Shared and species-specific features among ichnovirus genomes

Area of Science:

• Virology
• Genomics
• Entomology

Background:

• Endoparasitic wasps transmit polydnaviruses to caterpillars, altering host physiology to benefit wasp larvae.
• Polydnavirus taxa, ichnovirus (IV) and bracovirus (BV), possess large, segmented dsDNA genomes with expanded gene families.
• Previous IV genome analysis relied heavily on a single species (CsIV), limiting comparative insights.

Purpose of the Study:

• To analyze and compare the genomes of two additional ichnoviruses: Hyposoter fugitivus IV (HfIV) and Tranosema rostrale IV (TrIV).
• To identify conserved features and interspecific variations across three IV genomes (CsIV, HfIV, TrIV).
• To explore how genomic differences may relate to parasite/host biology and virus-induced pathologies.

Main Methods:

• Genome sequencing and comparative analysis of HfIV and TrIV.
• Comparison of HfIV and TrIV genome sequences with the previously reported CsIV genome.
• Identification and characterization of conserved and unique gene families across the three IV genomes.

Main Results:

• The three IV genomes share conserved features: low coding density, A+T bias, ~250 kb size, and nested segments.
• All analyzed IV genomes contain six conserved gene families: repeat element, cysteine motif, viral innexin, viral ankyrin, N-family, and polar-residue-rich proteins.
• Significant interspecific variations were observed in genome segmentation, gene family frequencies, and the presence of a unique gene family (TrV) in TrIV.

Conclusions:

• Comparative genomic analysis reveals both conserved elements and significant divergence among ichnovirus species.
• Interspecific genomic variations likely reflect adaptations to specific parasite-host interactions and resulting pathologies.
• The study expands the understanding of IV diversity and provides a foundation for future research into polydnavirus evolution and function.