Virus-vector cell interactions regulating transmission specificity of soybean dwarf luteoviruses

Transmission of soybean dwarf viruses (SbDV) indigenous to Japan (SbDV-D) a nd to the eastern United States (SbDV-Va20) were compared in vector and non vector aphid species. Absolute vector-specificity was maintained when Aulac orthum solani, Acythosiphon pisum, and Myzus persicae were allowed to feed on solutions of either virus (100 mu g/ml) through Parafilm(C) membranes. S bDV-D was transmitted only by A. solani, and SbDV-Va20 was transmitted only by A. pisum and ill. persicae. Similar results were obtained when individu al aphids were microinjected with 2 ng virus and subsequently allowed to fe ed on healthy plants. Ultrastructural studies of A. solani and M. persicae indicated that both SbDV-D and SbDV-Va20 were acquired specifically through the aphid hindgut. No difference in hindgut acquisition specificity was ob served, and both A. solani and M. persicae were able to transport SbDV-D an d SbDV-Va20 into the haemocoel by endocytotic/exocytotic pathways. When inj ected, SbDV was shown to be associated with only the accessory salivary gla nds (ASG) in aphids, indicating a high level of tissue specificity. Two dif ferent interactions with the ASG were observed for SbDV-D and SbDV-Va20 in A. solani and M. persicae. SbDV-D penetrated the ASG basal lamina of A. sol ani, but was never observed in the basal lamina of M. persicae. The ASG bas al lamina was a barrier to SbDV-D transmission by M. persicae. SbDV-Va20 pe netrated the ASG basal lamina of both A. solani and hi. persicae. However, SbDV-Va20 was not observed in the ASG cytoplasm in A. solani, indicating th at the basal plasmalemma functioned as the transmission barrier. Observatio ns indicated that capsid protein structure, aphid basal lamina composition and cell membrane components influenced virus-aphid interactions regulating SbDV transmission.