The Role of AV2 (“Precoat”) and Coat Protein in Viral Replication and Movement in Tomato Leaf Curl Geminivirus

We analyzed various mutants of tomato leaf curl virus-India to investigate the role of ORFs AV3, AV2, and coat protein (CP) in viral replication, movement, and symptom development. The results of these studies indicate that ORF AV3 does not encode a protein. Plants inoculated with infectious DNA whi...

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Bibliographic Details
Published in:Virology (New York, N.Y.) N.Y.), 1996-10, Vol.224 (2), p.390-404
Main Authors: Padidam, Malla, Beachy, Roger N., Fauquet, Claude M.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Base Sequence
Capsid - genetics
Capsid - physiology
DNA Replication
DNA, Single-Stranded - metabolism
DNA, Viral - metabolism
Geminiviridae - genetics
Geminiviridae - physiology
Molecular Sequence Data
Mutagenesis
Nicotiana
Open Reading Frames
Plants, Toxic
Protoplasts
Rabbits
Sequence Deletion
Sequence Homology, Amino Acid
Solanum lycopersicum - virology
Virus Replication
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Summary:We analyzed various mutants of tomato leaf curl virus-India to investigate the role of ORFs AV3, AV2, and coat protein (CP) in viral replication, movement, and symptom development. The results of these studies indicate that ORF AV3 does not encode a protein. Plants inoculated with infectious DNA which contained deletions in AV2 developed very mild symptoms and accumulated only low levels of both single-stranded (ss) and double-stranded (ds) viral DNA, whereas inoculated protoplasts accumulated both ss and dsDNA to wild-type levels, showing that AV2 is required for efficient viral movement. However, both plants and protoplasts inoculated with substitution, frameshift, and other similar mutations in AV2 accumulated low levels of viral DNA. The low levels of accumulation of DNA of these mutants were apparently not due to a defect in AV2 synthesis. Mutations in the CP caused a marked decrease in ssDNA accumulation in plants and protoplasts while increasing dsDNA accumulation in protoplasts. Mutations in both AV2 and CP behaved like AV2 mutants in plants and like CP mutants in protoplasts. The results demonstrated that multiple functions provided by AV2, BV1, and BC1 are essential for viral movement, and that changes in A-component virion-sense mRNA structure or translation affect viral replication.
ISSN:0042-6822
1096-0341
DOI:10.1006/viro.1996.0546