Insect cypoviruses: advances in structural characterization, evolutionary genomics, and host interaction dynamics.

Area of Science:

• Virology
• Genomics
• Insect Pathology

Background:

• Cypoviruses are insect-specific double-stranded RNA viruses.
• They belong to the genus Cypovirus within the family Spinareoviridae.
• These viruses infect Lepidoptera, Diptera, and Hymenoptera, replicating in midgut cells and forming polyhedra.

Purpose of the Study:

• To conduct a comprehensive comparative genomic analysis of representative Cypovirus species.
• To focus on segment-wise gene assignments and identify conserved protein domains and motifs.
• To establish practical criteria for rapid Cypovirus species identification.

Main Methods:

• Comparative genomic analysis of Cypovirus species.
• Segment-wise assignment of viral protein functions.
• Analysis of nonsynonymous to synonymous substitution (Ka/Ks) ratios.
• Phylogenetic analysis to understand lineage diversification.

Main Results:

• Segment 1 universally encodes the major capsid protein; Segment 2 encodes RNA-dependent RNA polymerase (RdRP); Segment 3 encodes the minor capsid protein.
• Segments 4-5 encode RNA capping enzymes; Segments 6-10 encode other structural or non-structural proteins, including polyhedrin.
• Evidence of purifying and positive selection identified across genomic segments.
• Genotypic and phenotypic variability correlates with host, co-infection, and geographic isolation.

Conclusions:

• Established a reference framework for rapid Cypovirus species identification using genomic demarcation criteria.
• Provided structural, genomic, and evolutionary insights into Cypovirus biology and diversity.
• Highlighted functional convergence in protein roles across species despite genotypic variability.