Transcriptomic analysis of differentially expressed genes in the oriental armyworm Mythimna separata Walker at different temperatures.

The oriental armyworm Mythimna separata Walker is a serious migratory and polyphagous pest that damages major crops and some pastures from the family Gramineae. Temperature is a crucial abiotic factor that affects its survival, development and reproduction, but the thermal responses of this moth at the molecular level are largely unknown. In this research, we sequenced the transcriptomes of oriental armyworms that were reared at three temperatures (20 °C, 25 °C and 30 °C) using an Illumina high-throughput RNA-sequencing (RNA-seq) method. We obtained 54.0 Gb of clean reads and 113,396 transcripts. From a total of 46,681 unigenes identified, 22,911 were annotated to the non-redundant (NR) database. We identified 333 downregulated and 1588 upregulated genes in 20 °C versus 25 °C, and 1096 downregulated and 875 upregulated genes at 30 °C versus 25 °C by differential expression of genes (DEGs). GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analyses revealed several functional terms related to carbohydrate metabolism, energy metabolism, and xenobiotics metabolism. DEGs involved in glycolysis, the citrate cycle, oxidative phosphorylation, and the composition of myofilaments were significantly downregulated, while most heat shock protein genes (HSPs) and genes in the ubiquitin-mediated proteasome pathway were upregulated at 30 °C. Many cytochrome P450 monooxygenase genes (CYPs) in clan 3 were upregulated at 20 °C, while two genes involved in ecdysteroid biosynthesis, CYP302A1 and CYP315A1, were upregulated at 30 °C. These data may improve the understanding of the complex molecular mechanisms involved in the thermal responses of M. separata.