Fungal DNA virus infects a mycophagous insect and utilizes it as a transmission vector

Area of Science:

• Mycology
• Virology
• Entomology
• Plant Pathology

Background:

• Mycoviruses are typically transmitted through fungal hyphal anastomosis or spores.
• Previously, Sclerotinia sclerotiorum hypovirulence-associated DNA virus 1 (SsHADV-1) was shown to infect its fungal host extracellularly.
• The transmission routes and ecological role of many mycoviruses remain incompletely understood.

Purpose of the Study:

• To investigate the potential of insects as vectors for SsHADV-1 transmission.
• To determine if SsHADV-1 can replicate within insect hosts.
• To explore the ecological implications of insect-mediated SsHADV-1 transmission for fungal disease management.

Main Methods:

• Infection of the mycophagous insect Lycoriella ingenua with SsHADV-1 through feeding on infected Sclerotinia sclerotiorum.
• Detection and quantification of SsHADV-1 in various insect life stages (larvae, pupae, adults, eggs) and inoculated insect cells (Spodoptera frugiperda) using RT-PCR, Northern blot, immunofluorescence, and flow cytometry.
• Observation of virus transmission dynamics between fungus, insect, and host plants (rapeseed) in laboratory and field settings.
• Analysis of insect behavior and volatile organic compounds in response to virus-infected fungal isolates.

Main Results:

• Lycoriella ingenua larvae acquired, replicated, and retained SsHADV-1 after feeding on infected S. sclerotiorum.
• The virus was successfully transmitted to insect offspring via eggs, indicating vertical transmission.
• Inoculation experiments confirmed SsHADV-1 replication in insect cells.
• Infected fungal isolates produced fewer repellent volatile substances, attracting more L. ingenua adults.
• SsHADV-1 was detected in L. ingenua collected from rapeseed fields, confirming natural transmission.

Conclusions:

• The mycophagous insect Lycoriella ingenua serves as an effective vector for SsHADV-1, facilitating its transmission between fungal hosts and plants.
• SsHADV-1 can replicate within insect cells and be transmitted both horizontally (fungus-to-insect, insect-to-plant) and vertically (insect-to-offspring).
• The findings provide a foundation for developing novel biocontrol strategies against fungal diseases using insect-vectored mycoviruses.
• This research expands our understanding of SsHADV-1 ecology and the broader ecological significance of emerging SsHADV-1-like viruses found in diverse environments.