关键词: 斜纹夜蛾, 变态发育, 蜕皮激素, 寄主植物, 基因表达, miRNA

Abstract: 【Aim】 This study aims to explore the expression profiles of CYP450 genes involved in the ecdysone synthesis pathway, so as to provide potential targets for the control of pest insects. 【Methods】The CYP450 genes were identified from the genome of Spodoptera litura by homologous blast using the Bombyx mori CYP450 genes as queries, and their phylogenetic tree was constructed. qPCR was carried out to examine the expression levels of the identified CYP450 genes in different developmental stages (6th instar larva, prepupa and pupa), various tissues (midgut, cuticle and fat body) of these three developmental stages, and the midgut of the 5th instar larvae after the 4th instar larvae fed with the leaves of different host plants ［pepper (Capsicum annuum), cucumber (Cucumis sativus), sweet potato (Ipomoea batatas) and peanut (Arachis hypogaea)］. The developmental duration from the 4th instar larva to pupa was recorded after the 4th instar larvae were fed with the leaves of different host plants. In addition, microRNAs (miRNAs) targeting the identified CYP450 genes were predicted using four programs, PITA, miRanda, microTar and RNAhybrid. 【Results】 Six CYP450 orthologs, CYP307A1, CYP306A1, CYP302A1, CYP315A1, CYP314A1 and CYP18A1, involved in the ecdysone synthesis pathway were identified in S. litura, and the phylogenetic tree showed that the six genes belong to two clans, CYP2 and mitochondrial CYP, respectively. CYP306A1, CYP314A1 and CYP18A1 showed the highest expression levels in the 6th instar larvae, prepupae and pupae, respectively, and the highest expression levels in the midgut of the 6th instar larvae, the fat body of prepupae and the cuticle of pupae, respectively. After the 4th instar larvae of S. litura were fed with the leaves of sweet potato and peanut, the developmental duration from the 4th instar larva to pupa was significantly prolonged, and the expression level of CYP306A1 in the midgut of the 5th instar larvae was significantly upregulated, as compared to those fed with the artificial diet. Multiple miRNA binding sites were identified on CYP307A1, CYP315A1, CYP314A1 and CYP18A1. 【Conclusion】 CYP306A1, CYP314A1 and CYP18A1 in the ecdysone synthesis pathway play key regulatory roles in the larva, prepupa and pupa of S. litura, respectively, and are also involved in detoxification of the secondary metabolites in host plants and subject to the control of various miRNAs. These findings not only help to understand the complex mechanism of insect metamorphosis, but also provide potential targets for pest insect control, which will benefit for the sustainable management of pest insects including S. litura.

Key words: Spodoptera litura, metamorphosis, ecdysone, host plant, gene expression, miRNA