Data from: Variation in opsin genes correlates with signaling ecology in North American fireflies

Genes underlying signal reception should evolve to maximize signal detection in a particular environment. In animals, opsins, the protein component of visual pigments, are predicted to evolve according to this expectation. Fireflies are known for their bioluminescent mating signals. The eyes of nocturnal species are expected to maximize detection of conspecific signal colors emitted in the typical low-light environment. This is not expected for species that have transitioned to diurnal activity in bright daytime environments. Here we test the hypothesis that opsin gene sequence plays a role in modifying firefly eye spectral sensitivity. We use genome and transcriptome sequencing in four firefly species, transcriptome sequencing in six additional species, and targeted gene sequencing in 28 other species to identify all opsin genes present in North American fireflies and to elucidate amino acid sites under positive selection. We also determine whether amino acid substitutions in opsins are linked to evolutionary changes in signal mode, signal color, and light environment. We find only two opsins, one long wavelength and one ultraviolet, in all firefly species and identify 25 candidate sites that may be involved in determining spectral sensitivity. In addition, we find elevated rates of evolution at transitions to diurnal activity, and changes in selective constraint on LW opsin associated with changes in light environment. Our results suggest that changes in eye spectral sensitivity are at least partially due to opsin sequence. Fireflies continue to be a promising system in which to investigate the evolution of signals, receptors, and signaling environments.参与信号接收的基因应在特定环境中进化以最大化信号探测效率。在动物体内，视蛋白（opsins）作为视觉色素的蛋白组分，其进化模式符合这一预期。萤火虫以其生物发光的求偶信号而广为人知。夜行性萤火虫的眼睛应在典型弱光环境下最大化探测同种个体的信号色彩，而那些转变为日间活动、栖息于明亮白昼环境的物种则无此进化预期。本研究旨在验证如下假说：视蛋白基因序列在调控萤火虫眼睛的光谱敏感性中发挥作用。我们对4种萤火虫进行基因组与转录组测序，对另外6种萤火虫开展转录组测序，并对另外28种萤火虫实施靶向基因测序，以此鉴定北美萤火虫体内存在的全部视蛋白基因，并阐明处于正选择压力下的氨基酸位点。此外，我们还探究了视蛋白的氨基酸替换是否与信号模式、信号色彩及光照环境的进化改变存在关联。我们在所有萤火虫物种中仅发现两种视蛋白：一种为长波长视蛋白，另一种为紫外视蛋白，并鉴定出25个可能参与调控光谱敏感性的候选氨基酸位点。此外，我们发现在转变为日间活动的类群中，视蛋白的进化速率有所提升，且长波长视蛋白的选择约束变化与光照环境的改变相关联。本研究结果表明，萤火虫眼睛光谱敏感性的改变至少部分源于视蛋白基因序列的变化。萤火虫仍是研究信号、受体及信号环境进化的极具潜力的研究体系。