The Evolution Of Hox Gene Clusters In Tetraploid Hybrids Derived From Red Crucian Carp×Blunt Snout Bream

Polyploidy is a widespread mechanism for speciation in eukaryotes. The distant crossing is an effective means to increase genetic variation in the hybrid progeny. With this method, it is possible to form the different ploidy offsprings including the tetraploid hybrids. Distant hybridization of red crucian carp (RCC,2n=100) and blunt snout bream (BSB,2n=48) generated tetraploid hybrids (4nRB,2n=148). Genome replication is considered to be an important impetus for the evolution of new organisms. For example, early vertebrate evolution have experienced1-2times the genome-wide complex weight. In addition, the bony fish after the opening of the differentiation of the approximately450million years ago, and terrestrial vertebrates, the genome has undergone a fish-specific genome repeat. To better understand the genome duplication in more than450million years of evolutionary process in the fish genome remodeling, the need for repeated genomic features of bony fish, the correct analysis of the fish, a large number of repeat sequences.Using11pairs of gene specific degenerate primers, we investigated the genomic organization of the Hox gene clusters in tetraploid hybrid, red crucian carp(Carassius auratus red Var.) and blunt snout bream (Megalobrama amblycephala),1,I obtained partial sequence information of32putative Hox genes in4nRB hybrids,8putative Hox genes in RCC,4putative Hox genes in BSB. All genes were amplified about700bp to1500bp, including the exon1-intron-exon2region.2,My results showed the presence of three distinct Hox duplicates in the genomes of the tetraploid hybrid, two distinct Hox duplicates in the genomes of the red crucian carp. Three distinct Hox sequences, the two of them orthologous to a Hox gene in RCC, the other one orthologous to a Hox gene in, were isolated in4nRB hybrids. However, the third "â…²" genes in4nRB hybrids don't showing an obviously orthologous relationship between RCC or BSB.3,I found that the HoxD9a, HoxD4aiii, HoxD10ai in4nRB hybrids are pseudogenes. Pseudogene, formation happens as likely via both stop codon creation as indels. Dosage effects might plausibly cause selection pressure to lose redundant Hox genes through the formation of pseudogenes. Pseudogenes are formed by random mutations that create either stop codons which prematurely terminate the full-length functional expression product, or by insertion/deletions causing a shift of the reading frame, thereby rendering the translated protein non-functional.The above findings show that the Hox genes in polyploid research as an important molecular genetic markers, while the research is of great significance in terms of biological evolution and fish genetic breeding. The results of this study will pursue the times of the early and mid-genome is still in the rapidly changing adaptability of species evolution and the evolution of species radiation and contribution, provide meaningful clues...