Bluetongue virus assembly and morphogenesis.

Like other members of the Reoviridae, bluetongue virus faces the same constraints on structure and assembly that are imposed by a large dsRNA genome. However, since it is arthropod-transmitted, BTV must have assembly pathways that are sufficiently flexible to allow it to replicate in evolutionarily distant hosts. With this background, it is hardly surprising that BTV interacts with highly conserved cellular pathways during morphogenesis and trafficking. Indeed, recent studies have revealed striking parallels between the pathways involved in the entry and egress of nonenveloped BTV and those used by enveloped viruses. In addition, recent studies with the protein that is the major component of the BTV viroplasm have revealed how the assembly and, as importantly, the disassembly of this structure may be achieved. This is a first step towards resolving the interactions that occur in these virus 'assembly factories'. Overall, this review demonstrates that the integration of structural, biochemical and molecular data is necessary to fully understand the assembly and replication of this complex RNA virus.