Loss of potyvirus transmissibility and helper-component activity correlate with non-retention of virions in aphid stylets

• Published in: Journal of general virology Vol. 77; no. 5; pp. 861 - 867
• Main Authors: Wang, R. Y, Ammar, E. D, Thornbury, D. W, Lopez-Moya, J. J, Pirone, T. P
• Format: Journal Article
• Language: English
• Published: England Soc General Microbiol 01.05.1996
• Subjects: Amino Acid Sequence; Animals; Aphididae; Aphids - virology; Homoptera; Insect Vectors - virology; Microscopy, Electron; Molecular Sequence Data; potato virus Y; Potyvirus - physiology; Potyvirus - ultrastructure; tobacco etch virus; tobacco vein mottling virus; Viral Proteins - physiology; Virion - physiology
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/0022-1317-77-5-861

Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA The hypothesis that loss of aphid transmissibility of potyvirus mutants is due to non-retention of virions in the mouthparts was tested by feeding aphids through membranes on purified virions of aphid transmissible (AT or HAT) and non-aphid-transmissible (NAT) tobacco vein mottling virus (TVMV) or tobacco etch virus (TEV), in the presence of functional [potato virus Y (PVY) HC or TVMV HC] or non-functional (PVC HC) helper component (HC). TVMV virions were detected, by electron microscopic examination of immunogold-labelled thin sections, in the food canal or cibarium of 57% of 28 aphids fed on the transmissible combination of TVMV-AT and functional HC, while no virions were found in these structures in 25 aphids fed on the non-transmissible combinations: TVMV-NAT and PVY HC, or TVMV-AT and PVC HC. Autoradiography of intact stylets allowed the examination of much larger numbers of aphids, fed on 125 I-labelled TEV; 48% of 523 aphids fed on the TEV-HAT and PVY HC combination retained label in the stylets; this correlated well with the percentage transmission in bioassays. In contrast, in non-transmissible combinations, label was found in the stylets of 0·77% of 389 aphids fed on TEV-NAT and PVY HC, and 1·35% of 223 aphids fed on TEV-HAT and PVC HC. No differences were found in the overall amount of label in the bodies of aphids fed on the transmissible and non-transmissible combinations. There was a strong tendency for virions to be retained in the distal third of the stylets; 56% of aphids positive for TVMV, and 82% of those positive for TEV, had label in this area. These data support the concept that virions retained within the stylets are those that are primarily involved in potyvirus transmission. * Author for correspondence. Fax +1 606 323 1961. e-mail ppa133@ukcc.uky.edu Received 3 November 1995; accepted 19 January 1996.