2 DISTINCT MECHANISMS REGULATE LUTEOVIRUS TRANSMISSION EFFICIENCY ANDSPECIFICITY AT THE APHID SALIVARY-GLAND

Barley yellow dwarf luteovirus (BYDV) particles are transmitted by aph ids in a species-specific manner. Transmission to plants requires that the virus particles be transported across the basal lamina and plasma lemma of the accessory salivary gland (ASG). To characterize the role of the ASG basal lamina in regulating BYDV transmission, five aphid sp ecies were microinjected with purified New York isolates BYDV-PAV or - RPV, Both viruses associated specifically only with the ASG basal lami na, The ability of virions to penetrate the basal lamina was separate from the ability to penetrate the plasmalemma. When the salivary gland s of vector, Sitobion avenae or non-vector, Rhopalosiphum maidis, aphi ds were incubated in vitro with New York isolate BYDV-MAV, virions onl y attached to the ASG basal lamina of S. avenae. When anionic and cati onic ferritin were microinjected into aphids, only cationic ferritin a ggregated on the surface of the ASG basal lamina and at openings of pl asmalemma invaginations into the cytoplasm, suggesting that these site s had a net negative charge. In vitro studies of anionic and cationic gold penetration of ASG basal laminae indicated a macromolecular size exclusion limit of approximately 20 nm that depended on charge, Anioni c gold particles did not accumulate in the basal lamina as densely as the 25 nm BYDV particles, suggesting that the virus particles have a g reater affinity for the ASG basal lamina. These results indicate that both the ASG basal lamina and plasmalemma contain specific components independently involved in the recognition and transmission of luteovir uses.