| Autor: |
Chakraborty M; Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697.; Department of Biology, Texas A&M University, College Station, TX 77843., Lara AG; Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697., Dang A; Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697., McCulloch KJ; Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697.; Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, MN 55108., Rainbow D; Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697., Carter D; Department of Molecular, Cell and Systems Biology, University of California, Riverside, CA 92521., Ngo LT; Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697., Solares E; Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697., Said I; Department of Biomolecular Engineering and Genomics Institute, University of California, Santa Cruz, CA 95064., Corbett-Detig RB; Department of Biomolecular Engineering and Genomics Institute, University of California, Santa Cruz, CA 95064., Gilbert LE; Department of Integrative Biology, University of Texas, Austin, TX 78712., Emerson JJ; Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697., Briscoe AD; Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697. |
| Abstrakt: |
The acquisition of novel sexually dimorphic traits poses an evolutionary puzzle: How do new traits arise and become sex-limited? Recently acquired color vision, sexually dimorphic in animals like primates and butterflies, presents a compelling model for understanding how traits become sex-biased. For example, some Heliconius butterflies uniquely possess UV (ultraviolet) color vision, which correlates with the expression of two differentially tuned UV-sensitive rhodopsins, UVRh1 and UVRh2. To discover how such traits become sexually dimorphic, we studied Heliconius charithonia , which exhibits female-specific UVRh1 expression. We demonstrate that females, but not males, discriminate different UV wavelengths. Through whole-genome shotgun sequencing and assembly of the H. charithonia genome, we discovered that UVRh1 is present on the W chromosome, making it obligately female-specific. By knocking out UVRh1 , we show that UVRh1 protein expression is absent in mutant female eye tissue, as in wild-type male eyes. A PCR survey of UVRh1 sex-linkage across the genus shows that species with female-specific UVRh1 expression lack UVRh1 gDNA in males. Thus, acquisition of sex linkage is sufficient to achieve female-specific expression of UVRh1 , though this does not preclude other mechanisms, like cis -regulatory evolution from also contributing. Moreover, both this event, and mutations leading to differential UV opsin sensitivity, occurred early in the history of Heliconius . These results suggest a path for acquiring sexual dimorphism distinct from existing mechanistic models. We propose a model where gene traffic to heterosomes (the W or the Y) genetically partitions a trait by sex before a phenotype shifts (spectral tuning of UV sensitivity). |
