The helper virus mediating replication of the satellite RNA (RNA 3) of pea enation mosaic virus (PEMV) consists of two autonomously replicating, taxonomically unrelated viral RNAs with ties to the luteovirus (RNA 1) and the newly proposed umbravirus (RNA 2) genera. The following study dissects the relative contribution of each of the genomic RNAs of PEMV to the subsistence and dissemination of this satellite RNA. Infectivity assays in a pea protoplast system demonstrate that RNA 2 alone is responsible for the replication of RNA 3, an observation that is supported in part by shared regions of sequence homology at the 5′ and 3′ termini of both RNAs. In pea seedlings, infectivity assays also demonstrated that the presence of RNA 2 alone is necessary for the systemic invasion of RNA 3. In contrast, the luteovirus-like phase of PEMV (RNA 1) is solely responsible for the encapsidation and aphid transmission of both RNA 2 and the satellite RNA. In a manner comparable to several other virus-satellite systems, the satellite of PEMV also displays a differential response in its capacity to attenuate symptom expression in selected host species. Thus, the satellite RNA of PEMV exists in a trilateral arrangement with its host and two viral RNAs, comparable in many respects to the satellite-virus-host interaction occurring with groundnut rosette disease.
AllisonR. F.,
JandaM.,
AhlquistP.1988; Infectious in vitro transcripts from cowpea chlorotic mottle virus cDNA clones and exchange of individual RNA components with brome mosaic virus. Journal of Virology 62:3581–3588
DemlerS. A.,
De ZoetenG. A.1989; Characterization of a satellite RNA associated with pea enation mosaic virus. Journal of General Virology 70:1075–1084
DemlerS. A.,
De ZoetenG. A.1991; The nucleotide sequence and luteovirus-like nature of RNA 1 of an aphid non-transmissible strain of pea enation mosaic virus. Journal of General Virology 72:1819–1834
DemlerS. A.,
RuckerD. G.,
De ZoetenG. A.1993; The chimeric nature of the genome of pea enation mosaic virus: the independent replication of RNA 2. Journal of General Virology 74:1–14
DemlerS. A.,
BorkhseniousO. N.,
RuckerD. G.,
De ZoetenG. A.1994; Assessment of the autonomy of replicative and structural functions encoded by the luteo-phase of pea enation mosaic virus. Journal of General Virology 75:997–1007
MurantA. F.1990; Dependence of groundnut rosette virus on its satellite RNA as well as on groundnut rosette assistor luteovirus for transmission of Aphis craccivora
. Journal of General Virology 71:2163–2166
MurantA. F.1993; Complexes of transmission-dependent and helper viruses. In Diagnosis of Plant Virus Diseases pp 334–357MatthewsR. E. F.
Edited by Boca Raton: CRC Press;
ReismanD.,
De ZoetenG. A.1982; A covalently linked protein at the 5ʹ-ends of the genomic RNAs of pea enation mosaic virus. Journal of General Virology 62:187–190
TaborS.,
RichardsonC. C.1987; DNA sequence analysis with a modified bacteriophage T7 DNA polymerase. Proceedings of the National Academy of Sciences U.S.A.: 844767–4771