Notes on Genus: Babuvirus


Type member: Banana bunchy top virus


General Description

The genus Babuvirus (from the type member Banana bunchy top virus) is one of two genera in the family Nanoviridae, which consists of viruses with small (18-19 nm) isometric virions and a multipartite (6 to 8 or more segments) ssDNA genome, each segment of which is circular and about 1kb in size. It currently contains the single virus with six segments and two unidirectionally transcribed ORFs on DNA1. Viruses of dicotyledonous plants that probably have 8 (or more) monocistronic segments, have been retained in the genus Nanovirus.


Virions isometric (icosahedral), not enveloped 18-19 nm in diameter.


Six closed circular single stranded DNA components, each about 1kb in size. Additional DNA segments associated with some isolates and encoding replication-associated proteins are now regarded as alphasatellites.

Genus Genomic Organization

Most segments are monocistronic. There is a putative stem loop structure in the non-coding region of each segment which has a conserved 9-nucleotide sequence at its apex.

Type Member Genomic Organization

The six DNA components and their encoded proteins are:
putative product
DNA-R (1)1111replication initiator protein M-Rep (34 kDa) and nested protein of about 5 kDa
DNA-U3 (2)1060Unknown protein U3 of about 10 kDa
DNA-S (3)1075coat protein (20 kDa)
DNA-M (4)1043movement protein (14 kDa)
DNA-C (5)1018cell-cycle link (Clink) protein (19 kDa)
DNA-N (6)1089nuclear shuttle protein NSP (17 kDa)