Characterization of a hotspot for mimicry: assembly of a butterfly wing transcriptome to genomic sequence at the HmYb/Sb locus

Authors


  • The authors have a broad interest in the genetic basis of evolutionary adaptation. Laura Ferguson, Siu Fai Lee, Nicola Nadeau and Simon Baxter, Nicola Chamberlain, Richard ffrench-Constant and Chris Jiggins are specifically working on the genetics of wing patterning in Heliconius butterflies. The work was carried out as part of Laura’s PhD, and the other group members were postdoctoral researchers. Mathieu Joron is a senior researcher in Paris focusing on the genetics of the polymorphic Heliconius species, H. numata. Paul Wilkinson, Alexie Papanicolaou, Sujai Kumar and Thuan-Jin Kee are interested in developing bioinformatic tools for analysis of evolutionary problems. Richard Clark, Claire Davidson, Rebecca Glithero and Helen Beasley are interested in genomic sequencing and analysis. Heiko Vogel is an expert in preparation of transcriptome libraries, and has a general interest in the genetic aspects of chemical ecology.

Chris Jiggins, Fax: 01223 336676; E-mail: cj107@cam.ac.uk

Abstract

The mimetic wing patterns of Heliconius butterflies are an excellent example of both adaptive radiation and convergent evolution. Alleles at the HmYb and HmSb loci control the presence/absence of hindwing bar and hindwing margin phenotypes respectively between divergent races of Heliconius melpomene, and also between sister species. Here, we used fine-scale linkage mapping to identify and sequence a BAC tilepath across the HmYb/Sb loci. We also generated transcriptome sequence data for two wing pattern forms of H. melpomene that differed in HmYb/Sb alleles using 454 sequencing technology. Custom scripts were used to process the sequence traces and generate transcriptome assemblies. Genomic sequence for the HmYb/Sb candidate region was annotated both using the MAKER pipeline and manually using transcriptome sequence reads. In total, 28 genes were identified in the HmYb/Sb candidate region, six of which have alternative splice forms. None of these are orthologues of genes previously identified as being expressed in butterfly wing pattern development, implying previously undescribed molecular mechanisms of pattern determination on Heliconius wings. The use of next-generation sequencing has therefore facilitated DNA annotation of a poorly characterized genome, and generated hypotheses regarding the identity of wing pattern at the HmYb/Sb loci.

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