Satellite Nature of the Viroid-like RNA-2 of Solanum Nodiflorum Mottle Virus and the Ability of Other Plant Viruses to Support the Replication of Viroid-like RNA Molecules

Abstract

SUMMARYThe stock culture of solanum nodiflorum mottle virus (SNMV) was freed from RNA-2 by passage through single lesions induced in inoculated leaves of Nicotiana debneyi by dilute inocula of partially purified SNMV RNA-1. This isolate (S1) was indistinguishable serologically and in symptomatology from the stock culture of SNMV. Using a sensitive bioassay for detecting RNA-2, no SNMV RNA-2 was found in RNA from particles of the S1 isolate purified after three successive passages in Nicotiana clevelandii. Addition of SNMV RNA-2 (which is not infective alone) had little or no effect on the infectivity of S1 RNA but restored the RNA content of particles to that found in the stock culture (RNA-1 and RNA-2). However, S1 did not support the replication of the RNA-2 from lucerne transient streak virus (LTSV). The possible interaction of the RNA-2 species from LTSV and SNMV with the genomes of other plant viruses was tested by mixing the RNA-2 species with nucleic acid from 11 other viruses. The survival of RNA-2 activity on inoculated leaves for up to 15 days complicated the interpretation of the results of these tests but a small amount of LTSV RNA-2 and SNMV RNA-2 was obtained only from particles of turnip rosette virus purified from plants inoculated with the relevant RNA mixtures. These and other data suggest that these RNA-2 molecules with physicochemical properties similar to viroids found in particles of some sobemoviruses are satellite RNA species whose multiplication is assisted by some, but not all, of the viruses in this group.

Replication and encapsidation of the viroid-like satellite RNA of lucerne transient streak virus are supported in divergent hosts by cocksfoot mottle virus and turnip rosette virus

“…These results were equivocal, however, because the necrotic lesions were few in number and/or difficult to detect, and symptoms were occasionally erratic. The work presented here provides evidence, via nucleic acid hybridization, that both TRosV and CfMV support the replication and packaging of LTSV RNA-2, confirming that this sat-RNA does not specifically require genomic LTSV RNA for replication (Paliwal, 1984b;Jones & Mayo, 1984). Other instances of nonspecificity in the interaction between helper sobemoviruses and sat-RNA have been reported.…”

“…In situ hybridization of viral RNA samples in dried 2 % agarose-formaldehyde gels showed that the high M r genomic RNAs from LTSV, CfMV and TRosV did not hybridize with the LTSV RNA-2 specific probe, suggesting that no sequence homology exists between these RNAs and LTSV sat-RNA (data not shown). Jones & Mayo (1984) observed that co-inoculation of TRosV and LTSV RNA-2 on Chenopodium quinoa resulted in an apparent change of lesion type, from chlorotic to necrotic, and this was considered to be due to LTSV RNA-2 replication in the presence of TRosV. A small proportion of the progeny virus from this mixed infection, following propagation in B. rapa, induced necrotic lesions on C. amaranticolor.…”

“…The RNA-2 of LTSV lacks helper specificity in that it replicates in association with SoMV (Francki et al, 1983b) and SBMV (Paliwal, 1984b). Moreover, preliminary data (Jones & Mayo, 1984) indicate that TRosV may support LTSV RNA-2 replication in Chenopodium amaranticolor. Previous studies (reviewed by Fritsch & Mayo, 1989) concerning propagation of viroid-like sat-RNAs by helper viruses had been limited to dicotyledonous hosts, and only recently (Miller et al, 1991) has a sat-RNA been shown to be associated with barley yellow dwarf luteovirus, a virus that affects monocotyledons.…”

“…LTSV) for replication (Tien-Po et aL, 1981;. Viroid-like sat-RNAs have also been reported in a few other sobemoviruses, namely velvet tobacco mottle virus (VTMoV; Randles et al, 1981;Francki et aL, 1986), Solanum nodiflorum mottle virus (SNMV; Jones & Mayo, 1984) and subterranean clover mottle virus (SCMoV; Francki et al, 1983a). Most sobemoviruses including cocksfoot mottle virus (CfMV), turnip rosette virus (TRosV), southern bean mosaic virus (SBMV) and sowbane mosaic virus (SoMV), however, are normally devoid of sat-RNAs (reviewed by Hull, 1988).…”

Cucumovirus Satellite RNAs Cannot Replicate Autonomously in Cowpea Protoplasts

“…The possibility that some viral satellites utilize host-encoded enzyme(s) for their replication was recently suggested by us (Linthorst & Kaper,t984a), and by Jones & Mayo (1984), along with the suggestion that if so, then the satellites' dependence upon their helper viruses would have to be attributed to some function relating to the intercellular movement and systemic spread of the helper throughout the plant. One approach towards resolving this question would be to see whether certain viral satellites are capable of independent multiplication in protoplasts, which does not necessitate spread from cell to cell.…”