|Other Abstract||The yellow catfish (Pelteobagrus fulvidraco Richardson) and the gibel carp (Carassius auratus gibelio) are both commercially important fish species in China.
In yellow catfish (Pelteobagrus fulvidraco), adult males grow about 3 times larger than female adults. Therefore, studies on the sex-linked marker, sex-determining mechanism and genetic manipulation for producing all-male population would be important and interesting subject for this species, and would be of significant benefit for yellow catfish aquaculture. Speaking to the gibel carp, in addition to its popularity in the fishery and aquarium industries, the genetic background of this species is noteworthy because it is a uniquely gynogenetic species with minor ratio of males in natural habitats, and is able to reproduce both by gynogenetic and gonochoristic modes. Hence, isolation of sex-linked markers in gibel carp would help us to explore the male origin and sex determination mechanisms in this species.
This dissertation consists of two sections. In studies on yellow catfish, a Y-linked and X-linked allele marker-assisted sex control technique for mass production of all-male yellow catfish has been developed through AFLP approach. Based on the artificial propagation families, and gynogenetic XX, XY and YY individuals obtained previously, six Y-linked and X-linked AFLP fragments were screened by sex-genotype pool bulked segregant analysis and individual screening. Interestingly, sequence analysis revealed two pairs of allelic genes from them. Furthermore, the flanking sequences were cloned and sequenced from a XY male, and a pair of locus-specific primers for Pf33 and Pf62 was respectively designed to amplify their copies from 8 XX, 8 XY and 8 YY genomes. Significantly, two alleles of Pf33 were identified and named Pf33-Y and Pf33-X with 1503bp and 1502bp, and three alleles of Pf62 were identified, and named Pf62-Y, Pf62-X, Pf62-Xs and with 1382bp, 1415bp and 1102bp respectively. According to the variations in the sequences, four Y-linked or X-linked SCAR primer pairs were designed and converted into Y-linked and X-linked SCAR markers (YSM and XSM). Consequently, the YSM and XSM were successfully used to identify genetic sex and YY super-male, and applied to all-male population production. According to the results, a novel and simple technique system for commercial production of YY super-males and all-male populations was suggested in the yellow catfish.
The other part is about the gibel carp. In this study, a male-biased mutant family was discovered from the gynogenetic gibel carp, and a male-specific allele was identified from the mutant family. Firstly, normal spermatogenesis was observed in the testes of males in the mutant family by immunofluorescence histochemistry. Testing cross demonstrate that the 2.8% females were genetic females and the male-determined genetic materials in the mutant males can transmit to the next generation. Subsequently, nearly identical AFLP profiles were observed between males and females in the male-biased mutant family, but a male-specific 86bp AFLP fragment was screened by sex-pool bulked segregant analysis and individual screening. Based on the 86bp male-specific AFLP fragment, a total of 4016bp flanking sequences of this male-specific AFLP fragment were obtained by genome walking, and a male-specific SCAR marker was designed, and the male-specific DNA fragment was confirmed to be steadily transmitted to the next generation and to be consistently detected only in males. Furthermore, six homologous sequences of the male-specific sequence were identified from genomes of male and female Gibel carp clone D and clone A and diploid Carassius auratus, and phylogenetic analysis of these homologous sequences indicated that the male-specific allele of Gibel carp was genetically more related to the homologous sequence identified from diploid Carassius auratus. Moreover, the 4016bp male-specific sequence revealed a novel SET domain gene CagSET-M, which was subsequently identified to be specially transcribed in testis of adult male Gibel carp. Then, a Smart cDNA library of testis of Gibel carp was constructed, and the full length of CagSET-M was cloned by RACE approach. Finally, the male determination and male origin of gibel carp were discussed.|