Phytoreovirus

Phytoreoviruses are non-turreted reoviruses that are major agricultural pathogens, particularly in Asia. One member of this family, Rice Dwarf Virus (RDV), has been extensively studied by electron cryomicroscopy and x-ray crystallography. From these analyses, atomic models of the capsid proteins and a plausible model for capsid assembly have been derived. While the structural proteins of RDV share no sequence similarity to other proteins, their folds and the overall capsid structure are similar to those of other Reoviridae.

Phytoreoviruses are unique among Reoviridae in that there are 12 dsRNA segments in each virus. Like all other Reoviridae, they contain their own RNA-dependant RNA polymerase, allowing for endogenous synthesis of viral mRNA within the virus. Although less well studied than orthoreovirus and orbivirus, considerable structural and biochemical studies have been undertaken to characterize phytoreoviruses, which in general infect plants. There are three recognized phytoreoviruses: wound tumour virus (WTV), rice dwarf virus (RDV) and rice gall dwarf virus (RGDV). Possible additional family members include tobacco leaf enation virus (TLEF), rice bunchy stunt virus and sweet potato virus (ICTV, VIDE). There are also several RDV isolates, all of which share over 90% sequence identity. Of these phytoreoviruses, RDV has been extensively studied and is the best characterized member. Most of our knowledge about phytoreovirus assembly and structure is based on structural data accumulated in RDV studies.