Notes on Family: Nanoviridae



General Description

This family consists of viruses with small (18-19 nm) isometric virions and a multipartite (6-11 segments) ssDNA genome, each segment of which is circular and about 1kb in size. The small size of the genome segments and the stunting effects often caused in plants explain the name (from the Greek nanos = small).


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


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. Each member has up to 4 segments encoding replication proteins of about 33 kDa. Other segments encode products of 10-20 kDa in size, including a coat protein of c. 19 kDa and a protein with a retinoblastoma binding (Rb) motif.

Genera in the Family

  • Babuvirus (6 segments, with two unidirectionally transcribed ORFs on DNA1)
  • Nanovirus (8 or more monocistronic segments)