Whole-genome sequencing revealed genetic diversity, structure and patterns of selection in Guizhou indigenous chickens.

BACKGROUND: The eight phenotypically distinguishable indigenous chicken breeds in Guizhou province of China are great resources for high-quality development of the poultry industry in China. However, their full value and potential have yet to be understood in depth. To illustrate the genetic diversity, the relationship and population structure, and the genetic variation patterns shaped by selection in Guizhou indigenous chickens, we performed a genome-wide analysis of 240 chickens from 8 phenotypically and geographically representative Guizhou chicken breeds and 60 chickens from 2 commercial chicken breeds (one broiler and one layer), together with 10 red jungle fowls (RJF) genomes available from previous studies. RESULTS: The results obtained in this present study showed that Guizhou chicken breed populations harbored higher genetic diversity as compared to commercial chicken breeds, however unequal polymorphisms were present within Guizhou indigenous chicken breeds. The results from the population structure analysis markedly reflected the breeding history and the geographical distribution of Guizhou indigenous chickens, whereas, some breeds with complex genetic structure were ungrouped into one cluster. In addition, we confirmed mutual introgression within Guizhou indigenous chicken breeds and from commercial chicken breeds. Furthermore, selective sweep analysis revealed candidate genes which were associated with specific and common phenotypic characteristics evolved rapidly after domestication of Guizhou local chicken breeds and economic traits such as egg production performance, growth performance, and body size. CONCLUSION: Taken together, the results obtained from the comprehensive analysis of the genetic diversity, genetic relationships and population structures in this study showed that Guizhou indigenous chicken breeds harbor great potential for commercial utilization, however effective conservation measures are currently needed. Additionally, the present study drew a genome-wide selection signature draft for eight Guizhou indigenous chicken breeds and two commercial breeds, as well as established a resource that can be exploited in chicken breeding programs to manipulate the genes associated with desired phenotypes. Therefore, this study will provide an essential genetic basis for further research, conservation, and breeding of Guizhou indigenous chickens.

[Screening genes related to 'black' character in wu-ding chicken by delta differential display].

The 'black' character is a cardinal character of black chicken that is very important to the medical value and economical value of black chicken. The study compared gene expression between black chicken and non-black chicken by delta differential display method, and obtained twenty-nine expressed sequence tags(ESTs) by extraction, amplification, purification, northern blotting, cloning and sequencing of gel-embedded DNA. Of twenty-nine ESTs, eight ESTs have high similarity rate with known gene in chicken-beta-trepomyosin gene, cardiac myosin alkali light chain gene, insertionally activated c-Ha-ras oncogene, fra-2 oncogene, 16S rRNA gene and mitochondrion genome sequence, respectively, with similarity rate 97%,100%, 98%, 98%, 98%, 99%, 99% and 97%. Five ESTs have high similarity rate with human TTN gene, human phosphoglucomutase 5 gene, human or mouse signal recongnition particle 54 kD gene, human or mouse ribonuclease/angiogenin inhibitor gene, respectively, with similarity rate 82%, 82%, 87%, 99% and 99%. Their homologous genes in chicken are still not cloned. Thirteen ESTs are novel gene fragments. Of thirteen ESTs, nine ESTs have high similarity with ESTs in database. Four ESTs have not high similarity with any EST in database. The results of gene expression analysis show that one known gene (insertionally activated c-Ha-ras oncogene) fragment and one novel gene fragment are expressed in all non-black chicken and are not expressed in all black chicken, and that one known gene (signal recongnition particle 54 kD gene) fragment is expressed in all black chicken and is not expressed in all non-black chicken. According to these results, we conclude that the expression of insertionally activated c-Ha-ras oncogene, signal recongnition particle 54 kD gene and one novel gene are related to the 'black' character in chicken.