Comparative analysis of Nymphalidae gene expression on different host plants
Transcriptome studies of insect herbivory are still rare, yet studies in model systems have uncovered patterns of transcript regulation that appear to provide insights into how insect herbivores attain polyphagy, such as a general increase in expression breadth and regulation of ribosomal proteins. We investigated the potential generality of these emerging patterns, in the Swedish comma, Polygonia c-album, which is a polyphagous, widely-distributed butterfly.  Urtica dioica and Ribes uva-crispa are hosts of P. c-album, but Ribes represents a recent evolutionary shift onto a very divergent host. Utilizing the assembled transcriptome for read mapping, we assessed gene expression finding that life-history (i.e. 2nd vs. 4th-instar regulation) had a limited influence on gene expression plasticity. In contrast, differential expression in response to host-plant identified genes encoding serine-type endopeptidases, membrane-associated proteins and transporters. The differential regulation of ribosomal proteins and genes involved in nucleic acid binding suggests that polyphagy involves large scale transcriptional changes, rather than simple modifications of detoxification enzymes. Our results indicate that emerging patterns of transcript regulation from model species appear relevant in species when placed in an evolutionary context.