Polymorphisms of melatonin receptor genes and their associations with egg production traits in Shaoxing duck

Objective

In birds, three types of melatonin receptors (MTNR1A, MTNR1B, and MTNR1C) have been cloned. Previous researches have showed that three melatonin receptors played an essential role in reproduction and ovarian physiology. However, the association of polymorphisms of the three receptors with duck reproduction traits and egg quality traits is still unknown. In this test, we chose MTNR1A, MTNR1B, and MTNR1C as candidate genes to detect novel sequence polymorphism and analyze their association with egg production traits in Shaoxing duck, and detected their mRNA expression level in ovaries.

Methods

In this study, a total of 785 duck blood samples were collected to investigate the association of melatonin receptor genes with egg production traits and egg quality traits using a direct sequencing method. And 6 ducks representing two groups (3 of each) according to the age at first eggs (at 128 days of age or after 150 days of age) were carefully selected for quantitative real-time polymerase chain reaction.

Results

Seven novel polymorphisms (MTNR1A: g. 268C>T, MTNR1B: g. 41C>T, and g. 161T>C, MTNR1C: g. 10C>T, g. 24A>G, g. 108C>T, g. 363 T>C) were detected. The single nucleotide polymorphism (SNP) of MTNR1A (g. 268C>T) was significantly linked with the age at first egg (p<0.05). And a statistically significant association (p<0.05) was found between MTNR1C g.108 C>T and egg production traits: total egg numbers at 34 weeks old of age and age at first egg. In addition, the mRNA expression level of MTNR1A in ovary was significantly higher in late-mature group than in early-mature group, while MTNR1C showed a contrary tendency (p<0.05).

Conclusion

These results suggest that identified SNPs in MTNR1A and MTNR1C may influence the age at first egg and could be considered as the candidate molecular marker for identify early maturely traits in duck selection and improvement.

Novel Polymorphisms of Adrenergic, Alpha-1B-, Receptor and Peroxisome Proliferator-activated Receptor Gamma, Coactivator 1 Beta Genes and Their Association with Egg Production Traits in Local Chinese Dagu Hens

Adrenergic, alpha-1B-, receptor (ADRA1B) and peroxisome proliferator-activated receptor gamma, coactivator 1 beta (PPARGC1B) genes are involved in regulation of hen ovarian development. In this study, these two genes were investigated as possible molecular markers associated with hen-housed egg production, egg weight (EW) and body weight in Chinese Dagu hens. Samples were analyzed using the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique, followed by sequencing analysis. Two novel single nucleotide polymorphisms (SNPs) were identified within the candidate genes. Among them, an A/G transition at base position 1915 in exon 2 of ADRA1B gene and a T/C mutation at base position 6146 in the 3′-untranslated region (UTR) of PPARGC1B gene were found to be polymorphic and named SNP A1915G and T6146C, respectively. The SNP A1915G (ADRA1B) leads to a non-synonymous substitution (aspartic acid 489-to-glycine). The 360 birds from the Dagu population were divided into genotypes AA and AG, allele A was found to be present at a higher frequency. Furthermore, the AG genotype correlated with significantly higher hen-housed egg production (HHEP) at 30, 43, 57, and 66 wks of age and with a higher EW at 30 and 43 wks (p<0.05). For the SNP T6146C (PPARGC1B), the hens were typed into TT and TC genotypes, with the T allele shown to be dominant. The TC genotype was also markedly correlated with higher HHEP at 57 and 66 wks of age and EW at 30 and 43 wks (p<0.05). Moreover, four haplotypes were reconstructed based on these two SNPs, with the AGTC haplotype found to be associated with the highest HHEP at 30 to 66 wks of age and with higher EW at 30 and 43 wks (p<0.05). Collectively, the two SNPs identified in this study might be used as potential genetic molecular markers favorable in the improvement of egg productivity in chicken breeding.