Weitao Song

Origin and genetic diversity of Chinese domestic ducks.

China is particularly rich in duck genetic resources. In order to reveal the genetic diversity and origin of Chinese domestic duck, the 667 bp control region of mitochondrial DNA of 238 domestic ducks from 26 indigenous breeds, 25 wild mallards and nine spot-billed ducks were sequenced and analyzed them together with the published data for 12 mallards and nine spot-billed ducks. The haplotype diversity (Hd, 0.645) and average nucleotide diversity (Pi, 0.115%) indicate low genetic diversity of Chinese domestic ducks. The NJ phylogenetic tree and reduced median-joining network chart were constructed using a total of 72 haplotypes. The genetic contribution of mallard (Anas platyrhynchos) can be detected in most of Chinese indigenous duck breeds and that of spot-billed duck (Anas zonorhyncha) can also be detected in few Chinese indigenous duck breeds. The results indicated that the Chinese domestic ducks mainly derived from mallard (A. platyrhynchos) and few derived from spot-billed duck (A. zonorhyncha).

Two maternal origins of Chinese domestic goose

China is particularly rich in goose genetic resources. Systematic study of the genetic diversity and origin of Chinese domestic geese will provide an important scientific basis for the conservation and utilization of these resources and for human history. The 521-bp control region (D-loop) of mitochondrial DNA from 26 goose breeds and 6 Landaise geese were sequenced. The results showed that the average haplotype diversity and nucleotide diversity of Chinese domestic geese were 0.1384 and 0.00029, respectively. Shared haplotype analysis and systematic evolution analysis revealed that Chinese domestic geese had 2 maternal origins. The Yili goose breed originated from the Greylag goose (Anser anser), and the other 25 domestic goose breeds originated from the swan goose (Anser cygnoides). An interesting finding was that 1 Linxian white goose and 1 Wanxi white goose shared the same H4 haplotype with the Rhine goose and the Landaise goose, which originated from the Greylag goose (A. anser). Further research on this finding is planned.

Genetic diversity and population structure of 10 Chinese indigenous egg-type duck breeds assessed by microsatellite polymorphism.

The genetic structure and diversity of 10 Chinese indigenous egg-type duck breeds were investigated using 29 microsatellite markers. The total number of animals examined were 569, on average 57 animals per breed were selected. The microsatellite marker set analysed provided 177 alleles (mean 6.1 alleles per locus, ranging from 3 to 10). All populations showed high levels of heterozygosity with the lowest estimate of 0.539 for the Jinding ducks, and the highest 0.609 observed for Jingjiang partridge ducks. The global heterozygote deficit across all populations (FIT) amounted to −0.363. About 10% of the total genetic variability originated from differences among breeds, with all loci contributing significantly. An unrooted consensus tree was constructed using the NeighborNet tree based on the Reynold’s genetic distance. The structure software was used to assess genetic clustering of these egg-type duck breeds. Clustering analysis provided an accurate representation of the current genetic relations among the breeds. An integrated analysis was undertaken to obtain information on the population dynamics in Chinese indigenous egg-type duck breeds, and to better determine the conservation priorities.

Development of skeletal muscle and expression of myogenic regulatory factors during embryonic development in Jinding ducks (Anas platyrhynchos domestica)

The important roles of myogenic regulatory factors (MRF) in mammalian skeletal myogenesis have been well studied, but few equivalent studies have been performed in poultry. The expression pattern of MRF during the embryonic development of skeletal muscle in ducks remains unknown. In this study, we identified Myf5, Myf6, MyoD, and myogenin genes in Jinding ducks (Anas platyrhynchos domestica) and quantified their expression levels in breast muscle (BM) and leg muscle (LM) at embryonic d 13, 17, 21, 25, and 27 by real-time reverse-transcription PCR. Body weight and muscle weight show different developmental patterns. The MRF genes were expressed in both BM and LM, but with different expression patterns. The MyoD gene showed lower expression levels in BM before embryonic d 21 compared with LM, whereas the opposite pattern was found later. The higher expression level of MyoD, as well its lagged expression pattern in BM, suggest that the MyoD gene may be involved in maintaining the development of different muscles. Correlation analysis showed that myogenin gene expression levels were significantly negatively correlated with BW and muscle weight in both BM and LM (P < 0.001), and MyoD and Myf6 gene expression levels were more strongly correlated with muscle weight in LM than in BM. The results of this study provide novel evidence for MRF expression in ducks in embryonic stage- and skeletal muscle-dependent manners, and provide a foundation for understanding the molecular control of skeletal muscle growth in duck breeds.

Two maternal origins of Chinese domestic light-body type goose

China is particularly rich in goose genetic resources. The systemic study of genetic diversity and origin of Chinese indigenous geese will provide important scientific basis for the conservation, utilization of resources and human history. The 521 bp control region (D-loop) of mitochondrial DNA from 13 lightbody type breeds was sequenced. The results showed that in the D-loop region of the 13 gray goose breeds, the content of T, C, A and G nucleotides was 23.8, 29.0, 32.2 and 15.1%, respectively. The average haplotype diversity (Hd) and nucleotide diversity (Pi) of domestic geese were 0.2153 and 0.00046, respectively. The 13 light-body type breeds had bigger nucleotide variance value among populations than the value within populations and all the breeds did not exist population expansion. Shared haplotype analysis and systemic systematic evolution analysis revealed that Chinese lightbody type domestic goose owned two maternal origins. YL goose breed originated from greylag goose (anser anser), and the other 12 light- body type goose breeds originated from swan goose (anser cygnoides).

Four new single nucleotide polymorphisms (SNPs) of toll-like receptor 7 gene discovered in Chinese ducks

In order to reveal the single nucleotide polymorphisms (SNPs), genotypes and allelic frequencies of each mutation site of TLR7 gene in Chinese native duck breeds, SNPs of duck TLR7 gene were detected by DNA sequencing. The genotypes of 465 native ducks from eight key protected duck breeds were determined by polymerase chain reaction ligase detection reaction (PCR-LDR) method. The results show that four new SNPs (T2606C, T2739C, C2820T and A3284G) were discovered and three genotypes were all found in each mutation site. The first and the fourth SNPs resulted in two amino acid changes of Methionine (M) → Threonine (T) and Glutamine (Q) → Arginine (R), respectively. Allele C frequency of TLR7 T2606C mutation site in Gaoyou (GY) duck breed was significantly higher than the corresponding allelic frequency in the other duck populations, and allele T frequency of TLR7 C2820T mutation site in GY duck breed was also significantly higher than the corresponding allelic frequency in the other duck populations except Putian (PT) duck breed. In conclusion, the four new SNPs and the genetic differences among different duck breeds will promote duck disease resistance research. Key words : TLR7, duck, single nucleotide polymorphism (SNP), polymerase chain reaction ligase detection reaction (PCR-LDR).

Differentiation of expression profiles of two calcineurin subunit genes in chicken skeletal muscles during early postnatal growth depending on anatomical location of muscles and breed

Abstract Calcineurin (Cn or CaN) is implicated in the control of skeletal muscle fiber phenotype and hypertrophy. However, little information is available concerning the expression of Cn in chickens. In the present study, the expression of two Cn subunit genes (CnAα and CnB1) was quantified by qPCR in the lateral gastrocnemius (LG, mainly composing of red fast-twitch myofibers), the soleus (mainly composing of red slow-twitch myofibers) and the extensor digitorum longus (EDL, mainly composing of white fast-twitch myofibers) from Qingyuan partridge chickens (QY, slow-growing chicken breed) and Recessive White chickens (RW, fast-growing chicken breed) on different days (1, 8, 22, 36, 50 and 64 days post-hatching). Although CnAα and CnB1 gene expressions were variable with different trends in different skeletal muscles in the two chicken breeds during postnatal growth, it is highly muscle phenotype and breed specific. In general, the levels of CnAα and CnB1 gene expressions of the soleus were lower than those of EDL and LG in both chicken breeds at the same stages. Compared between the two chicken breeds, the levels of CnAα gene expression of the three skeletal muscles in QY chickens were higher than those in RW chickens on days 1 and 22. However, on day 64, the levels of both CnAα and CnB1 gene expressions of the three skeletal muscles were lower in QY chickens than those in RW chickens. Correlation analysis of the levels of CnAα and CnB1 gene expressions of the same skeletal muscle showed that there were positive correlations for all three skeletal muscle tissues in two chicken breeds. These results provide some valuable clues to understand the role of Cn in the development of chicken skeletal muscles, with a function that may be related to meat quality.