Conserved genomic loci with contrasting transposable element landscapes reveal divergent evolution of tandem P450 clusters in noctuid moths
Description
Gene duplication and transposable element (TE) dynamics contribute to genomic innovation, yet their roles in metabolic adaptation of polyphagous insect pests remain poorly understood. Here, we performed a comparative genomic analysis of cytochrome P450 genes across 12 lepidopteran species, including eight noctuid moths and four representative non-noctuid species, to investigate the evolutionary basis of P450 diversification. We identified a lineage-specific expansion of P450 genes in noctuid moths, particularly within the CYP3 and CYP4 clans. These expansions were concentrated within two conserved genomic regions (Locus 1 and Locus 2) that formed large tandem arrays. Comparative analysis of TE landscapes revealed distinct genomic environments between these loci. Locus 1 showed significantly higher TE enrichment in noctuids and diverse TE compositions, whereas Locus 2 contained extensive P450 arrays despite relatively lower TE abundance. However, TE enrichment was not strongly associated with P450 copy number variation, suggesting that TE accumulation represents a locus-specific genomic feature rather than a universal driver of P450 expansion. Evolutionary analyses detected episodic diversifying selection in both loci, indicating heterogeneous selective pressures following gene duplication. Transcriptomic analysis of Spodoptera frugiperda under insecticide stress further revealed contrasting regulatory patterns: Locus 2 paralogs exhibited coordinated expression responses, whereas Locus 1 paralogs displayed greater expression variation. Together, our findings demonstrate that conserved genomic hotspots with distinct structural and regulatory properties have contributed to the repeated expansion and diversification of P450 clusters in noctuid moths.