Transcriptional response of females in Ostrinia spp. during the oviposition period. 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 preference of adult females.We sampled diapausing ECB larvae from maize and ABB larvae from mugwort near Versailles (48°48019″N, 2°08006″E) in February 2013. After one complete life cycle in laboratory conditions, we released 20 virgin females and 15 virgin males in different experimental set-ups in semi-natural conditions:(1)”choice” cages, with maize and mugwort plants(2)”maize” cages (usual host for ECB) and(3) “mugwort” cages (usual host for ABB).After three nights, the number and locations of egg-masses laid by released females were recorded and the recovered females were flash-frozen in nitrogen liquid before their storing at -80°C until RNA extraction.After sequencing, the reads of the 12 ECB RNAseq libraries were assembled with the Trinity program on one side and the 12 ABB libraries on the other side.Subsequently, applying EMBOSS-splitter and Newbler, we generated for each species a hybrid transcript set by combining the corresponding de novo HiSeq transcriptome with the species-specific 454 transcriptome previously obtained by Gschloessl et al. (2013) from 4 ECB adults and 4 ABB, respectively.We observed strong differences in the adult behavior between ECB and ABB, in particular for the host plant choice by females during the egg laying. Indeed, we observed in ECB and ABB gravid females a strong preference for their respective native host plant (maize for ECB; mugwort for ABB). In addition, the ECB females exhibited an avoidance of mugwort (alternative and putative ancestral host plant) in no choice conditions.To target the genes potentially involved in fertility and oviposition choice, we realized a gene expression analysis of ECB and ABB female adult moths during the mating and oviposition steps through an RNAseq approach.