Identification and characterization of structural proteins of orchid fleck virus

Orchid fleck virus (OFV) has a bipartite negative-sense RNA genome with sequence similarities to plant rhabdoviruses. The non-enveloped bullet-shaped particles of OFV are similar to those of the internal ribonucleoprotein (RNP)-M protein structure of rhabdoviruses, but they are about half the size of typical plant rhabdoviruses. Purified preparations contained intact bullet-shaped and filamentous particles. The filamentous particles showed a tightly coiled coil structure or a coiled structure with a helical twist, which resembles the RNP complex of rhabdoviruses. OFV bullet-shaped particles were structurally stable in solutions containing 2% Triton X-100 and 0.8 M NaCl. Western blot analyses revealed that the bullet-shaped particles contained N, P and M proteins, while filamentous particles contained mainly N and P proteins. In addition, a small amount of the L protein was detected in both types of particles. Thus, the structural proteins of OFV have properties similar to those of rhabdoviruses, except that the particles are non-enveloped and are relatively resistant to detergent-treatment under high-salt conditions.