Evolutionary history of the medaka long-wavelength sensitive genes and effects of artificial regression by gene loss on behavioural photosensitivity
Evolutionary history of the medaka long-wavelength sensitive genes and effects of artificial regression by gene loss on behavioural photosensitivity
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DOI：
10.1038/s41598-019-39978-6
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发表时间：
2019-02-25
影响因子：
4.6
通讯作者：
Fukamachi, Shoji
中科院分区：
文献类型：
--
作者：
Harada, Yumi;Matsuo, Megumi;Fukamachi, Shoji
串联基因复制导致许多鱼类的视锥视蛋白谱系扩大，但由此产生的功能优势只是猜测，没有经验证明。青鳉（Oryzias latipes）和青鳉（O. sakaizumii）具有八个（两个红色、三个绿色、两个蓝色和一个紫色）视锥视蛋白基因。蛋白质的最大吸光度（λ（max））从356 nm到562 nm不等，但红色视蛋白（长波长敏感; LWS）的最大吸光度几乎相同，模糊了它们共存的必要性。在这里，我们比较了这些姐妹物种的LWS α和LWSb基因座，发现基因重复发生在早在latipes-sakaizumii物种形成之前（400 - 1800万年前），旁系同源物之间的高序列相似性是至少两次基因转换事件的结果。这些重复的基因转换表明青鳉在基因组中保留两个相同的LWS的重要性。然而，一个新建立的青鳉突变体与一个单一的LWS没有表现出缺陷的LWS表达或行为的红光敏感性，证明功能冗余的旁系同源。因此，与全基因组复制后的许多其他基因一样，冗余的LWS可能正在从当前的视锥细胞视蛋白库中丢失。因此，非等位基因的基因转换可能暂时提供了一个更容易和更频繁的解决方案比基因丢失减少遗传多样性，这应该考虑到通过系统发育分析评估基因进化的历史。
Tandem gene duplication has led to an expansion of cone-opsin repertoires in many fish, but the resulting functional advantages have only been conjectured without empirical demonstration. Medaka (Oryzias latipes and O. sakaizumii) have eight (two red, three green, two blue, and one violet) cone opsin genes. Absorbance maxima (lambda(max)) of the proteins vary from 356 nm to 562 nm, but those of the red opsins (long-wavelength sensitive; LWS) are nearly identical, obscuring the necessity of their coexistence. Here, we compared the LWS alpha and LWSb loci of these sister species and found that the gene duplication occurred long before the latipes-sakaizumii speciation (4-18 million years ago), and the high sequence similarity between the paralogues is the result of at least two events of gene conversion. These repetitive gene conversions would indicate the importance for medaka of retaining two identical LWSs in the genome. However, a newly established medaka mutant with a single LWS showed no defect in LWS expression or behavioural red-light sensitivity, demonstrating functional redundancy of the paralogs. Thus, as with many other genes after whole-genome duplication, the redundant LWS might be on the way to being lost from the current cone opsin repertoire. Thus, non-allelic gene conversion may temporarily provide an easier and more frequent solution than gene loss for reducing genetic diversity, which should be considered when assessing history of gene evolution by phylogenetic analyses.