Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
Proc Natl Acad Sci U S A. 2010 Feb 23;107(8):3628-33. doi: 10.1073/pnas.0910085107. Epub 2010 Feb 2.
The butterfly Heliconius erato can see from the UV to the red part of the light spectrum with color vision proven from 440 to 640 nm. Its eye is known to contain three visual pigments, rhodopsins, produced by an 11-cis-3-hydroxyretinal chromophore together with long wavelength (LWRh), blue (BRh) and UV (UVRh1) opsins. We now find that H. erato has a second UV opsin mRNA (UVRh2)-a previously undescribed duplication of this gene among Lepidoptera. To investigate its evolutionary origin, we screened eye cDNAs from 14 butterfly species in the subfamily Heliconiinae and found both copies only among Heliconius. Phylogeny-based tests of selection indicate positive selection of UVRh2 following duplication, and some of the positively selected sites correspond to vertebrate visual pigment spectral tuning residues. Epi-microspectrophotometry reveals two UV-absorbing rhodopsins in the H. erato eye with lambda(max) = 355 nm and 398 nm. Along with the additional UV opsin, Heliconius have also evolved 3-hydroxy-DL-kynurenine (3-OHK)-based yellow wing pigments not found in close relatives. Visual models of how butterflies perceive wing color variation indicate this has resulted in an expansion of the number of distinguishable yellow colors on Heliconius wings. Functional diversification of the UV-sensitive visual pigments may help explain why the yellow wing pigments of Heliconius are so colorful in the UV range compared to the yellow pigments of close relatives lacking the UV opsin duplicate.
蝴蝶海伦娜(Heliconius erato)可以用颜色视觉看到紫外线到光谱的红光部分,其颜色视觉已被证明在 440 到 640nm 之间。已知其眼睛中含有三种视色素,即视紫红质,由 11-顺式-3-羟基视黄醛发色团与长波(LWRh)、蓝光(BRh)和紫外线(UVRh1)视蛋白一起产生。我们现在发现海伦娜蝴蝶有第二个紫外线视蛋白 mRNA(UVRh2)-这是鳞翅目昆虫中该基因以前未描述的重复。为了研究其进化起源,我们从 14 种海伦娜蝴蝶亚科的眼睛 cDNA 中进行筛选,仅在海伦娜蝴蝶中发现了这两个拷贝。基于系统发育的选择测试表明,紫外线视蛋白基因重复后发生了正选择,一些正选择位点与脊椎动物视觉色素光谱调谐残基相对应。外显子微分光光度法揭示了海伦娜蝴蝶眼睛中的两种吸收紫外线的视紫红质,其最大吸收波长分别为 355nm 和 398nm。除了额外的紫外线视蛋白,海伦娜蝴蝶还进化出了基于 3-羟基-DL-犬尿氨酸(3-OHK)的黄色翅膀色素,而其近缘种中则没有这种色素。蝴蝶对翅膀颜色变化的视觉模型表明,这导致了海伦娜蝴蝶翅膀上可区分的黄色数量的增加。紫外线敏感视蛋白的功能多样化可能有助于解释为什么与缺乏紫外线视蛋白重复的近缘种相比,海伦娜蝴蝶的黄色翅膀色素在紫外线范围内如此丰富多彩。