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Comparison of the p26 gene region of two baculoviruses
J N Bicknell1, D J Leisy, G F Rohrmann
1Department of Agricultural Chemistry, Oregon State University, Corvallis 97331.
Abstract:
A 1.1-kb region of DNA containing the p26 gene of the multicapsid nuclear polyhedrosis virus of Orgyia pseudotsugata (OpMNPV) was sequenced, transcriptionally mapped, and compared to the same region in the MNPV of Autographa californica (AcMNPV). The mRNA start site of the p26 gene occurs about 22 nucleotides downstream from an A/T-rich putative promoter sequence that is highly conserved between AcMNPV and OpMNPV. The p26 mRNA is transcribed through the p26 gene and coterminates with the p10 gene resulting in a mRNA containing copies of both genes. The reading frames of the OpMNPV and AcMNPV p26 genes showed 47% amino acid sequence homology which is clustered in six regions with over 65% amino acid homology. There was a distinct bias toward incorporation of G/C-rich codons in the OpMNPV p26 gene. No DNA homology was observed between the region upstream of the p26 gene in AcMNPV and OpMNPV. In AcMNPV, this region contains the homologous repeated (hr) sequence hr5. Hybridization of a plasmid containing an AcMNPV-repeated sequence (hr5) to Southern blots of the OpMNPV genome indicated that this repeated sequence is lacking in OpMNPV.
Insights
The p26 gene in Orgyia pseudotsugata multicapsid nuclear polyhedrosis virus (OpMNPV) shares conserved promoter regions and clustered homology with Autographa californica MNPV (AcMNPV). However, OpMNPV lacks the hr5 sequence found upstream of the p26 gene in AcMNPV.
Area of Science:
- Molecular Virology
- Insect Pathology
- Genomics
Background:
- The p26 gene is crucial in baculovirus replication and pathogenesis.
- Comparative genomics of baculoviruses aids in understanding viral evolution and gene function.
Purpose of the Study:
- To sequence and transcriptionally map the p26 gene region of Orgyia pseudotsugata MNPV (OpMNPV).
- To compare this region with the homologous region in Autographa californica MNPV (AcMNPV).
- To identify conserved and divergent elements between these two baculoviruses.
Main Methods:
- DNA sequencing of a 1.1-kb region containing the OpMNPV p26 gene.
- Transcriptional mapping to determine mRNA start sites and termination.
- Sequence comparison and homology analysis between OpMNPV and AcMNPV p26 genes.
- Southern blot hybridization to detect homologous repeated (hr) sequences.
Main Results:
- A conserved A/T-rich promoter sequence upstream of the p26 mRNA start site was identified in both OpMNPV and AcMNPV.
- The p26 mRNA in OpMNPV coterminates with the p10 gene, forming a bicistronic mRNA.
- OpMNPV p26 gene exhibits 47% amino acid homology with AcMNPV p26, clustered in six regions with >65% homology.
- OpMNPV p26 gene shows a bias towards G/C-rich codons.
- The hr5 homologous repeat sequence, present upstream of the p26 gene in AcMNPV, is absent in OpMNPV.
Conclusions:
- The p26 gene and its regulatory regions show significant conservation between OpMNPV and AcMNPV, suggesting functional importance.
- Differences in codon usage and the absence of hr5 in OpMNPV indicate distinct evolutionary paths or regulatory mechanisms.
- The bicistronic transcription of p26 and p10 in OpMNPV highlights variations in gene expression strategies within baculoviruses.