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Mutagenesis of a hexanucleotide sequence conserved in potexvirus RNAs.
K A White1, J B Bancroft, G A Mackie
1Department of Biochemistry, University of Western Ontario, London, Canada.
Virology
|August 1, 1992
Summary
A conserved hexanucleotide motif is essential for clover yellow mosaic virus (CYMV) defective RNA (D RNA) accumulation. This sequence is crucial for viral RNA synthesis in potexviruses and carlaviruses.
Area of Science:
- Molecular Virology
- Plant Pathology
- RNA Biology
Background:
- Potexvirus RNAs feature a conserved 3' noncoding hexanucleotide motif (5'-ACUUAA).
- This motif's role in viral RNA replication and accumulation remains largely unelucidated.
Purpose of the Study:
- To investigate the essentiality of the conserved hexanucleotide motif for clover yellow mosaic virus (CYMV) defective RNA (D RNA) accumulation.
- To determine the functional significance of this motif in viral RNA synthesis.
Main Methods:
- Synthesis of biologically active in vitro transcripts of CYMV D RNA.
- Deletion and single-base substitution mutagenesis of the hexanucleotide motif.
- Coinoculation experiments with helper CYMV RNA and analysis of progeny D RNA accumulation in planta.
Main Results:
- Complete deletion or rearrangement of the hexanucleotide motif abolished D RNA accumulation.
- Single-base substitutions were tolerated only at specific positions (3 and 5) within the motif.
- The hexanucleotide sequence was identified in promoter regions for subgenomic RNA (sgRNA) in potexvirus and carlavirus negative strands.
Conclusions:
- The conserved hexanucleotide motif is critical for D RNA propagation in CYMV.
- This sequence functions as a cis-acting element essential for both full-length negative-sense RNA and positive-sense sgRNA synthesis.
- The motif's conservation across potexviruses and carlaviruses highlights its fundamental role in viral RNA replication.