Global Transcriptome Sequencing Reveals Molecular Profiles of Summer Diapause Induction Stage of Onion Maggot, Delia antiqua (Diptera: Anthomyiidae)

The onion maggot, Delia antiqua, is a worldwide subterranean pest and can enter diapause during summer and winter seasons. The molecular regulation of the ontogenesis transition remains largely unknown. Here we used high-throughput RNA-Seq to identify candidate genes and processes linked to summer diapause induction by comparing the transcriptome differences between the most sensitive larval developmental stage of summer-diapause (SD) and non-diapause (ND). Nine pair-wise comparisons were performed and significantly differentially regulated transcripts were identified. Several functional terms related to lipid, carbohydrate and energy metabolism, environmental adaption, immune response and aging were enriched during the most sensitive SD induction period. A subset of genes, including circadian clock genes was expressed differentially under diapause induction conditions, and there was much more variation in the most sensitive period of ND than SD-destined larvae. These expression variations probably resulted in a deep restructuring of metabolic pathways. Potential regulatory elements of summer diapause induction including genes related to lipid, carbohydrate, energy metabolism and environmental adaption. Collectively, our results suggest circadian clock is one of the key drivers for integrating environmental signals into the SD induction. Our transcriptome analysis provides insight into the fundamental role the circadian clock plays in summer diapause induction in this important model insect species, and contributes to the in-depth elucidation of the molecular regulating mechanism of insect diapause induction.

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