Evolution of bric-a-brac regulation in Drosphilinae

University Of Wisconsin-Madison, Madison WI

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Abstract

The field of evolutionary biology has long been interested in the molecular basis of morphological evolution; however a clear understandingremains elusive. Abdominal pigmentation in the subgroup Drosophilinae is a well studiedtrait suitable for studies to identify the genetic changes culminating in the emergence of similar and diversepigmentation patterns. In addition to diverse pigmentation patternsit is apparent, based on phylogeny, that similar patternsof pigmentation haveappeared independently. In the melanogaster speciesgroup sexually dimorphic, segmentspecific pigmentation has recently evolved. The terminal abdominal segmentsof males are dark, whereas all segmentsare lightly pigmentedin females. Closely related groups of species are monomorphic, i.e. all segments are lightly pigmented in both sexes. In all species, pigmentation is prevented where the gene products of bric-a-brac (bab), a represserof pigmentation, are expressed. In dimorphic species, a newly evolved circuitry involving homeotic and sex-determination inputs repressesbab expression in the terminal segments of the male, but not the female. This proposal will analyze how Drosophila melanogaster bab gene regulatory elements has evolvedto integrate responsiveness to homeotic and sex-determination inputs and the extent that both similar and diverse abdominal pigmentation patterns haveevolved through the modification of orthologous bab sequences. Insight from the mechanisms of enhancer evolution and function in Drosophilinae will very likely apply to the understandingof cis-regulatoryelements in vertebrates as similar sequence alterationshave significant medical implications inhumans.