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Association of Potyvirus Helper Component Protein with Virions and the Cuticle Lining the Maxillary Food Canal and Foregut of an Aphid Vector. E. D. Ammar, Department of Plant Pathology, University of Kentucky, Lexington 40546; U. Järlfors, and T. P. Pirone. Department of Plant Pathology, University of Kentucky, Lexington 40546. Phytopathology 84:1054-1060. Accepted for publication 23 June 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-1054.

Transmission electron microscopy and immunogold labeling were used to study the role of the helper component protein (HC) that is required for the transmission of potyviruses by aphids. Purified tobacco etch virus (TEV) and tobacco vein mottling virus (TVMV) were fed to the aphid vector, Myzus persicae, either with or without purified HC. In sections of aphids that fed on a mixture of purified virions and HC, filamentous viruslike particles (VLP) embedded in a matrix material were associated with the epicuticle, predominantly in the maxillary food canal but also in the precibarium and cibarium of the foregut. No VLP were found at any of these sites in aphids that fed on purified virions without HC. Immunogold labeling demonstrated that the VLP are TEV or TVMV virions and that HC is associated with virions and with the epicuticle lining the food canal and foregut. These results support the hypothesis that HC is directly involved in binding or attachment of virions to the cuticle of the maxillary food canal and foregut of aphid vectors.