Characterization of Rice Stripe Virus: a Heavy Component Carrying Infectivity

SUMMARY Rice stripe virus (RSV) preparations contain a previously unreported nucleopro- tein component (nB) which sediments faster in sucrose gradients than middle (M) and bottom (B) components; the latter two components are 20-fold more concentrated than nB. Electron microscopy of purified nB preparations revealed filamentous particles (8 nm wide), and other structures which might be derived from these particles. The nB preparations contained four RNA species of mol. wt. 0.9 × 106, 1.0 × 106, 1.4 × 106 and 1.9 × 106 (2700, 3000, 4100 and 5600 nucleotides respectively); the three smaller RNAs may be derived from M and B components contaminating nB. A single protein (mol. wt. 3.2 × 104) was present in M, B and nB preparations. The nB component appears to be required for infectivity because the planthopper vector (Laodelphax striatellus) became viruliferous after injection with nB but not after injection with M or B.