Laboratory of Aquatic Zoology, Marine Research Station, Institute of Cellular and Organismic Biology, Academia Sinica, Yilan, 26242, Taiwan.
Division of Developmental Biology, Department of Functional Morphology, Faculty of Medicine, School of Life Science, Tottori University, Nishi-Cho 86, Yonago, 683-8503, Japan.
Sci Rep. 2022 Nov 19;12(1):19961. doi: 10.1038/s41598-022-24444-7.
Breeders and fanciers have established many peculiar morphological phenotypes in ornamental goldfish. Among them, the twin-tail and dorsal-finless phenotypes have particularly intrigued early and recent researchers, as equivalent morphologies are extremely rare in nature. These two mutated phenotypes appeared almost simultaneously within a short time frame and were fixed in several strains. However, little is known about how these two different mutations could have co-occurred during such a short time period. Here, we demonstrate that the chordin gene, a key factor in dorsal-ventral patterning, is responsible not only for the twin-tail phenotype but also for the dorsal-finless phenotype. Our F2 backcrossing and functional analyses revealed that the penetrance/expressivity of the dorsal-finless phenotype can be suppressed by the wild-type allele of chdS. Based on these findings, we propose that chdS may have masked the expression of the dorsal-finless phenotype, acting as a capacitor buffering gene to allow accumulation of genetic mutations. Once this gene lost its original function in the twin-tail goldfish lineages, the dorsal-finless phenotype could be highly expressed. Thus, this study experimentally demonstrates that the rapid genetic fixation of morphological mutations during a short domestication time period may be related to the robustness of embryonic developmental mechanisms.
养殖者和爱好者在观赏金鱼中建立了许多特殊的形态表型。其中，双尾和无背鳍表型特别引起了早期和近期研究人员的兴趣，因为在自然界中，等价的形态极为罕见。这两种突变表型几乎同时在很短的时间内出现，并在几个品系中固定下来。然而，对于这两种不同的突变如何在如此短的时间内同时发生，人们知之甚少。在这里，我们证明了 chordin 基因，一种背腹模式形成的关键因素，不仅负责双尾表型，还负责无背鳍表型。我们的 F2 回交和功能分析表明，野生型 chdS 等位基因可以抑制无背鳍表型的外显率/表现度。基于这些发现，我们提出 chdS 可能掩盖了无背鳍表型的表达，作为一个电容器缓冲基因，允许遗传突变的积累。一旦这个基因在双尾金鱼谱系中失去了原有的功能，无背鳍表型就可以高度表达。因此，这项研究从实验上证明了在短时间的驯化过程中，形态突变的快速遗传固定可能与胚胎发育机制的稳健性有关。
