Divergent chemosensory gene expression accompanies ecological specialisation of pea aphid morphs

Abstract

1. Chemosensation is fundamental to the adaptation of insects to their environments. It is used in multiple ecological contexts such as host selection, mate selection, conspecific communication, and predator defence simultaneously. Therefore, understanding the molecular genetic mechanisms underlying specific chemosensory adaptations is important.2. Here a unique study system is used that provides a means to focus on separate aspects of chemosensory specialisation. Pea aphids (Acyrthosiphon pisum) produce different morphs such as winged asexual females, wingless asexual females, sexual females, winged males, and wingless males during their annual life cycle. These morphs have the same or similar genotypes but distinct ecologies and chemosensory repertoires.3. It is hypothesised that divergent chemosensory gene expression underlies ecological and thus chemosensory specialisation. RNA‐Seq data were used to compare chemosensory gene expression levels of five pea aphid morphs. The study focused on 113 genes belonging to six chemosensory gene families (odorant‐binding proteins, chemosensory proteins, odorant receptors, gustatory receptors, ionotropic receptors, and sensory neuron membrane proteins).4. Gene expression analysis revealed that 85% of the chemosensory genes displayed significant differential expression among the five morphs. By performing pairwise morph comparisons, candidate chemosensory genes associated with the distinct chemosensory repertoires of the morphs were identified. Extensive phenotypic plasticity was also found in the expression of chemosensory genes. These results provide insights into the transcriptional variation in chemosensory genes underlying chemosensory and ecological specialisation of distinct morphs.