Specialisation and gene expression of Ostrinia scapulalis (ABB) and O. nubilalis (ECB). Ostrinia

This study analysed phenotypic and transcriptomic responses of two Ostrinia species, O. scapulalis (ABB) and O. nublilalis (ECB), in order to identify candidate genes involved in host specialization at the larval stage. For this purpose, we sampled ECB and ABB diapausing larvae in 2013 near Versailles in France (48°48'19N, 2°08'06 E) from maize and mugwort stems respectively. ECB and ABB Larval performances were observed by setting up a reciprocal transplant experiment in which mugwort and maize plants were infested with eggs of each Ostrinia species. After their development on, and in, plants, fourth-instar larvae (l4) were collected for each of the four experimental set-ups (ABBmugwort, ABBmaize, ECBmugwort, ECBmaize). Each set-up was repeated three times. In total, 12 RNAseq libraries were constructed, 6 for each Ostrinia species. After Illumina HiSeq sequencing and bioinformatics cleaning and post-processing, a transcriptome was assembled for each species, ECB and ABB, using the program Trinity. Subsequently, applying EMBOSS-splitter and Newbler, we generated for each species a hybrid transcript set by combining the corresponding de novo transcriptome with previously published 454 transcriptomes (Gschloessl et al. 2013). This way, two reference transcriptomes were established, one for ECB, the other for ABB. Last, DE (differentially expressed) genes were detected between experimental set-up and species.