Molecular Analysis of the Essential and Nonessential Genetic Elements in the Genome of Peanut Chlorotic Streak Caulimovirus

The DNA genome of caulimoviruses contains a set of essential genes: I (movement gene), IV (major capsid protein gene), V (reverse transcriptase gene), and VI (gene coding for a post-transcriptional activator of the expression of other virus genes). In peanut chlorotic streak caulimovirus (PCISV), th...

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Bibliographic Details
Published in:Virology (New York, N.Y.) N.Y.), 1995-02, Vol.206 (2), p.823-834
Main Authors: Mushegian, A.R., Wolff, J.A., Richins, R.D., Shepherd, R.J.
Format: Article
Language:English
Subjects:
Arachis - virology
Base Sequence
Capsid - genetics
Caulimovirus - genetics
Caulimovirus - metabolism
Caulimovirus - pathogenicity
Cloning, Molecular
DNA Primers
DNA, Viral - genetics
DNA, Viral - isolation & purification
Genes, Lethal
Genome, Viral
Molecular Sequence Data
Mutagenesis
Mutagenesis, Insertional
Open Reading Frames
peanut chlorotic streak virus
Plant Diseases
Plasmids
Polymerase Chain Reaction
Restriction Mapping
RNA-Directed DNA Polymerase - genetics
Sequence Deletion
Trans-Activators - genetics
Virion - genetics
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Summary:The DNA genome of caulimoviruses contains a set of essential genes: I (movement gene), IV (major capsid protein gene), V (reverse transcriptase gene), and VI (gene coding for a post-transcriptional activator of the expression of other virus genes). In peanut chlorotic streak caulimovirus (PCISV), three ORFs, A, B, and C, are located between genes I and IV. They are dissimilar to other caulimovirus ORFs. ORF VII of PCISV is a homolog of ORF VII of soybean chlorotic mottle caulimovirus (SoCMV), but is not similar to the nonconserved ORF VII in other caulimoviruses. The sequence complementary to a portion of tRNAMet, thought to be essential for the priming of minus-strand DNA synthesis in caulimoviruses, is located within the coding sequence of ORF A. To explore the functional significance of ORFs VII, A, B, and C, various mutations were engineered into an infectious DNA clone of PCISV. ORFs VII and B are shown to be dispensable, while ORFs A and C are essential. ORF C is a possible functional equivalent of gene III in other caulimoviruses. Sequences within ORF A that are required for efficient priming of minus-strand synthesis are likely to extend beyond the 12-bp tRNA-binding site. Complete deletion of ORF VII was correlated with severe symptoms, notably with the necrosis of apical meristems. Significance of these observations for the understanding of replication and pathogenesis of plant pararetroviruses and for the improvement of caulimovirus-based expression vectors is discussed.
ISSN:0042-6822
1096-0341
DOI:10.1006/viro.1995.1005