STRUCTURAL DIFFERENCES BETWEEN PEA ENATION MOSAIC-VIRUS STRAINS AFFECTING TRANSMISSIBILITY BY ACYRTHOSIPHON-PISUM (HARRIS)

Aphid-transmissible and non-aphid-transmissible strains of pea enation mosaic virus were compared in biological and physical properties. When separated by electrophoresis into 3.4% polyacrylamide gels both centrifugal components of aphid-transmissible strains gave rise to multiple-banding, whereas non-aphid-transmissible strains migrated as two components without separation into multiple bands. The multiple banding phenomenon during gel electrophoresis may be caused by the association of different amounts of an additional protein of 56,000 daltons with the virions, so that they migrate as different size classes. The mean increment between the diameters of any two size classes was determined to be 0.54 nm. The origin of this second coat protein may be accounted for by the molecular weight of the largest viral RNA from a transmissible strain being 1.2 × 105 daltons larger than that of the non-aphid-transmissible strains. A non-aphid-transmissible strain could be selected by continuous mechanical passages of an aphid-transmissible strain and resembled other non-aphid-transmissible strains in all characteristics tested, including the lack of the second protein associated with virions. Hence, it is postulated that the second protein, unique to aphid-borne strains, is a gene product responsible for the insect transmission of PEMV. For both aphid-transmissible and non-aphid-transmissible strains of PEMV, examination of the RNA content of the two nucleoproteins largely confirmed the recent work of others on the multipartite nature of the virus genom. Evidenc is presented genome. Evidence is presented for RNA3 arising as a breakage product of RNA1 during isolation with phenol-SDS. © 1979.