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Comparative genome anatomy reveals evolutionary insights into a unique amphitriploid fish

2022; Nature Portfolio; Volume: 6; Issue: 9 Linguagem: Inglês

10.1038/s41559-022-01813-z

2397-334X

Yang Wang, Xi‐Yin Li, Wenjie Xu, Kun Wang, Bin Wu, Meng Xu, Yan Chen, Lijun Miao, Zhongwei Wang, Zhi Li, Xiaojuan Zhang, Zhan Yin, Botong Zhou, Yulan Yang, Chenglong Zhu, Mingliang Hu, Jiang-Ming Zheng, Chenguang Feng, Qiang Qiu, Letian Tian, Meng Lu, Fang Peng, Wei-Jia Lu, Jin-Feng Tong, Jingou Tong, Beide Fu, Peng Yu, Miao Ding, Rui-Hai Gan, Qinqin Zhang, Jianbo Jian, Chi Zhang, Weiming He, Wei Yang, Zicheng Zhao, Qianqian Zhang, Qiang Gao, Junyang Xu, Mingzhou Bai, Ya‐Ping Zhang, Huanming Yang, Xiaodong Fang, Wen Wang, Li Zhou, Jian‐Fang Gui,

Genetic diversity and population structure

Abstract Triploids are rare in nature because of difficulties in meiotic and gametogenic processes, especially in vertebrates. The Carassius complex of cyprinid teleosts contains sexual tetraploid crucian carp/goldfish ( C. auratus ) and unisexual hexaploid gibel carp/Prussian carp ( C. gibelio ) lineages, providing a valuable model for studying the evolution and maintenance mechanism of unisexual polyploids in vertebrates. Here we sequence the genomes of the two species and assemble their haplotypes, which contain two subgenomes (A and B), to the chromosome level. Sequencing coverage analysis reveals that C. gibelio is an amphitriploid (AAABBB) with two triploid sets of chromosomes; each set is derived from a different ancestor. Resequencing data from different strains of C. gibelio show that unisexual reproduction has been maintained for over 0.82 million years. Comparative genomics show intensive expansion and alterations of meiotic cell cycle-related genes and an oocyte-specific histone variant. Cytological assays indicate that C. gibelio produces unreduced oocytes by an alternative ameiotic pathway; however, sporadic homologous recombination and a high rate of gene conversion also exist in C. gibelio . These genomic changes might have facilitated purging deleterious mutations and maintaining genome stability in this unisexual amphitriploid fish. Overall, the current results provide novel insights into the evolutionary mechanisms of the reproductive success in unisexual polyploid vertebrates.