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Evidence for Receptor-Mediated Endocytosis Regulating Luteovirus Acquisition by Aphids. F. E. Gildow,Associate Professor, Department of Plant Pathology, Pennsylvania State University, University Park 16802; Phytopathology 83:270-277. Accepted for publication 9 October 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-270.

The ability of five cereal grain aphid species to acquire four vector-specific isolates of barley yellow dwarf luteoviruses was tested. Aphids from New York clones of Rhopalosiphum maidis, R. padi, Schizaphis graminum, and Sitobion avenae acquired the New York type isolates of MAV, PAV, RMV, and RPV when fed on infected plants, regardless of the ability of each species to transmit the virus. Aphids from a California clone of Metopolophium dirhodum acquired MAV, PAV, and RMV, but not RPV. When R. padi and M. dirhodum were fed on 200 ?g/ml of purified RPV and examined by electron microscopy, virions of RPV were observed adsorbed to the hindgut plasmalemma and intracellularly in endocytotic vesicles only in R. padi. In M. dirhodum, RPV virions were observed free in the hindgut lumen but not adsorbed to gut membranes, and virus was not acquired. Immunolabeling was used to verify the ability of R. padi, but not M. dirhodum, to acquire RPV virions. When both species were fed on purified virions of brome mosaic virus and cowpea mosaic virus, virions were observed in high concentrations in the gut lumen but were not adsorbed to the gut membrane or incorporated into gut cells. Ultrastructural evidence of acquired virions adsorbed to the hindgut plasmalemma and in endocytotic vesicles implicates receptor-mediated endocytosis as the mechanism of luteovirus acquisition. This hypothesis is supported by evidence that virions of nonacquired viruses do not adsorb to the plasmalemma. Results suggest that recognition and adsorption of virions to the hindgut membrane is a selective step in acquisition of circulatively transmitted luteoviruses by vectors.

Additional keywords: coated vesicles, insect vectors, virus transmission.