title: Is function of the Drosophila homeotic gene Ultrabithorax canalized?
abstract: Genetic variation affecting the expressivity of an amorphic allele of the homeotic gene Ultrabithorax, (Ubx1) was characterized after 11 generations of introgression into 29 different isofemale lines. Heterozygotes display a range of haploinsufficient phenotypes, from overlap with wild-type halteres to dramatic transformations such as a 50% increase in area and the presence of over 20 bristles on the anterior margin of each haltere. In both the wild-type and mutant genetic backgrounds, there is moderate genetic variance and low environmental variance/developmental asymmetry, as expected of a trait under stabilizing selection pressure. Surprisingly, there is little evidence that mutant halteres are more variable than wild-type ones, so it is unclear that haltere development is also canalized. The correlation between wild-type and Ubx haltere size is very low, indicating that interactions among modifiers of Ubx are complex, and in some cases sex-specific. The potential quantitative genetic contributions of homeotic genes to appendage morphology are discussed, noting that population-level effects of variation in key regulatory genes may be prevalent and complex but cannot be readily extrapolated to macroevolutionary diversification.
authors.affiliation: Department of Biology, The University of Michigan, Ann Arbor 48109-1048, USA. ggibson@umich.edu
authors.forename: G
authors.initials: G
authors.lastname: Gibson
authors.forename: S
authors.initials: S
authors.lastname: van Helden
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000235:genetics*; D005260:Female; D005801:Genes, Homeobox; D017344:Genes, Insect; D014644:Genetic Variation; D018398:Homeodomain Proteins / Q000235:genetics*; D008297:Male; D014157:Transcription Factors
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D014157:Transcription Factors; C066177:Ubx protein, Drosophila