Identification of chemosensory genes expressed in legs of nymphalid butterflies

Chemoreception plays a major role in host plant selection by insects. However, genes underlying host selection and host specificity of insects are largely unexplored. To identify the genetic basis of host plant selection, we performed RNA sequencing using four butterfly species of the tribe Nymphalini (Vanessa cardui, Vanessa indica, Polygonia c-aureum, and Araschnia burejana). For each species, three female individuals that were siblings were selected for the experiment. All legs were dissected within two days after eclosion, and used for RNA extraction. RNA sample for each individuals was treated separately. cDNA libraries for HiSeq platform were constructed from those RNA samples. One out of three samples per species was also used for making a cDNA library for MiSeq platform. Subsequently, these cDNA libraries were sequenced using HiSeq2500 and MiSeq. After quality filtering, RNA-seq reads for each species were assembled together with Trinity. Chemosensory genes included in these de novo assemblies were detected based on BLAST searches.