Nikaido Masato, Ota Tomoki, Hirata Tadashi, Suzuki Hikoyu, Satta Yoko, Aibara Mitsuto, Mzighani Semvua I, Sturmbauer Christian, Hagino-Yamagishi Kimiko, Okada Norihiro
Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
Department of Biosystems Science, School of Advanced Sciences, The Graduate University for Advanced Studies (Sokendai), Hayama, Japan.
Genome Biol Evol. 2014 May 6;6(5):1135-44. doi: 10.1093/gbe/evu086.
Fish use olfaction to detect a variety of nonvolatile chemical signals, and thus, this sense is key to survival and communication. However, the contribution of the olfactory sense to social-especially reproductive-interactions in cichlids is still controversial. To obtain insights into this issue, we investigated the genes encoding V1Rs-possible candidates for reproductive pheromone receptors-among East-African cichlids. Interestingly, we found an excess of nonsynonymous over synonymous substitutions in four of six V1R genes in multiple cichlid lineages. First, we found that highly dimorphic V1R2 allele groups were shared among the cichlids inhabiting all East-African Great Lakes emerged through the episodic accumulation of the nonsynonymous substitutions prior to the radiation of the Lake Tanganyika species flock. We further detected such episodic events in V1R1 of the tribe Tropheini, and in V1R3 and V1R6 of the tribe Trematocarini. The excess of nonsynonymous substitutions in these examples were indicated as dN/dS > 1, which were all statistically significant by Fisher's exact test. Furthermore, we speculate that the amino acid changes in these episodic events are likely functional switch because they occurred in the putative ligand-binding pocket. Our finding of the occurrence of multiple episodic events and the unexpected gene diversity in one unique gene family is suggestive of the contribution of the V1R to the species diversification and the social interaction in cichlids.
鱼类利用嗅觉来检测各种非挥发性化学信号，因此，这种感官对于生存和交流至关重要。然而，嗅觉在丽鱼科鱼类的社会互动尤其是生殖互动中的作用仍存在争议。为了深入了解这个问题，我们研究了东非丽鱼科鱼类中编码V1Rs（生殖信息素受体的可能候选基因）的基因。有趣的是，我们发现多个丽鱼科谱系中六个V1R基因中的四个存在非同义替换多于同义替换的情况。首先，我们发现高度二态的V1R2等位基因组在所有东非大湖的丽鱼科鱼类中都有共享，这些等位基因组是在坦噶尼喀湖物种群辐射之前通过非同义替换的偶发积累而出现的。我们还在Tropheini部落的V1R1以及Trematocarini部落的V1R3和V1R6中检测到了这种偶发事件。这些例子中非同义替换的过量表现为dN/dS > 1，通过费舍尔精确检验，这些结果均具有统计学意义。此外，我们推测这些偶发事件中的氨基酸变化可能是功能性开关，因为它们发生在假定的配体结合口袋中。我们发现多个偶发事件的发生以及一个独特基因家族中意外的基因多样性，这表明V1R对丽鱼科鱼类的物种多样化和社会互动有贡献。
