The improved tetraploids (G1×AT) were obtained by distant crossing and gynogenesis and the high-body individuals accounted for 2% among G1×AT. After mating with each other, the high-body in- dividuals produced three kinds of bisexual fertile diploid fishes: high-body red crucian carp, high-body fork-like-tails goldfish and gray common carp. The high-body red crucian carp mating with each other formed three types of improved crucian carp (ICC) including improved red crucian carp (IRCC), im- proved color crucian carp (ICCC) and improved gray crucian carp (IGCC). The phenotypes, chromo- some numbers, gonadal structure and fertility of the three kinds of ICC and their offspring were observed. All the three kinds of ICC possessed some improved phenotypes such as higher body, smaller head and shorter tail. The ratios of the body height to body length of IRCC, ICCC and IGCC were 0.54, 0.51 and 0.54, respectively. All of them were obviously higher than that of red crucian carp 0.41 (P<0.01). Three kinds of ICC had the same chromosome number as red crucian carp with 100 chromosomes. All the ICC possessed normal gonads producing mature eggs or sperm, which was important for the production of an improved diploid population. Compared with red crucian carp, all the ICC had stronger fertility such as higher gametes production, higher fertilization rate and higher hatchery rate. Three types of improved diploid fish population were generated from the three kinds of ICC by self-crossing, respectively. The ICC can serve as ornamental fish and edible fish. They are also ideal parents to produce triploids by mating with tetraploids. The new ICC plays an important role in biological evolution and fish genetic breeding.
WANG Jing, QIN QinBo, CHEN Song, LIU ShaoJun, DUAN Wei, LIU JinHui, ZHANG Chun, LUO KaiKun, XIAO Jun & LIU Yun Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education of China, College of Life Sciences, Hunan Normal University, Changsha 410081, China
Dmc1 (disrupted meiotic cDNA) is a functionally specific gene, which was firstly discovered in yeast and then found to encode a protein required for homologous chromosome synapsis during the process of meiosis. In this investigation, we cloned the partial cDNAs of Dmc1 of diploid red crucian carp, Japanese crucian carp, common carp, triploid crucian carp and allotetraploid hybrids by using a pair of degenerate primers based on the conservative sequence of amino acids of the DMC1 protein in yeast, mouse and human. The full length cDNAs were then obtained by rapid amplification of cDNA ends (RACE). Our data showed that the full length cDNAs of Dmc1 in the three diploid fishes are all 1375 bp long, while it is 1383 bp long in triploids and 1379 bp long in allotetraploids. And despite of the variation in length, all the cDNAs encode a protein of 342 amino acids. A high homology of 97.3% of the DMC1 protein can be drawn by comparing the amino acid sequences in the three diploids, which is also of 86%, 86% and 95% similarity to human, mouse and zebrafish, respectively. A comparative study of the expression pattern of Dmc1 was carried out by RT-PCR using specific primers against the same se-quences of coding regions in different ploidy cyprinid fishes, from which it was showed that Dmc1 was expressed only in gonads of these five kinds of fishes. The expression pattern of Dmc1 in both ovaries and testes from different ploidy fishes within breeding season was also studied by Real-time PCR, and the results showed that the expression of this gene was greatly different among the three different ploidy fishes, which was the highest of triploid and lowest of allotetraploids. The histological sections data showed matured gonads of both diploid red crucian carp and allotetraploids in breeding season, although the latter demonstrated a higher maturation, and no gonadal maturation could be observed in triploids. In conclusion, we suggest that Dmc1 is specifically expressed in the period of meiosis in all the ploidy cyprinid fishes
TAO Min, LIU ShaoJun, LONG Yu, ZENG Chen, LIU JiFang, LIU LiangGuo, ZHANG Chun, DUAN Wei & LIU Yun Key Laboratory of Protein Chemistry and Developmental Biology of State Education Ministry of China, College of Life Sciences, Hunan Normal University, Changsha 410081, China
The allotetraploid hybrids of red crucian carp × common carp are the first reported artificially cultured polyploid fish with bisexual fertility and stable inheritance in vertebrate. Using ISSR and AFLP markers and the cyclins genes, the genomes and cyclin gene sequence changes were analyzed between the allotetraploid hybrids and their parents. The results indicated that the allotetraploids inherited many genetic characteristics from their parents and the genetic characteristics were stable after 15 generations. However, the allotetraploids had a closer genetic relationship with their original female parents and represented a bias toward the maternal progenitor. DNA fingerprinting analysis showed that the allotetraploids had undergone sequences deletion from their original parents and that the deleted sequences were mostly from the male parent's genome. Some non-parental bands were found in the allotetraploid hybrids. Sequences analysis of the cyclin A1 and B1 genes showed nonsynonymous substitutions of single nucleotides in codons that were different from their original parents, leading to non-parental amino acid loci. We speculate that the non-additivity in the allotetraploids, compared with their progenitors, could be an adjustment to the genomic shock from heterozygosity and polyploidy, allowing maintenance of genetic stability.
LIU LiangGuo YAN JinPeng LIU ShaoJun LIU Dong YOU CuiPing ZHONG Huan TAO Min LIU Yun
Distant hybridization makes it possible to transfer the genome of one species to another, which results in changes in phenotypes and genotypes of the progenies. This study shows that distant hybridization or the combination of this method with gynogenesis or androgenesis lead to different ploidy fishes with genetic variation, including fertile tetraploid hybrids, sterile triploid hybrids, fertile diploid hybrids, fertile diploid gynogenetic fish, and their derived progenies. The formations of the different ploidy fishes depend on the genetic relationship between the parents. In this study, several types of distant hybridization, including red crucian carp (Carassius auratus red var.) (2n=100, abbreviated as RCC) (♀)×common carp (Cyprinus carpio L.) (2n=100, abbreviated as CC) (♂), and RCC (2n=100) (♀)×blunt snout bream (Megalobrama amblycephala) (2n=48, abbreviated as BSB) (♂) are described. In the distant hybridization of RCC (♀)×CC (♂), bisexual fertile F3–F18 allotetraploid hybrids (4n=200, abbreviated as 4nAT) were formed. The diploid hybrid eggs and diploid sperm generated by the females and males of 4nAT developed into diploid gynogenetic hybrids and diploid androgenetic hybrids, respectively, by gynogenesis and androgenesis, without treatment for doubling the chromosome. Improved tetraploid hybrids and improved diploid fishes with genetic variation were derived from the gynogenetic hybrid line. The improved diploid fishes included the high-body RCC and high-body goldfish. The formation of the tetraploid hybrids was related to the occurrence of unreduced gametes generated from the diploid hybrids, which involved in premeiotic endoreduplication, endomitosis, or fusion of germ cells. The sterile triploid hybrids (3n=150) were produced on a large scale by crossing the males of tetraploid hybrids with females of diploid fish (2n=100). In another distant hybridization of RCC (♀)×BSB (♂), different ploidy fishes were obtained, including diploid bisexual fertile natural gynogenetic fish (2n=1
LIU ShaoJun Key Laboratory of Protein Chemistry and Fish Developmental Biology of Education Ministry of China, College of Life Sciences, Hunan Normal University, Changsha 410081, China
An improved triploid crucian carp(ITCC) was produced by crossing improved tetraploids(G1×AT,) with improved red crucian carp(IRCC,),which were obtained by distant crossing and gynogenesis.The biological characteristics of ITCC,including the number and karyotype of chromosomes,gonadad and pituitary structures,phenotype,and growth rate are reported.ITCC possessed 150 chromosomes with the karyotype 33m+51sm+33st+33t.In the breeding season,both ovary-like and testis-like gonads of ITCC were unable to produce normal mature gametes.The ultrastructure of the pituitary of ITCC showed that most of the endocrine granules in gonadotrophic hormone(GTH) cells had not been released,providing endocrinological evidence for the sterility of ITCC.Compared with triploid crucian carp(TCC) produced by mating Japanese crucian carp with allotetraploid hybrids,ITCC not only retained the excellent traits of fast growth rate and sterility,but also acquired improved morphological characteristics,including higher body,shorter tail and smaller head.
CHEN Song,WANG Jing,LIU ShaoJun,QIN QinBo,XIAO Jun,DUAN Wei,LUO KaiKun,LIU JinHui & LIU Yun Key Laboratory of Protein Chemistry and Developmental Biology of State Education Ministry of China,College of Life Sciences,Hunan Normal University,Changsha 410081,China
