Translation of Cymbidium Ringspot Virus RNA in Cowpea Protoplasts and Rabbit Reticulocyte Lysates

Abstract

Summary RNA from cymbidium ringspot virus (CyRSV), a tombusvirus, was translated in rabbit reticulocyte lysates and in vitro translation products were compared with virus-specific proteins in extracts of cowpea protoplasts inoculated with virus particles. Four major polypeptides were produced in vitro, with molecular weights of 43000 (43K), 40K, 34K and 22K, and three were produced in vivo, with molecular weights of 45K, 43K and 22K. The 43K and probably also the 22K product were the same in vitro and in vivo; the former was definitely identified as the virus coat protein. The 45K protein was a modified coat protein found only in extracts of infected protoplasts that had been frozen. Translation experiments with size-fractionated RNA indicated that the translation strategy of CyRSV RNA involved, as templates, both genome-size RNA (40K product) and subgenomic species (43K, 34K and 22K products). The presence of at least three coding regions on the virus genome was suggested by comparative peptide mapping of the four major translation products. No infection-specific polypeptides or translation products were detected as specific to satellite RNA, either in inocula for protoplasts or in RNA added to reticulocyte lysates.