Intracellular distribution of viral gene products regulates a complex mechanism of cauliflower mosaic virus acquisition by its aphid vector.
Interactions between Cauliflower mosaic virus (CaMV) and its aphid vector are regulated by the viral protein P2, which binds to the aphid stylets, and protein P3, which bridges P2 and virions. By using baculovirus expression of P2 and P3, electron microscopy, surface plasmon resonance, affinity chromatography, and transmission assays, we demonstrate that P3 must be previously bound to virions in order that attachment to P2 will allow aphid transmission of CaMV. We also show that a P2:P3 complex exists in the absence of virions but is nonfunctional in transmission. Hence, unlike P2, P3 and virions cannot be sequentially acquired by the vector. Immunogold labeling revealed the predominance of spatially separated P2:P3 and P3:virion complexes in infected plant cells. This specific distribution indicates that the transmissible complex, P2:P3:virion, does not form primarily in infected plants but in aphids. A model, describing the regulating role of P3 in the formation of the transmissible CaMV complex in planta and during acquisition by aphids, is presented, and its consequences are discussed.
Drucker
Martin
M
Station de Recherches de Pathologie Comparée, Unité Mixte de Recherche 5087 Institut National de la Recherche Agronomique-Centre National de la Recherche Scientifique-Université Montpellier II, 30380 Saint-Christol-lez-Alès, France.
Froissart
Remy
R
Hébrard
Eugénie
E
Uzest
Marilyne
M
Ravallec
Marc
M
Espérandieu
Pascal
P
Mani
Jean-Claude
JC
Pugnière
Martine
M
Roquet
Francoise
F
Fereres
Alberto
A
Blanc
Stéphane
S
D000818:Animals; D001042:Aphids / Q000821:virology*; D016367:Baculoviridae; D015153:Blotting, Western; D017796:Caulimovirus / Q000235:genetics*; D004279:DNA, Viral; D005822:Genetic Vectors; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D008954:Models, Biological; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors
D004279:DNA, Viral; D011994:Recombinant Proteins