Purification of rice dwarf virus

Abstract

The electron micrograph of rice dwarf virus (RDV) given by Fukushi, Shikata, and Kimura1) shows that RDV particles are enveloped with a membranaceous material. A fraction containing similar RDV particles was obtained from infected rice leaves by treating the expressed sap with 10 to 20per cent chloroform and the same differential cenrifugation procedure as adopted by Fukushi et al1). RDV in this fraction was so firmly adsorbed by DEAE-cellulose column that it could not be eluted with increasing concentration of NaCl from 0 to 1.0M, but was eluted only with 0.5M NaOH, suggesting that the virus particles were covered with some strongly acidic substance, possibly the enveloping material. This material was easily removed by treating the fraction with phospholipase of snake venom or pancreatin. After this treatment, RDV was eluted from DEAE-cellulose column with 0.2 to 0.25M NaCl. RDV in the effluent showed typical morphological characteristics, an icosahedron with hollow capsomeres, when examined under electron microscope. Electrophoretic and sedimentation patterns of the effluent showed that the preparation consisted of homogeneous RDV particles. The purified RDV retained infectivity to rice plants when assayed through the insect vector, Nephotettix cincticeps Uhler.