Notes on Genus: Begomovirus betasatellites
no particles of their own
Single stranded satellite DNAs have been found associated with several plant viruses, and these currently fall into two major groups. The Alphasatellites
encode an autonomously replicating Rep protein and are found in association with monopartite viruses in the genus Begomovirus
and multi-component viruses in the family family Nanoviridae
. In contrast, the Betasatellites
encode a symptom-inducing protein in the complementary (negative) sense and have only been found in association with monopartite viruses in the genus Begomovirus
There are no distinctive virions, because the satellite DNA is encapsidated by the helper virus.
Monopartite, circular, ssDNA of 1300-1400nt.
Genus Genomic Organization
The sequences were originally labelled DNA beta. Full length versions of these have about 1350nt and encode a single protein of 14-16 kDa (C1 protein) in the complementary (negative) sense that is responsible for symptom production. They are not officially classified by ICTV, but studies by geminivirologists (see Briddon et al., 2008. Archives of Virology 153:763-781) and our own subsequent analyses have been used to organise sequences into "species-like" clusters within which the sequences are closely related (usually >78% nt identity) to one another.
Type Member Genomic Organization
There is no formal type member.