Antheraea pernyi is one of the most famous edible and silk-producing wild silkworms of Saturniidae. Structural cuticular proteins (CPs) are the primary component of insect cuticle. In this paper, the CPs in the genome of A. pernyi were identified and compared with those of the lepidopteran model species Bombyx mori, and expression patterns were analyzed based on the transcriptomic data from the larval epidermis/integument (epidermis in the following) and some non-epidermis tissues/organs of two silkworm species. A total of 217 CPs was identified in the A. pernyi genome, a comparable number to B. mori (236 CPs), with CPLCP and CPG families being the main contribution to the number difference between two silkworm species. We found more RR-2 genes expressed in the larval epidermis of fifth instar of A. pernyi than B. mori, but less RR-2 genes expressed in the prothoracic gland of A. pernyi than B. mori, which suggests that the hardness difference in the larval epidermis and prothoracic gland between the two species may be caused by the number of RR-2 genes expressed. We also revealed that, in B. mori, the number of CP genes expressed in the corpus allatum and prothoracic gland of fifth instar was higher than that in the larval epidermis. Our work provided an overall framework for functional research into the CP genes of Saturniidae.

For a half-century, the commercial wild silkworm, Antheraea pernyi, has been protected by coumaphos, which is an internal organophosphorus insecticide used to kill the potential parasitic fly larvae inside. Knowledge about the detoxification genes of A. pernyi as well as the detoxification mechanism for this species remains severely limited. In this study, we identified 281 detoxification genes (32 GSTs, 48 ABCs, 104 CYPs, and 97 COEs) in the genome of this insect, which are unevenly distributed over 46 chromosomes. When compared to the domesticated silkworm, Bombyx mori, a lepidopteran model species, A. pernyi has a similar number of ABCs, but a greater number of GSTs, CYPs, and COEs. By transcriptome-based expression analysis, we found that coumaphos at a safe concentration level significantly changed the pathways related to ATPase complex function and the transporter complex in A. pernyi. KEGG functional enrichment analysis indicated that protein processing in the endoplasmic reticulum was the most affected pathway after coumaphos treatment. Finally, we identified four significantly up-regulated detoxification genes (ABCB1, ABCB3, ABCG11, and ae43) and one significantly down-regulated detoxification gene (CYP6AE9) in response to coumaphos treatment, suggesting that these five genes may contribute to detoxification of coumaphos in A. pernyi. Our study provides the first set of detoxification genes for wild silkworms from Saturniidae and highlights the importance of detoxification gene repertoire in insect pesticide tolerance.

Diapause hormone (DH) is an important endocrine substance capable of influencing diapause in Lepidoptera moths that is encoded by the neuropeptide hormone DH-PBAN gene. Imidazole derivative KK-42 is a synthetic insect growth regulator that can affect diapause in Lepidoptera moths, and appears to have an opposite physiological function to DH. To test the hypothesis that KK-42 may be operating through DH to affect diapause, here, we used two Lepidoptera species Bombyx mori L. and Antheraea pernyi that enter egg and pupal diapause, respectively, through examining whether KK-42 can influence DH-PBAN and some associated mRNA expression. We found that the protein sequences of DH-PBAN in insects were highly variable, although the PRXamide C-terminus was conserved. We also found that KK-42 induced significant up-regulation and prolonged expression duration of DH-PBAN in both A. pernyi and B. mori pupae, as well as in trimolter larvae of B. mori that were induced by the application of KK-42 from the normal tetramolter larvae. In addition, KK-42 can significantly upregulate glutamic acid decarboxylase (GAD) expression in B. mori in transcriptome data. Our findings suggested that KK-42 influences diapause by upregulating GAD expression, promoting DH accumulation to prolong the secretion time of DH-PBAN.