title: Formation of diploid and triploid hybrid groupers (hybridization of Epinephelus coioides ♀ × Epinephelus lanceolatus ♂) and their 5S gene analysis.
abstract: Interspecies hybridization is widely used to achieve heterosis or hybrid vigor, which has been observed and harnessed by breeders for centuries. Natural allopolyploid hybrids generally exhibit more superior heterosis than both the diploid progenies and their parental species. However, polyploid formation processes have been long ignored, the genetic basis of heterosis in polyploids remains elusive.
  
  
  
  In the present study, triploid hybrids had been demonstrated to contain two sets of chromosomes from mother species and one set from father species. Cellular polyploidization process in the embryos had been traced. The triploid hybrids might be formed by failure formation of the second polarized genome during the second meiosis stage. Four spindle centers were observed in anaphase stage of the first cell division. Three spindle centers were observed in side of cell plate after the first cell division. The 5S rDNA genes of four types of groupers were cloned and analyzed. The diploid and triploid hybrids had been proved to contain the tandem chimera structures which were recombined by maternal and paternal monomer units. The results indicated that genome re-fusion had occurred in the hybrid progenies. To further elucidate the genetic patterns of diploid and triploid hybrids, fluorescence chromosome location had been carried out, maternal 5S gene (M-386) were used as the probe. The triploid hybrids contained fewer fluorescence loci numbers than the maternal species. The results indicated that participation of paternal 5S gene in the triploid hybrid genome had degraded the match rates of M-386 probe.
  
  
  
  Our study is the first to investigate the cellular formation processes of natural allopolyploids in hybrid fish, the cellular polyploidization process may be caused by failure formation of the second polarized genome during the meiosis, and our results will provide the molecular basis of hybrid vigor in interspecies hybridization.
authors.affiliation: State Key Laboratory of Biocontrol, Institute of Aquatic Economic Animals, and the Guangdong Province Key Laboratory for Aquatic Economic Animals, Sun Yat-Sen University, Guangzhou, 510275, China.|Key Laboratory of Tropical Marine Bio-resources and Ecology (LMB) and Guangdong Provincial Key Laboratory of Applied Marine Biology (LAMB), South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.|South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Guangzhou, 510275, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Huang
authors.affiliation: Key Laboratory of Protein Chemistry and Developmental Biology of the State Education Ministry of China, College of Life Sciences, Hunan Normal University, Changsha, 410081, China.
authors.forename: Qinbo
authors.initials: Q
authors.lastname: Qin
authors.affiliation: College of Animal Science, South China Agricultural University, Guangzhou, 510642, China.
authors.forename: Huirong
authors.initials: H
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Biocontrol, Institute of Aquatic Economic Animals, and the Guangdong Province Key Laboratory for Aquatic Economic Animals, Sun Yat-Sen University, Guangzhou, 510275, China.
authors.forename: Shuisheng
authors.initials: S
authors.lastname: Li
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology (LMB) and Guangdong Provincial Key Laboratory of Applied Marine Biology (LAMB), South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.|South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Guangzhou, 510275, China.
authors.forename: Chaoqun
authors.initials: C
authors.lastname: Hu
authors.affiliation: Key Laboratory of Protein Chemistry and Developmental Biology of the State Education Ministry of China, College of Life Sciences, Hunan Normal University, Changsha, 410081, China.
authors.forename: Yude
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Biocontrol, Institute of Aquatic Economic Animals, and the Guangdong Province Key Laboratory for Aquatic Economic Animals, Sun Yat-Sen University, Guangzhou, 510275, China. lsszy@mail.sysu.edu.cn.|South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Guangzhou, 510275, China. lsszy@mail.sysu.edu.cn.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Protein Chemistry and Developmental Biology of the State Education Ministry of China, College of Life Sciences, Hunan Normal University, Changsha, 410081, China. lsj@hunnu.edu.cn.
authors.forename: Shaojun
authors.initials: S
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Biocontrol, Institute of Aquatic Economic Animals, and the Guangdong Province Key Laboratory for Aquatic Economic Animals, Sun Yat-Sen University, Guangzhou, 510275, China.|South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Guangzhou, 510275, China.
authors.forename: Haoran
authors.initials: H
authors.lastname: Lin
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D004171:Diploidy; D047108:Embryonic Development / Q000235:genetics; D005260:Female; D005399:Fishes / Q000196:embryology / Q000235:genetics*; D006823:Hybrid Vigor / Q000235:genetics*; D006824:Hybridization, Genetic; D059785:Karyotype; D007621:Karyotyping; D008297:Male; D012341:RNA, Ribosomal, 5S / Q000235:genetics; D057885:Triploidy
chemical_list: D012341:RNA, Ribosomal, 5S
keywords: 5S gene; Embryo development; Grouper; Heterosis; Natural polyploidization