Red clover RNA virus 1: functional analysis of ORF2 protein, associations with co-infecting viruses, and seed transmission.

A previously undescribed group of related plant viruses has recently been identified within the Benyviridae family. This group is called reclovirids, named after the type species, red clover RNA virus 1 (RCRV1). The single genomic RNA of most reclovirids contains two main open reading frames (ORFs): a large, well-conserved 5′-proximal ORF1 that encodes a viral replicase and a less conserved 5′-distal ORF2 that encodes a polypeptide of unknown function with a C4-type zinc finger motif. In this study, the ORF2 proteins of RCRV1 and a Gymnadenia rhellicani virus, another reclovirid, are found to be unable to serve as viral movement proteins (MPs) in a complementation assay and fail to suppress RNA silencing induced by double- and single-stranded RNA. Transcriptomic analysis of an RCRV1-infected plant revealed the presence of two other, previously unknown viruses of the Rhabdoviridae and Qinviridae families. Further analysis of publicly available sequencing data demonstrated that two independently studied RCRV1-infected plants both contained co-infecting viruses. In one case, RCRV1 was found together with a virus of genus Varicosavirus, family Rhabdoviridae, which has no MP gene, suggesting that, in the absence of its own MP and MP provided by the co-infecting virus, RCRV1 likely does not move cell to cell in infected plants. Additionally, RCRV1 is shown to be transmitted by seeds. Taken together, the presented data support the view that reclovirids are vertically transmitted persistent viruses.