Virus-Vector Cell Interactions Regulating Transmission Specificity of Soybean Dwarf Luteoviruses

Transmission of soybean dwarf viruses "SbDV# indigen! ous to Japan "SbDV!D# and to the eastern United States "SbDV!Va19# were compared in vector and nonvector aphid species[ Absolute vector!speci_city was maintained when Aulacorthum solani\ Acyrthosiphon pisum\ and Myzus persicae were allowed to feed on solutions of either virus "099 mg:ml# through Para_lm membranes[ SbDV! D was transmitted only by A[ solani\ and SbDV!Va19 was transmitted only by A[ pisum and M[ persicae[ Similar results were obtained when individual aphids were micro! injected with 1 ng virus and subsequently allowed to feed on healthy plants[ Ultrastructural studies of A[ solani and M[ persicae indicated that both SbDV!D and SbDV! Va19 were acquired speci_cally through the aphid hindgut[ No di}erence in hindgut acquisition speci_city was observed\ and both A[ solani and M[ persicae were able to transport SbDV!D and SbDV!Va19 into the haemocoel by endocytotic:exocytotic pathways[ When injected\ SbDV was shown to be associated with only the accessory salivary glands "ASG# in aphids\ indicating a high level of tissue speci_city[ Two di}erent interactions with the ASG were observed for SbDV!D and SbDV! Va19 in A[ solani and M[ persicae[ SbDV!D penetrated the ASG basal lamina of A[ solani\ but was never observed in the basal lamina of M[ persicae[ The ASG basal lamina was a barrier to SbDV!D transmission by M[ persicae[ SbDV!Va19 penetrated the ASG basal lam! ina of both A[ solani and M[ persicae[ However\ SbDV! Va19 was not observed in theASG cytoplasm in A[ solaniindicating that the basal plasmalemma functioned as the transmission barrier[ Observations indicated that capsid protein structure\ aphid basal lamina composition and U[ S[ Copyright Clearance Center Code Statement] 9820 0674:1999:3795 9222 , 04[99:9 cell membrane components in~uenced virus aphid inter! actions regulating SbDV transmission[