Constraints on the evolution of chromosome dosage compensation: a test in butterflies and moths
Project Award Date: 02-15-2015
The research proposed here pursues a definitive, phylogenetically informed assessment of sex chromosome dosage compensation in Lepidoptera (moths and butterflies). Dosage compensation equalizes between sexes the gene expression on the sex chromosome. Without it, the sex chromosome of the heterogametic sex would be under-expressed relative to the homogametic sex due to unequal gene copy number between sexes. Theory suggests dosage compensation is an essential part of sex chromosome differentiation but recent results indicate it might be universally absent from female-heterogametic species. The status of dosage compensation is currently unresolved in Lepidoptera, a prominent female-heterogametic taxon, and preliminary results suggest some lepidopteran species exhibit a novel form of dosage compensation. We will combine transcriptome and genome sequencing to characterize patterns of dosage compensation in 10 phylogenetically diverse lepidopteran species. We will use comparative genomic analyses and resequencing of targeted species to infer patterns of male mutation bias and the relative effective population sizes of autosomes and sex chromosomes, comparing between species these population genetic factors thought to correlate with the presence of dosage compensation. Particular effort will be made to construct a high-quality genome assembly of the tortricid moth, Cydia pomonella.
This moth family harbors neo-sex chromosomes originating from a fusion of an autosome with an ancestral sex chromosome; this neo-sex system provides a novel opportunity to examine the evolution of dosage compensation and sex chromosomes in a tractable female-heterogametic taxon.