Locust cGAS-like Receptors Recognize Derivatives of a Gypsy Retrotransposon to Synergize with RNAi Against Viral Invasion

Transposable elements (TEs) are increasingly recognized as modulators of innate immunity, yet their antiviral functions remain poorly understood outside mammals and dipterans. Here, we identify a long terminal repeat retrotransposon, LmGypsy, as a key regulator of antiviral defense in Locusta migratoria. The infection of Acrididae reovirus (ARV) induces rapid upregulation of LmGypsy, and its inhibition compromises antiviral resistance. Mechanistically, LmGypsy promotes viral-derived DNA (vDNA) production, which drives Dicer-2-dependent biogenesis of virus-derived small interfering RNAs (vsiRNAs) to enhance RNA interference-mediated viral clearance. Notably, vDNA persists throughout infection, suggesting a role in sustaining antiviral responses. In parallel, LmGypsy activity is positively associated with induction of cyclic GMP-AMP synthase (cGAS)-like receptors (LmcGAS1/2/4) and their downstream effector Stimulator of Interferon Genes (STING). Together, these findings support a dual-layer antiviral strategy and indicate that TE-mediated immunity represents a widespread antiviral mechanism across taxa.