Cytochrome P450 diversification and hostplant utilization patterns in specialist and generalist moths: Birth, death and adaptation

Abstract

Across insect genomes, the size of the cytochrome P450 monooxygenase ( CYP ) gene superfamily varies widely. CYP ome size variation has been attributed to reciprocal adaptive radiations in insect detoxification genes in response to plant biosynthetic gene radiations driven by co‐evolution between herbivores and their chemically defended hostplants. Alternatively, variation in CYP ome size may be due to random “birth‐and‐death” processes, whereby exponential increase via gene duplications is limited by random decay via gene death or transition via divergence. We examined CYP ome diversification in the genomes of seven Lepidoptera species varying in host breadth from monophagous ( Bombyx mori ) to highly polyphagous ( Amyelois transitella ). CYP ome size largely reflects the size of Clan 3, the clan associated with xenobiotic detoxification, and to some extent phylogenetic age. Consistently across genomes, families CYP 6, CYP 9 and CYP 321 are most diverse and CYP 6 AB , CYP 6 AE , CYP 6B, CYP 9A and CYP 9G are most diverse among subfamilies. Higher gene number in subfamilies is due to duplications occurring primarily after speciation and specialization (“P450 blooms”), and the genes are arranged in clusters, indicative of active duplicating loci. In the parsnip webworm, Depressaria pastinacella , gene expression levels in large subfamilies are high relative to smaller subfamilies. Functional and phylogenetic data suggest a correlation between highly dynamic loci (reflective of extensive gene duplication, functionalization and in some cases loss) and the ability of enzymes encoded by these genes to metabolize hostplant defences, consistent with an adaptive, nonrandom process driven by ecological interactions.

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