Transcriptome Analysis Reveals Candidate Genes During the Prepupal-pupal Transition in the Oriental Armyworm, Mythimna separata (Walker) (Lepidoptera: Noctuidae)

Abstract Background Metamorphosis ensures the transformation of a larva of the holometabolous insects into a reproductive adult through a transitory pupal stage. Understanding how changes in expression levels of genes during the prepupal-pupal transition will inform us of how the metamorphosis arises. Results In this study, mature larvae (ML), wandering (W), 1 day (P1), 5 days (P5), and 10 days (P10) after pupation of the Mythimna separata (Walker), a notorious migratory pest of agricultural crops, were selected, forming five groups. RNA-Seq revealed that the draft transcriptome assembly contained 140562 contigs, and more than half (74,059) were similar to sequence at NCBI (e value < e− 3), including 22884, 23534, 26643, and 33238 differentially expressed genes (DEGs) in ML vs W, W vs P1, P1 vs P5, and P5-vs-P10, respectively. Comparative transcriptomics revealed the enrichment of biological processes related to the membrane and integral component of membrane, which includes the cuticular protein (CP), 20-hydroxyecdysone (20E), and juvenile hormone (JH) biosynthesis, enabled us to delineate and partially validate the metabolic pathway in M. separata. Of these DEGs, 33 CP, 18 20E, and 7 JH genes were differentially expressed across the developmental stages. Correlation analysis uncovered that the relative expression levels of 10 selected CP, 20E, and JH-related genes obtained by real-time PCR quantitative (RT-qPCR) matched well with their FPKM values derived from RNA-seq. Conclusions The data gave here represent an important first step to uncover the molecular mechanism of metamorphosis in M. separata, which also provide valuable information for manipulation of insect development and metamorphosis using the obtained DEGs as targets and broaden the applications of available tools for insect pest control.