Investigating the role of a kinesin gene in butterfly mimicry

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Mimicry among butterfly species is a classic example of evolution and adaptation. The brightly coloured neotropical Heliconius butterflies are one of the best studied examples, but the molecular genetic basis of mimicry remains poorly understood. In particular mimicry offers an opportunity to study the repeatability of evolution, as the same patterns emerge again and again in divergent lineages. The project falls into two broad areas, first we use cutting edge sequencing technology to make a genetic map of the H. melpomene genome. This will be used to help assemble the genome sequence currently being generated. This will form the basis for a genome-wide survey of adaptive divergence between H. melpomene races. Divergent geographic populations of this species form narrow hybrid zones where they hybridise and exchange genes. Thus, narrow regions of the genome controlling wing patterns are genetically differentiated against a background of extensive recombination. This offers a powerful opportunity to identify changes responsible for wing pattern differentiation. We will first characterise variation within and between races by genome resequencing at low coverage. Then we will use novel 'sequence capture' technology to enrich genomic DNA for regions of interest from 96 individuals, taken from six phenotypic races of H. melpomene. The experiment will be designed to sample two chromosomal regions containing wing patterning genes, and a further 12,000 variable sites located across the genome. This will offer a unique genome-wide analysis of parallel divergence between the six populations sampled. In particular we aim to determine a) how much of the genome is involved in colour pattern divergence b) whether the same regions are implicated across independent hybrid zones c) estimate the age of the alleles involved in wing pattern divergence and d) identify putative functional sites for further analysis. The second major aim of the project is to investigate the kinesin gene that represents a strong candidate locus for controlling the red forewing band of H. melpomene. We will study the spatial distribution of kinesin gene expression patterns between divergent phenotypes, in order to test whether spatial regulation underlies pattern regulation. Many genes show different variants generated by alternative splicing, generating variant forms of the protein containing alternative forms of the exons. Alternative splicing is a potentially powerful but under-explored mechanism that could generate evolutionarily relevant variation. We have evidence for alternative splicing the Kinesin gene, and here will characterise the isoforms of this gene and test for correlations between isoform expression and wing phenotype. We will investigate the molecular function of the gene, including a search for other molecules that interact with the kinesin protein, and test to confirm its motor function. Finally, we will develop trangenics methods for explicitly testing the function of the kinesin gene in wing pattern specification in divergent races of H. melpomene. The major gene dominant control of the red band means that we expect to be able to generate a red-banded phenotype by expressing the 'red' kinesin allele in a yellow banded phenotype. This will provide the first explicit test of function for a gene causing pattern variation in any butterfly.