论文题目：Evolution of CYP2J19, a gene involved in colour vision and red coloration in birds: positive selection in the face of conservation and pleiotropy
期刊：
作者：Hanlu Twyman et al.
发表时间：2018/2/13
数字识别码：10.1186/s12862-018-1136-y
原文链接：
最近发表的一篇研究论文为更好地理解新近确定的“发红基因”的遗传机制，对其进行了研究。
五彩金刚鹦鹉
一般认为鸟类夸张的信号，例如鲜艳的色彩，是经由两性之间的关系进化而来，其中，性形态随时间变化以抵消相反的性别特征。这些信号用于吸引合适的伴侣，而且性选择得以让更需要的特性不断传递给物种。然而，这些信号内在的遗传机制还不是非常清楚。
黑冠鹤 - Michael Möller（nopics.de），来自维基共享资源
在论文‘参与鸟类色觉和红色着色的基因CYP2J19的进化：面对基因保存和多效性的阳性选择’中，Twyman、Andersson和Mundy研究了‘发红基因’。这种最近确认的基因编码一种可修饰类胡萝卜素（一类产生红橙黄颜色的色素）的酶。
具体地，科研人员研究了CYP2J19基因是否在所有鸟类中都存在、在不同禽类谱系中的拷贝数、在鸟类基因组中的选择模式，并以织巢鸟为对象，研究了转移基因用于视觉和颜色两种功能之后，选择是否改变。
红冠蕉鹃 - Daniel Demczuk，来自维基共享资源
研究人员检测了70个禽类基因组，代表了所有主要的禽类分支。在这70个基因组中的43个检索到了单个全长CYP2J19（发红基因）。他们还分析了13种织巢鸟的发红基因序列，其中7种含有类胡萝卜素修饰酶。他们发现这种基因在鸟类的整个快速多样化期间被阳性选择，尽管原因尚不清楚。在鸟类中发现，此基因家族被阳性选择是常见的，并且没有在织巢鸟红色着色功能转变后，发现发红基因选择压力改变的证据。
这项研究的结果被发现是与祖先保留下来的红色基因的功能一致，提供色觉和皮肤及其附属物的红色着色。该基因的单拷贝在广泛的种系发生范围的鸟类谱系中被鉴别出来，表明单个CYP2J19基因是原始的鸟类状态。红色视网膜油滴几乎在所有的鸟类中都存在，但红色着色在物种之间是分布不均的。这表明CYP2J19基因对色觉的影响可能是其原始的和被广泛保留的功能。红色着色看来像是沿着特定的鸟类谱系独立发展的。
摘要：
Background
Exaggerated signals, such as brilliant colours, are usually assumed to evolve through antagonistic coevolution between senders and receivers, but the underlying genetic mechanisms are rarely known. Here we explore a recently identified “redness gene”, CYP2J19, that is highly interesting in this context since it encodes a carotenoid-modifying enzyme (a C4 ketolase involved in both colour signalling and colour discrimination in the red (long wavelength) spectral region.)
Results
A single full-length CYP2J19 was retrieved from 43 species out of 70 avian genomes examined, representing all major avian clades. In addition, CYP2J19 sequences from 13 species of weaverbirds (Ploceidae), seven of which have red C4-ketocarotenoid coloration were analysed. Despite the conserved retinal function and pleiotropy of CYP2J19, analyses indicate that the gene has been positively selected throughout the radiation of birds, including sites within functional domains described in related CYP (cytochrome P450) loci. Analyses of eight further CYP loci across 25 species show that positive selection is common in this gene family in birds. There was no evidence for a change in selection pressure on CYP2J19 following co-option for red coloration in the weaverbirds.
Conclusions
The results presented here are consistent with an ancestral conserved function of CYP2J19 in the pigmentation of red retinal oil droplets used for colour vision, and its subsequent co-option for red integumentary coloration. The cause of positive selection on CYP2J19 is unclear, but may be partly related to compensatory mutations related to selection at the adjacent gene CYP2J40.
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期刊介绍： is an open access, peer-reviewed journal that considers articles on all aspects of molecular and non-molecular evolution of all organisms, as well as phylogenetics and palaeontology.
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