However, two other deletions that were characterized were not associated with either of these types of sequence feature. An approximately 600 nt 5'-terminally truncated nonencapsidated form of RNA-3 was also detected in infected plant tissue. The evidence suggests that it is a subgenomic RNA derived from RNA-3.

Vascular movement of beet necrotic yellow vein virus in Beta macrocarpa is probably dependent on an RNA 3 sequence domain rather than a gene product.

“…Internal deletions of RNA 3 which translationally activate ORF N can occur spontaneously during multiple steps of virus propagation in planta (Koenig et al, 1986 ;Bouzoubaa et al, 1991) but such deleted forms were not detected in B. macrocarpa (Fig. 4).…”

“…The 5h terminus of RNA 3sub maps to nucleotide 1230 (Bouzoubaa et al, 1991) (Fig. 1) and the 5h-proximal reading frame on RNA 3sub is ORF S (nucleotides 1274-1393), corresponding to a putative protein of 4n6 kDa (Fig.…”

“…The other ORF tested for a possible role in vascular movement lies downstream of ORF N. RNA 3 produces a subgenomic RNA, RNA 3sub, during infection (Bouzoubaa et al, 1991). The 5h terminus of RNA 3sub maps to nucleotide 1230 (Bouzoubaa et al, 1991) (Fig.…”

P0 proteins of European beet-infecting poleroviruses display variable RNA silencing suppression activity

“…BNYVV RNA1, -2, -3 and -4 are necessary for the natural infection and transmission processes for sugar beet (Koenig et al, 1986;Bouzoubaa et al, 1991). However, when BNYVV is mechanically inoculated into experimental hosts such as C. quinoa, RNA1 and -2 are sufficient to induce and maintain infection (Quillet et al, 1989).…”

3'-Terminal sequence of the plum pox virus PS and o6 isolates: evidence for RNA recombination within the potyvirus group

“…RNA recombination was observed in poliovirus 3 decades ago (Hirst, 1962), and since then has been demonstrated in other animal viruses [aphthovirus (King et al, 1982), coronavirus (Lai et al, 1985), alphavirus (Monroe & Schlesinger, 1983)] and diverse plant viruses. Such natural rearrangements have been demonstrated in tobamovirus (Shirako & Brakke, 1984), bromovirus (Bujarski & Kaesberg, 1986), tobravirus (Robinson et al, 1987), tombusvirus (Hillman et al, 1987), carmovirus (Li et al, 1989), alfalfa mosaic virus (Van der Kuyl et al, 1991), furovirus (Bouzoubaa et al, 1991), nepovirus (Rott et al, 1991) and hordeivirus (Edwards et al, 1992), some of them including the generation of defective interfering (DI) RNAs and recombination with and between satellite RNAs.…”