Differential gene expression according to race and host plant in the pea aphid

Abstract

Host-race formation in phytophagous insects is thought to provide the opportunity for local adaptation and subsequent ecological speciation. Studying gene expression differences amongst host races may help to identify phenotypes under (or resulting from) divergent selection and their genetic, molecular and physiological bases. The pea aphid (Acyrthosiphon pisum) comprises host races specializing on numerous plants in the Fabaceae and provides a unique system for examining the early stages of diversification along a gradient of genetic and associated adaptive divergence. In this study, we examine transcriptome-wide gene expression both in response to environment and across pea aphid races selected to cover the range of genetic divergence reported in this species complex. We identify changes in expression in response to host plant, indicating the importance of gene expression in aphid-plant interactions. Races can be distinguished on the basis of gene expression, and higher numbers of differentially expressed genes are apparent between more divergent races; these expression differences between host races may result from genetic drift and reproductive isolation and possibly divergent selection. Expression differences related to plant adaptation include a subset of chemosensory and salivary genes. Genes showing expression changes in response to host plant do not make up a large portion of between-race expression differences, providing confirmation of previous studies' findings that genes involved in expression differences between diverging populations or species are not necessarily those showing initial plasticity in the face of environmental change.

Gene expression plasticity across hosts of an invasive scale insect species

“…Consequently, there is no effector category in standard gene ontologies, and researchers would not detect enriched differential expression of effectors across hosts using standard enrichment analyses. Furthermore, with one exception [20], the published RNAseq-based differential expression analyses of insect diet variation have studied species with transient connections with their host plants (at least in comparison to sap-sucking insects), and might not be expected to strongly manipulate their host’s induced defenses.…”

Targeted re‐sequencing confirms the importance of chemosensory genes in aphid host race differentiation

“…) and gene expression (Eyres et al . ) has all found indications that chemosensory genes differ between pea aphid races. Although these studies confirm the value of further investigation of chemosensory genes in pea aphids and provide us with a set of potentially interesting target chemosensory genes, this type of broad genomic study is prone to problems of false positives, as well as questionable reliability and repeatability (François et al .…”

Differential expression of chemosensory-protein genes in midguts in response to diet of Spodoptera litura

“…Comparative gene expression studies enable the identification of biological functions involved in the adaptation of organisms to their surrounding environments 15 . By proteomics approach, Celorio-Mancera et al demonstrated the expression of CSP1 changed in response to the caterpillar diet in the mandibular glands.…”

“…One intriguing possibility is that, in midgut, CSPs also could perceive signal chemicals from food resources, thus to mediate feeding behaviors. The analysis of gene expression in response to different treatments have potential to understand the biological function of such genes in adapting surrounding environments 15 and the binding of an external ligand to the CSPs could result in action potentials and contribute to subsequent behaviors 16 . Eventually, studying of CSPs expression variations in response to different plant resources and binding affinities may elucidate the role of CSPs in midgut.…”