title: Gene expression underlying adaptive variation in Heliconius wing patterns: non-modular regulation of overlapping cinnabar and vermilion prepatterns.
abstract: Geographical variation in the mimetic wing patterns of the butterfly Heliconius erato is a textbook example of adaptive polymorphism; however, little is known about how this variation is controlled developmentally. Using microarrays and qPCR, we identified and compared expression of candidate genes potentially involved with a red/yellow forewing band polymorphism in H. erato. We found that transcripts encoding the pigment synthesis enzymes cinnabar and vermilion showed pattern- and polymorphism-related expression patterns, respectively. cinnabar expression was associated with the forewing band regardless of pigment colour, providing the first gene expression pattern known to be correlated with a major Heliconius colour pattern. In contrast, vermilion expression changed spatially over time in red-banded butterflies, but was not expressed at detectable levels in yellow-banded butterflies, suggesting that regulation of this gene may be involved with the red/yellow polymorphism. Furthermore, we found that the yellow pigment, 3-hydroxykynurenine, is incorporated into wing scales from the haemolymph rather than being synthesized in situ. We propose that some aspects of Heliconius colour patterns are determined by spatio-temporal overlap of pigment gene transcription prepatterns and speculate that evolutionary changes in vermilion regulation may in part underlie an adaptive colour pattern polymorphism.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA. rreed@uci.edu
authors.forename: Robert D
authors.initials: RD
authors.lastname: Reed
authors.forename: W Owen
authors.initials: WO
authors.lastname: McMillan
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Nagy
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D002080:Butterflies / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D014644:Genetic Variation; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010858:Pigmentation / Q000235:genetics* / Q000502:physiology; D010860:Pigments, Biological / Q000097:blood / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014921:Wings, Animal / Q000254:growth & development / Q000378:metabolism*
chemical_list: D010860:Pigments, Biological