Selection, drift, and constraint in cypridinid luciferases and the diversification of bioluminescent signals in sea fireflies
Selection, drift, and constraint in cypridinid luciferases and the diversification of bioluminescent signals in sea fireflies
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DOI：
10.1111/mec.15673
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发表时间：
2020-11-05
影响因子：
4.9
通讯作者：
Oakley, Todd H.
中科院分区：
文献类型：
--
作者：
Hensley, Nicholai M.;Ellis, Emily A.;Oakley, Todd H.
了解进化多样化的遗传原因具有挑战性，因为物种之间的差异很复杂，通常涉及许多基因。然而，单个或少数遗传位点影响在物种辐射中显著变化的性状的情况为理解多样化的遗传学提供了容易的机会。在这里，我们开始探索塞浦路斯介形虫（“海萤火虫”）物种间生物发光信号的多样化是如何受到塞浦路斯-荧光素酶单一基因进化的影响的。除了21个塞浦路斯物种生物发光的发射光谱（“颜色”）外，我们还报道了来自新生转录组的13个新的c-荧光素酶基因，包括确认其中4个基因功能的体外测定。我们的比较分析表明，c-荧光素酶中的一些氨基酸位点是在偶发性多样化选择下进化的，可能与酶动力学和颜色的变化有关，这两种酶的功能直接影响生物发光信号的表型。分析还表明，c-荧光素酶中的多个其他氨基酸位置是在中性或净化选择下进化的，并且可能影响了属间生物发光信号的颜色变化。先前在候选位点的诱变研究显示上位性相互作用，这可能限制c-荧光素酶功能的进化。这项工作为理解多物种行为信号多样化的遗传基础提供了重要的步骤，表明在物种辐射期间，不同的进化过程在不同的时间起作用。这些结果为进一步的诱变研究奠定了基础，这些研究可以明确地将选择、漂变和约束与表型多样化的进化联系起来。
Understanding the genetic causes of evolutionary diversification is challenging because differences across species are complex, often involving many genes. However, cases where single or few genetic loci affect a trait that varies dramatically across a radiation of species provide tractable opportunities to understand the genetics of diversification. Here, we begin to explore how diversification of bioluminescent signals across species of cypridinid ostracods ("sea fireflies") was influenced by evolution of a single gene, cypridinid-luciferase. In addition to emission spectra ("colour") of bioluminescence from 21 cypridinid species, we report 13 new c-luciferase genes from de novo transcriptomes, including in vitro assays to confirm function of four of those genes. Our comparative analyses suggest some amino acid sites in c-luciferase evolved under episodic diversifying selection and may be associated with changes in both enzyme kinetics and colour, two enzymatic functions that directly impact the phenotype of bioluminescent signals. The analyses also suggest multiple other amino acid positions in c-luciferase evolved neutrally or under purifying selection, and may have impacted the variation of colour of bioluminescent signals across genera. Previous mutagenesis studies at candidate sites show epistatic interactions, which could constrain the evolution of c-luciferase function. This work provides important steps toward understanding the genetic basis of diversification of behavioural signals across multiple species, suggesting different evolutionary processes act at different times during a radiation of species. These results set the stage for additional mutagenesis studies that could explicitly link selection, drift, and constraint to the evolution of phenotypic diversification.