Non-Coding Transcripts From Diversified Members of IgLec Family Protect Antiviral Effectors From Viral miRNA

Immune gene families frequently produce numerous non-coding transcripts, yet their biological functions remain largely unexplored. Here, using the arthropod immunoglobulin domain-containing lectin (IgLec) family as a paradigm, we provide evidence that this complexity may reflect a critical defensive function for non-coding transcripts in antiviral immunity. IgLec is restricted to decapod infraorders (Brachyura and Astacidea), and a structurally related bacterial homolog suggests its origin may involve horizontal gene transfer. The IgLec family generates extraordinary transcript diversity through three mechanisms, multi-locus duplication, inter-locus recombination, and extensive alternative splicing, yielding both protein-coding and non-coding transcripts. Protein-coding IgLec variants restrict viral replication by inducing antimicrobial peptide expression. Upon white spot syndrome virus infection, non-coding transcripts (e.g., intron-retaining transcripts) are preferentially targeted by virus-encoded microRNA-N48, thereby protecting protein-coding isoforms from repression. Loss of these decoy transcripts compromises antiviral defense and increases host mortality. Collectively, these results reveal a decoy-based antiviral strategy in which non-coding transcripts safeguard immune effectors from pathogen subversion, uncovering an unrecognized layer of innate immunity.