Evolution of the cichlid visual palette through ontogenetic subfunctionalization of the opsin gene arrays
Evolution of the cichlid visual palette through ontogenetic subfunctionalization of the opsin gene arrays
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DOI：
10.1093/molbev/msl014
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发表时间：
2006-08-01
影响因子：
10.7
通讯作者：
Carleton, Karen L.
中科院分区：
文献类型：
--
作者：
Spady, Tyrone C.;Parry, Juliet W. L.;Carleton, Karen L.
视锥蛋白基因的进化是一个通过基因复制和丢失而产生和死亡的动态过程。然而，控制视蛋白基因保留和死亡的力量尚不清楚。非洲慈鲷有一系列的生态，不同的栖息地和觅食方式，这使它们成为研究作用于视蛋白基因家族的选择力的理想选择。在这项工作中，我们提供了关于河流慈鲷的数据，Oreochromis niloticus，这是大非洲湖泊中慈鲷适应辐射的祖先外群。我们鉴定了7个视锥蛋白基因与几个基因复制的实例。我们还通过视觉色素的重建来表征这些基因的光谱敏感性。峰吸光度表明，每个罗非鱼视蛋白基因编码一种光谱上不同的视觉色素：SWS1 （360 nm）、SWS2b （423 nm）、SWS2a （456nm）、Rh2b （472 nm）、Rh2a P （518 nm）、Rh2a alpha （528 nm）和LWS （561 nm）。此外，3个个体发生时间点的定量逆转录聚合酶链反应表明，虽然在成人中只有4个基因（SWS2a、Rh2a α和β以及LWS）表达，但其他基因的mrna都在个体发生时表达。因此，通过个体发育差异表达的亚功能化可能是视蛋白基因保存的关键机制。这些保存的视蛋白基因的不同的峰值吸收提供了一个调色板，从中选择创造了在湖泊适应辐射的慈鲷物种中发现的不同的视觉敏感性。
The evolution of cone opsin genes is characterized by a dynamic process of gene birth and death through gene duplication and loss. However, the forces governing the retention and death of opsin genes are poorly understood. African cichlid fishes have a range of ecologies, differing in habitat and foraging style, which make them ideal for examining the selective forces acting on the opsin gene family. In this work, we present data on the riverine cichlid, Oreochromis niloticus, which is an ancestral outgroup to the cichlid adaptive radiations in the Great African lakes. We identify 7 cone opsin genes with several instances of gene duplication. We also characterize the spectral sensitivities of these genes through reconstitution of visual pigments. Peak absorbances demonstrate that each tilapia cone opsin gene codes for a spectrally distinct visual pigment: SWS1 (360 nm), SWS2b (423 nm), SWS2a (456 nm), Rh2b (472 nm), Rh2a P (518 nm), Rh2a alpha (528 nm), and LWS (561 nm). Furthermore, quantitative reverse transcription polymerase chain reaction at 3 ontogenetic time points demonstrates that although only 4 genes (SWS2a, Rh2a alpha and beta, and LWS) are expressed in adults, mRNAs for the other genes are all expressed during ontogeny. Therefore, subfunctionalization through differential ontogenetic expression may be a key mechanism for preservation of opsin genes. The distinct peak absorbances of these preserved opsin genes provide a palette from which selection creates the diverse visual sensitivities found among the cichlid species of the lacustrine adaptive radiations.