In this study, Dendrolimus punctatus tetravirus (DpTV) has been identified as a new member of the genus Omegatetravirus of the family Tetraviridae that may be related serologically to Nudaurelia capensis v virus (NvV). DpTV particles are isometric, with a diameter of about 40nm and a buoyant density of 1?281 g cm3 in CsCl. The virus has two capsid proteins (of 62 500 and 6800 Da) and two single-stranded RNA molecules (RNA1 and RNA2), which are 5492 and 2490 nt long, respectively. RNA1 has a large open reading frame (ORF) encoding a polypeptide of 180 kDa; RNA2 contains two partially overlapping ORFs encoding polypeptides of 17 and 70 kDa. The 180 kDa protein, which contains consensus motifs of a putative methyltransferase, helicase and RNA-dependent RNA polymerase, shows significant similarity to those of other tetraviruses. The 17 kDa protein is a PEST (Pro/Glu/Ser/Thr) protein of unknown function. The 70 kDa protein is the coat protein precursor and is predicted to be cleaved at an Asn-Phe site located after residue 570. The 70 kDa protein shows 86 and 66% identity to its homologues in NvV and Helicoverpa armigera stunt virus, respectively. Secondary-structure analysis revealed that the RNAs of DpTV have tRNA-like structures at their 39 termini.