Two Purified RNAs of Soil-borne Wheat Mosaic Virus are Needed for Infection

Abstract

RNA of soil-borne wheat mosaic virus (SBWMV) from virions 281 nm and 92 nm long (designated here by relative lengths as 1.0 L, 0.5 L and 0.35 L, respectively), were isolated and purified by 3 cycles of sucrose density gradient centrifugation. Infectivity assays with these RNA proved the bipartite nature of SBWMV, the combination of 1.0 L and either 0.5 L or 0.35 L RNA being required for infection and for multiplication of progeny viruses. The 0.5 L RNA underwent deletion mutation, producing smaller variants with various sizes, of which 0.4 L and 0.35 L RNA were confirmed to be functional in combination with 1.0L RNA. The coat proteins of all isolates had MW of 19,700. The MW of 1.0 L. 0.5 L, 0.4 L and 0.35 L RNA, determined under denaturing conditions, were 2.28 .times. 106 (6500 bases), 1.23 .times. 106 (3500 bases), 0.97 .times. 106 (2800 bases) and 0.86 .times. 106 (2450 bases), respectively. A new virus group, furovirus (fungus-borne rod-shaped virus), is proposed for SBWMV.