Poster: Epidemiology: Pathogen-Vector Interations
Molecular interactions between citrus tristeza virus and its aphid vector, Toxoptera citricida
N. KILLINY (1), S. Harper (2), C. C. El Mohtar (2), B. Dawson (2) (1) University of Florida, IFAS, CREC, Department of Plant Pathology, U.S.A.; (2) University of Florida, Department of Plant Pathology, U.S.A.
Citrus tristeza virus is transmitted by several aphid species, including Aphis gossypii, Aphis spiraecola, Toxoptera aurantii, and Toxoptera citricida. Considerable variations in the efficacy of transmission both among different vector species, and among CTV isolates are recorded. T. citricida, the brown citrus aphid, is the most efficient and specialized vector. It has a host range limited primarily to rutaceous species and transmits most CTV isolates at higher rates than other aphids. We demonstrated that CTV binds specifically to the lining of the cibarium of the aphid using fluorescently-labelled virions. In vitro competitive-binding assays between fluorescent virions and free viral proteins determined that the minor coat protein and two heat-shock-like proteins (p61 and p65) are involved in vector interaction. Treating the dissected mouthparts with proteases prior to the binding assay did not affect the binding of CTV virions while, chitinase treatment reduced the CTV binding to foregut. These findings suggest that CTV binds to sugar moieties of the cuticular surface of the aphid cibarium and not to embedded proteins. Additionally, the specific binding involves the concerted activity of three virally-encoded proteins.