Non-enveloped icosahedral capsid, about 50 nm in diameter. Presumably T=1 icosahedral symmetry but has not been determined.


Segmented linear dsRNA genome: 2 segments encoding potentially for 4 proteins. Segments are about 7 kb and 9 kb.


The coding strands of RNA-1 and RNA-2 contain two tandem non-overlapping ORFs. A single major capsid protein of 135 kDa is encoded by RNA-1.



  1. Virus penetrates into the cytoplasm.
  2. Transcription of the dsRNA genome by viral polymerase occurs inside the virion, so that dsRNA is never exposed to the cytoplasm. This plus-strand transcript is used as template for translation.
  3. (+)RNAs are encapsidated in virion particle, in which they are transcribed to give RNA (-) molecules with which they become base-paired to produce dsRNA genomes.
  4. Mature are transmitted to new cell during cell division, sporogenesis or cell fusion.