Component proteins and structure of rice ragged stunt virus

Rice ragged stunt virus (RRSV) particles consist of a polyhedral core particle approx. 50 nm in diameter to which are attached flat spikes about 20 nm wide and 10 nrn high, giving a total diameter of about 70 nm. Polyacrylamide gel electrophoresis of disrupted particles of RRSV gave five major polypeptides with tool. wt. of 145000 (145K), 137K, 72K, 47K and 37K. Core particles prepared by suspending particles in 0.5 M-MgCI2 contained the 145K, 137K, 72K proteins and relatively small amounts of the 37K protein, whereas the supernatant fluid recovered after centrifugation of the core particles contained the 47K and 37K proteins. The results suggest that the 145K, 137K and 72K proteins are core proteins and one or both of the 47K and 37K proteins are components of the spike. Immunoblotting experiments indicated that all the proteins are recognized as antigens, suggesting that RRSV particles are less stable than those of the phytoreoviruses, rice dwarf and rice gall dwarf viruses. Rice ragged stunt virus (RRSV) causes a disease in rice and is transmitted in a persistent manner by brown planthoppers (Hibino et al., 1977; Ling et al., 1978; Boccardo & Milne, 1984). The genome of RRSV comprises 10 segments of double-stranded RNA (Omura et al., 1983; Boccardo & Milne, 1984). No information has been reported on the structural proteins of RRSV presumably because it is difficult to obtain purified preparations. The numbers, sizes and location in the virus particle of plant reovirus structural proteins have been determined for wound tumour virus (Reddy & Macleod, 1976), rice dwarf virus (RDV) (Nakata et al., 1978)