The first virusoid was discovered in Nicotiana velutina plants infected with Velvet tobacco mottle virus R2 (VTMOV).

Circular RNAs impose constraints on RNA folding by which secondary structures that are favored for replication differ from those assumed during ribozyme-mediated self-cleavage.

This contrasts with satRNA of TBSV or the defective-interfering RNAs,[12] in which only a small portion of their respective sequences / secondary structures were found to be sufficient for replication.

[1] It was proposed that the hammerhead ribozyme structure of satLTSV is formed only transiently, similar to that observed by Song & Miller (2004) with satRPV (Cereal yellow dwarf polerovirus serotype RPV) RNA.

These structures are similar to those reported for CarSV and newt ribozymes,[16][17] which implies an ancient relationship between these divergent RNAs.

The observation by Collins et al., 1998 that the dimer of the satRYMV RNA is more efficiently self-cleaved than the monomer is consistent with the double hammerhead mode of cleavage.

[18] Considering properties such as their diminutive size, circular structure and the presence of hammerhead ribozymes, viroids may have had an ancient evolutionary origin distinct from that of the viruses.

Alternatively, the siRNAs and microRNAs generated during viral infections may have been amplified by helper virus replicases, whereby these molecules assembled to form satellite RNAs.

A phylogeny based on a manually-adjusted alignment in 2001 suggests that virusoids may form a clade of their own as a sister group to Avsunviroidae, which also possess hammerhead ribozymes.

[29][30] This group suggested that the scRYMV be designated as a virusoid satelliteRNA that could serve as a model system for both translation and replication.

The unique example of a foreign expression vector is Bamboo mosaic virus satellite RNA (satBaMV),[31] which possesses an open reading frame that encodes a 20-kDa P20 protein.