Chemosensory gene signatures of ecological niche and behavioural specialisation in Sirex noctilio

Abstract

Background The evolutionary and ecological success of insects may in part be due to their sophisticated and highly evolved chemosensation systems. Insect chemosensation genes form some of the largest multigene families known and are important targets for reverse genetics approaches to study the relationship between ecology, evolution and genomics. Here we use genomics, phylogenetics, transcriptomics and differential expression analyses to investigate the chemosensory gene repertoire of Sirex noctilio, one of the most economically important pests of Pinus plantations in many parts of the world. Results A total of 129 chemosensation genes, including 45 ORs, 12 GRs, 48 IRs, 1 SNMP, 14 OBPs and 9 CSPs, were identified and phylogenetically characterised in the genome of S. noctilio. RNA-sequencing of olfactory and non-olfactory adult and pupa S. noctilio tissues enabled expression profiling of the identified chemosensation genes. The identified antennae-, ovipositor- and leg-biased chemosensation genes are of particular interest due to their potential olfactory and oviposition function, and the sexual dimorphism of these tissues. Conclusions Tissue- and sex-biased chemosensation gene expression were observed throughout the 15 tissue transcriptomes investigated. This study broadens our understanding of the peri-receptive events of S. noctilio chemosensation and strengthens the foundation for chemical ecology studies and functional deorphanisation of S. noctilio chemosensation genes. The phylogenetically basal position of this woodwasp within the Hymenoptera also informs the evolution of the multigene families associated with chemosensation in this ecologically and economically important order.