Institute of hydrology, Chinese Academy of Sciences, etc. revealed the evolutionary mechanism of successful Parthenogenesis of double triploid crucian carp
By: Date: 2022-07-15 Categories: foodtechnology Tags: ,
Parthenogenesis lacks meiotic homologous recombination, which leads to the accumulation of harmful mutations and hinders the production of genetic diversity. Therefore, parthenogenesis is usually considered as an evolutionary”dead end”. Some monogamous fish and reptiles have existed for far longer than their predicted extinction time, and show high genetic diversity and strong environmental adaptability. However, the evolutionary mechanism of vertebrate parthenogenesis is still unclear.
 
Recently, the team of GUI Jianfang, an academician of the Chinese Academy of Sciences and a researcher of the Institute of Hydrobiology of the Chinese Academy of Sciences, the team of Wang Wen, a professor of Northwestern Polytechnic University, and the team of Fang Xiaodong, a professor of BGI, have deeply cooperated to reveal the evolutionary mystery of reproductive success of silver crucian carp with hexaploid gynogenesis as the research object.
 
The research team sequenced the whole genome of sexually reproductive tetraploid crucian carp (crucian carp:carassius auratus) and gynogenetic hexaploid silver crucian carp (gibel carp:carassius gibelio), and assembled the haplotype genome at the chromosome level. Studies have shown that their haplotype genomes contain 50 chromosomes, including two sub genomes (25 chromosomes from sub genome a and 25 chromosomes from sub genome b). Sequencing coverage analysis found that tetraploid crucian carp is amphidiploid (AABB), which contains two sets of diploid genome, each set of diploid genome from different ancestors; It is revealed that hexaploid crucian carp is amphitriploid (aaabbb), which contains two sets of triploid genomes, each set of triploid genomes derived from different ancestors.
 
According to the resequencing data of different strains of double diploid crucian carp and double triploid silver crucian carp, the double triploid silver crucian carp was formed from the ancestor double diploid crucian carp by homologous triploidization about 820000-96000 years ago. Through gynogenesis, the double triploid crucian carp overcomes the reproductive barrier of three homologous chromosomes that cannot be paired normally and separated equally. Comparative genomics analysis showed that meiosis cell cycle related genes and an oocyte specific histone variant had a large expansion in gynogenetic crucian carp, and most of the expansion genes were expressed in ovaries and oocytes. In addition, cytological observation showed that the double triploid crucian carp produced unreduced eggs by inhibiting the first meiotic division, and sporadic homologous recombination events and high gene conversion rates were detected during egg maturation. These genomic changes may be conducive to the elimination of harmful mutations and the maintenance of genomic stability in the double triploid crucian carp.
 
This study first proposed the concept of double triploid. The analyzed genome of crucian carp is the first double triploid genome, which provides innovative insights into the evolutionary mechanism of successful reproduction of haploid vertebrates, and provides valuable resources for promoting precise genetic breeding of crucian carp.
 
The relevant research results are comparative genome analysis reviews evolutioNary insights into a unique amphitriploid fish, published in nature ecology & Evolution. The research work has been supported by the strategic leading science and technology project of the Chinese Academy of Sciences, the key research plan of Frontier Science of the Chinese Academy of Sciences and the national key research and development plan.