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Endogenous viral elements and PIWI gene evolution in Spodoptera: diversity, conservation, and piRNA production
Salvador Herrero1, Lino Ometto2, Javier López-Rius1
1Universitary Institute BIOTECMED, University of Valencia, Burjassot, Spain.
Insect Biochemistry and Molecular Biology
|June 10, 2026
Summary
Endogenous viral elements (EVEs) in Spodoptera moths, particularly non-retro-transcribing RNA virus (nrEVEs), can act as genomic fossils or contribute to antiviral immunity through piRNA production. This study reveals their diversity and potential immune function in these agricultural pests.
Area of Science:
- Genomics
- Virology
- Insect Biology
Background:
- Endogenous viral elements (EVEs) are integrated viral sequences in host genomes, acting as molecular fossils.
- Some non-retro-transcribing RNA virus EVEs (nrEVEs) in arthropods generate PIWI-interacting RNAs (piRNAs) and function as immune effectors.
- Spodoptera species are significant agricultural pests, making their interactions with viruses relevant for pest control.
Purpose of the Study:
- To investigate the diversity and function of nrEVEs in four Spodoptera moth species.
- To understand the evolutionary history and genomic distribution of nrEVEs in Lepidoptera.
- To explore the potential antiviral roles of nrEVE-derived piRNAs in Spodoptera.
Main Methods:
- Comparative genomics to identify and characterize nrEVEs across Spodoptera species.
- Small RNA sequencing to detect piRNA production from nrEVEs.
- Bioinformatic analyses to assess piRNA complementarity to viral genomes and study PIWI Argonaute gene evolution.
Main Results:
- Identified 21-27 nrEVEs per genome in Spodoptera, with enrichment on the Z chromosome, primarily from (-)ssRNA viruses.
- Discovered conserved and species-specific nrEVE integrations, with one dating back approximately 15 million years.
- Observed that only a subset of nrEVEs produced piRNAs, mainly in ovarian tissues, with evidence of antiviral activity in Spodoptera frugiperda against Spodoptera frugiperda rhabdovirus (SfRV).
- Detected lineage-specific expansions and positive selection in Spodoptera PIWI Argonaute genes.
Conclusions:
- nrEVEs in Spodoptera moths likely have a dual role: persisting as genomic fossils and potentially providing antiviral defense via piRNA production.
- The findings contribute to understanding insect-virus coevolution and the functional significance of EVEs in noctuid moths.
- Spodoptera's PIWI Argonaute gene evolution suggests a unique trajectory in antiviral defense mechanisms.
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