Laccase2 is required for cuticular pigmentation in stinkbugs

During the maturation of insect cuticle, protein-protein and protein-chitin crosslinkages are formed by the action of diphenoloxidases. Two types of diphenoloxidases, laccases and tyrosinases, are present in the insect cuticle. In coleopteran and hymenopteran insects, laccase2 gene has been identified as encoding an enzyme principally responsible for cuticular pigmentation and hardening, whereas biological roles of laccase genes in hemimetabolous insects remain to be established. Here we identified laccase2 genes from three hemipteran stinkbugs, Riptortus pedestris (Alydidae), Nysius plebeius (Lygaeidae) and Megacopta punctatissima (Plataspidae). In R. pedestris, laccase2 gene was highly expressed in epidermal tissues prior to molting. When the gene expression was suppressed by an RNA interference technique, cuticular pigmentation after molting were blocked depending on the dose of injected double-stranded RNA targeting the laccase2 gene. Similar results were obtained for N. plebeius and M. punctatissima. In all the stinkbug species, injecting 20 ng of double-stranded RNA was sufficient to prevent the cuticular maturation. These results indicate that laccase2 gene is generally required for cuticular pigmentation in different stinkbug families, highlighting its conserved biological function across diverse insect taxa.

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► Laccase2 genes were identified from three stinkbug species of different families.
► RNAi of the laccase2 genes consistently blocked their cuticular maturation.
► The laccase2 function is conserved across holometabolous and hemimetabolous insects.