Aphid transmission of cauliflower mosaic virus requires the viral PIII protein.
The open reading frame (ORF) III product (PIII) of cauliflower mosaic virus is necessary for the infection cycle but its role is poorly understood. We have used in vitro protein binding ('far Western') assays to demonstrate that PIII interacts with the cauliflower mosaic virus (CaMV) ORF II product (PII), a known aphid transmission factor. Aphid transmission of purified virions of the PII-defective strain CM4-184 was dependent upon added PII, but complementation was efficient only in the presence of PIII, demonstrating the requirement of PIII for transmission. Deletion mutagenesis mapped the interaction domains of PIII and PII to the 30 N-terminal and 61 C-terminal residues of PIII and PII, respectively. A model for interaction between PIII and PII is proposed on the basis of secondary structure predictions. Finally, a direct correlation between the ability of PIII and PII to interact and aphid transmissibility of the virus was demonstrated by using mutagenized PIII proteins. Taken together, these data argue strongly that PIII is a second 'helper' factor required for CaMV transmission by aphids.
Leh
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Institut de Biologie Moléculaire des Plantes, UPR CNRS 406, 12 rue du Général Zimmer, 67084 Strasbourg Cedex.
Jacquot
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Geldreich
A
A
Hermann
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T
Leclerc
D
D
Cerutti
M
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Yot
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P
Keller
M
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Blanc
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D000595:Amino Acid Sequence; D000818:Animals; D001042:Aphids / Q000821:virology*; D001483:Base Sequence; D001937:Brassica / Q000821:virology*; D002213:Capsid / Q000235:genetics / Q000378:metabolism; D036022:Capsid Proteins; D017796:Caulimovirus / Q000235:genetics / Q000502:physiology*; D003001:Cloning, Molecular; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003673:Defective Viruses / Q000235:genetics / Q000502:physiology; D004926:Escherichia coli; D005816:Genetic Complementation Test; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016366:Open Reading Frames; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014771:Virion / Q000235:genetics / Q000502:physiology
D036022:Capsid Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; D014760:Viral Fusion Proteins