Specificity and properties of the genome-linked proteins of nepoviruses

Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, U.K. The infectivity of the RNA of six nepoviruses was decreased or abolished by proteinase K treatment, whereas that of the RNA of cowpea mosaic virus (comovirus group) or tomato bushy stunt virus was unaffected. The extent of the decre...

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Bibliographic Details
Published in:Journal of general virology 1982-01, Vol.59 (1), p.149-162
Main Authors: Mayo, M.A, Barker, H, Harrison, B.D
Format: Article
Language:English
Subjects:
Comovirus
nepovirus
raspberry ringspot virus
strawberry latent ringspot virus
tobacco ringspot virus
tomato black ring virus
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Summary:Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, U.K. The infectivity of the RNA of six nepoviruses was decreased or abolished by proteinase K treatment, whereas that of the RNA of cowpea mosaic virus (comovirus group) or tomato bushy stunt virus was unaffected. The extent of the decrease in infectivity was characteristic for each nepovirus and was independent of the plant species used as virus source or as assay host. The infectivity of raspberry ringspot virus (RRV) RNA was less affected than that of the other nepoviruses but treatment with Pronase decreased infectivity more than treatment with proteinase K. Proteinase K treatment also abolished the infectivity for tobacco mesophyll protoplasts of RNA of tobacco ringspot virus (TRSV) and tomato black ring virus (TBRV). Tests on virus RNA, labelled with 125 I by the chloramine T method, provided evidence that three nepoviruses and Echtes Ackerbohnenmosaik-Virus (EAMV; comovirus group) have genome-linked proteins (VPg). Pronase treatment rendered about half (RNA of strawberry latent ringspot virus; SLRV), or nearly all (RNA of the other nepoviruses and EAMV), of the 125 I soluble in 70% ethanol. Treatment of nepovirus RNA with ribonuclease P1 yielded a product with an estimated mol. wt. of 4000 ± 900. Mobilities in polyacrylamide gels of VPg from the RNA of different viruses differed slightly (SLRV > TBRV > TRSV > RRV). TRSV VPg yielded one 125 I-labelled tryptic peptide whereas the genome-linked proteins of RRV and TBRV both yielded two major products, of which one was resistant to further digestion and the other was converted, apparently via intermediates, to a second more stable product. No difference was detected between the tryptic peptides obtained from VPg of different strains of RRV, or of TBRV, or between those obtained from RNA-1, RNA-2 or RNA-3 (satellite RNA) of TBRV. Nepovirus VPg is therefore virus-specific. It seems to be coded on RNA-1 and probably has multiple functions. Keywords: nepovirus, RNA infectivity, genome-linked protein, protease Received 28 July 1981; accepted 15 October 1981.
ISSN:0022-1317
1465-2099
DOI:10.1099/0022-1317-59-1-149