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Structural diversity and conservation among CRESS-DNA bacilladnaviruses revealed through cryo-EM and computational
L Johanna Gebhard1, Yuji Tomaru2, Kenta Okamoto1
1Laboratory of Molecular Biophysics, Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.
Virology Journal
|December 2, 2025
Summary
Researchers determined the capsid structure of a single-stranded DNA virus infecting diatoms, revealing key differences from related viruses and insights into viral evolution. This study expands understanding of Bacilladnaviridae structural diversity and evolution.
Area of Science:
- Virology
- Structural Biology
- Marine Microbiology
Background:
- Viruses infecting microalgae play crucial roles in marine ecosystems, influencing growth, community structure, and nutrient cycling.
- The Bacilladnaviridae family, comprising single-stranded DNA viruses, infects marine diatoms and is important for understanding viral evolution.
- Diatom viruses offer insights into early viral evolution due to their unique genetic makeup and ecological impact.
Purpose of the Study:
- To determine the capsid structure of Chaetoceros lorenzianus DNA virus (ClorDNAV).
- To expand the understanding of structural diversity within the ssDNA virus phylum Cressdnaviricota.
- To investigate the evolutionary relationship between Bacilladnaviridae and other viruses.
Main Methods:
- X-ray crystallography was used to determine the high-resolution (2.2 Å) capsid structure of ClorDNAV.
- Low-resolution genome reconstruction was performed to visualize DNA packaging.
- Comparative structural analysis was conducted between ClorDNAV and other Bacilladnaviridae viruses, including AlphaFold3-predicted structures.
Main Results:
- The ClorDNAV capsid protein exhibits a conserved jelly-roll fold with a surface-exposed projection domain.
- Structural comparison revealed five key differences between ClorDNAV and CtenDNAV-II, including variations in terminal regions and domain structures.
- Analysis of predicted structures across Bacilladnaviridae genera confirmed fold conservation but highlighted variability in surface and terminal regions, suggesting host-specific adaptations.
Conclusions:
- The determined structure of ClorDNAV expands the known structural diversity within Bacilladnaviridae.
- Structural findings provide evidence for the evolution of ssDNA Bacilladnaviridae from ssRNA ancestors.
- Comparative analysis of experimental and predicted structures offers a comprehensive view of structural conservation and divergence within the Bacilladnaviridae family.
Keywords:
Algal virusBacilladnaviridaeCRESS-DNA virusCapsid structureClorDNAVCryo-electron microscopyGenome packagingIcosahedral virusJelly-roll foldSingle-stranded DNA virusMore Related Videos
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