Wang Yude, Sun Wenzhen, Gu Qianhong, Yao Jiajun, Tan Huifang, Huang Xu, Qin Qinbo, Tao Min, Zhang Chun, Liu Shaojun
State Key Laboratory of Developmental Biology of Freshwater Fish, Engineering Research Center of Polyploid Fish Reproduction and Breeding of the State Education Ministry, College of Life Sciences, Hunan Normal University, Changsha, China.
Front Genet. 2021 Jan 21;11:613520. doi: 10.3389/fgene.2020.613520. eCollection 2020.
Previously, a homodiploid goldfish-like fish (2 = 100; GF-L) was spontaneously generated by self-crossing a homodiploid red crucian carp-like fish (2 = 100; RCC-L), which was in turn produced via the distant hybridization of female koi carp (, KOC, 2 = 100) and male blunt snout bream (, BSB, 2 = 48). The phenotypes and genotypes of RCC-L and GF-L differed from those of the parental species but were similar to diploid red crucian carp (2 = 100; RCC) and goldfish (2 = 100; GF), respectively. We sequenced the complete mitochondrial DNAs (mtDNAs) of the KOC, BSB, RCC-L, GF-L, and subsequent generations produced by self-crossing [the self-mating offspring of RCC-L (RCC-L-F) to the self-mating offspring of RCC-L-F (RCC-L-F) and the self-mating offspring of GF-L (GF-L-F)]. Paternal mtDNA fragments were stably embedded in the mtDNAs of both lineages, forming chimeric DNA fragments. In addition to these chimeras, several nucleotide positions in the RCC-L and GF-L lineages differed from the parental bases, and were instead identical with RCC and GF, respectively. Moreover, RCC-L and GF-L mtDNA organization and nucleotide composition were more similar to those of RCC and GF, respectively, compared to parental mtDNA. Finally, phylogenetic analyses indicated that RCC-L and GF-L clustered with RCC and GF, not with the parental species. The molecular dating time shows that the divergence time of KOC and GF was about 21.26 Mya [95% highest posterior density (HPD): 24.41-16.67 Mya], which fell within the period of recent. The heritable chimeric DNA fragments and mutant loci identified in the mtDNA of the RCC-L and GF-L lineages provided important evidence that hybridizations might lead to changes in the mtDNA and the subsequent generation of new lineages. Our findings also demonstrated for the first time that the paternal mtDNA was transmitted into the mtDNA of homodiploid lineages (RCC-L and GF-L), which provided evidence that paternal DNA plays a role in inherited mtDNA. These evolutionary analyses in mtDNA suggest that GF might have diverged from RCC after RCC diverged from koi carp.
此前，通过将雌性锦鲤（, KOC, 2 = 100）与雄性团头鲂（, BSB, 2 = 48）远缘杂交产生的同源二倍体似红鲫鱼类（2 = 100；RCC-L）自交，自发产生了一种同源二倍体似金鱼类（2 = 100；GF-L）。RCC-L和GF-L的表型和基因型与亲本物种不同，但分别与二倍体红鲫（2 = 100；RCC）和金鱼（2 = 100；GF）相似。我们对KOC、BSB、RCC-L、GF-L以及自交产生的后代[RCC-L的自交后代（RCC-L-F）到RCC-L-F的自交后代（RCC-L-F）以及GF-L的自交后代（GF-L-F）]的完整线粒体DNA（mtDNA）进行了测序。父本mtDNA片段稳定地嵌入两个谱系的mtDNA中，形成嵌合DNA片段。除了这些嵌合体之外，RCC-L和GF-L谱系中的几个核苷酸位置与亲本碱基不同，而是分别与RCC和GF相同。此外，与亲本mtDNA相比，RCC-L和GF-L的mtDNA组织和核苷酸组成分别更类似于RCC和GF。最后，系统发育分析表明，RCC-L和GF-L与RCC和GF聚类，而不是与亲本物种聚类。分子定年时间表明，KOC和GF的分歧时间约为2126万年前[95%最高后验密度（HPD）：2441 - 1667万年前]，属于近代时期。在RCC-L和GF-L谱系的mtDNA中鉴定出的可遗传嵌合DNA片段和突变位点提供了重要证据，表明杂交可能导致mtDNA的变化以及新谱系的产生。我们的研究结果还首次证明父本mtDNA被传递到同源二倍体系谱（RCC-L和GF-L）的mtDNA中，这为父本DNA在遗传mtDNA中发挥作用提供了证据。这些mtDNA的进化分析表明，GF可能在RCC与锦鲤分化之后从RCC分化而来。
