視力の性分化における遺伝子の変化を初めて発見 Study identifies first known gene change in sex-differentiated vision
2023-08-10 カリフォルニア大学校アーバイン校(UCI)
◆この研究は、ヘリコギアゲハ属を調査して行われました。セグメントが欠落していたW染色体のコーディングを復元することで、蝶の性別による色覚の違いを見つけ出しました。性別による色覚差異は、花の種類の選択に影響を与えている可能性があります。
<関連情報>
- https://news.uci.edu/2023/08/10/uc-irvine-biologists-find-what-colors-a-butterflys-world/
- https://www.pnas.org/doi/10.1073/pnas.2301411120
ヘリコギアゲハにおける性二型な紫外線色覚の獲得には性連鎖遺伝子の移動が関与している Sex-linked gene traffic underlies the acquisition of sexually dimorphic UV color vision in Heliconius butterflies
Mahul Chakraborty,Angelica Guadalupe Lara,Andrew Dang,Kyle J. McCulloch,Dylan Rainbow ,David Carter,Luna Thanh Ngo,Edwin Solares,Iskander Said,Russell B. Corbett-Detig ,Lawrence E. Gilbert,J. J. Emerson, and Adriana D. Briscoe
Proceedings of the National Academy of Sciences Published:August 8, 2023
DOI:https://doi.org/10.1073/pnas.2301411120
Significance
How differences between the sexes arise and evolve is a central question in evolutionary biology. However, identifying the genetic origins of new behavioral traits has proven elusive due to the complexity of the neural circuitry underlying most behaviors and the difficulty in reconstructing complete chromosomes from whole-genome sequence data. Here, we identify one such genetic mechanism responsible for sexual dimorphism in UV (ultraviolet) color vision in the butterfly genus Heliconius—an autosomal-to-sex chromosome translocation of an opsin gene. We find that the origins of this sexually dimorphic behavior are not well explained by existing models. This represents the first known example of sex-limited UV color vision in animals due to the movement of a single gene to a sex chromosome.
Abstract
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).
