Transcriptomic response to host and non-host plants during oviposition in two closely related moth species

We present here a comprehensive analysis of the transcriptomic response to plant environments in ovipositing females of two sibling species of phytophagous moths affiliated to different host ranges: the European corn borer (ECB) and the adzuki bean borer (ABB). We first assembled and annotated a de novo reference transcriptome based on a high throughput RNA sequencing of females placed in different plant environments, then we measured differences in gene expression between ECB and ABB, and also within each moth species between environments. We further related the differentially expressed (DE) genes to the host preference in ECB and ABB and highlighted the functional categories involved. More specifically, we conducted an analysis on chemosensory genes previously characterized in ECB, ABB and other related Ostrinia species, as these genes are considered as good candidates for the host recognition before oviposition. Overall, we recorded more DE genes in ECB than in ABB samples, what could highlight the higher strength of the host specialization in ECB compared to ABB as observed at the behavioral level. We also noticed that the genes involved in the preference for their respective host were different between ECB and ABB. At the functional level, the response to plant environment in ECB and ABB during oviposition involved many processes, including the chemosensory repertoire as expected, but also metabolism of carbohydrates, lipids, proteins, and amino acids, detoxification mechanisms and immunity. Together, our results allowed identifying genes and functions candidates for specialization and also for the species divergence between ECB and ABB. By ad-hoc categorization, we discriminated some genes responding to the environment with similar or divergent pattern in ECB and ABB. Among them, we highlighted new lines of research like carbohydrates metabolism or virus and retrovirus dynamics.