Polymorphism analysis and expression profile of the estrogen receptor 2 gene in Leizhou black duck

Research Note: Polymorphisms of gonadotrophin-releasing hormone gene and their association with growth traits in quail (Coturnix Coturnix)

This study aimed to identify polymorphisms of gonadotropin-releasing hormone (GnRH) gene and their association with growth traits in quail by PCR and direct sequencing. Genomic DNA was extracted from quail blood samples of 36 from Savimalt (SV) and 49 from French Giant (FG). Growth traits were measured and used for candidate gene analysis, as body weight (BW), shank length (SL), chest width (CW), chest depth (CD), breastbone length (BBL), body length (BL), and shank circumference (SC). The results showed that a total of 20 SNPs were detected in GnRH gene, whereas 8 SNPs were significantly associated with growth traits (P < 0.05). The T215C, G279A, C458T, A520G, and C547G were significantly associated with SL at 3 wk of age in the FG strain, whereas A583T was significantly related to BBL and BL, and C591T was significantly related to SL, BBL, and BL, whereas A592G was significantly correlated with SL, CW, CD, BBL, and BL (P < 0.05). The 8 SNPs were significantly related to CW, CD, and BBL at 3 wk of age in the SV strain, whereas A583T, C591T, and A592G were significantly associated with BW (P < 0.05). The G279A showed significant correlations with SL at 5 wk of age in FG, whereas A583T showed significant associations with SC in FG, and C591T was significantly associated with BW and SC in FG, whereas A592T was significantly related to BW, SL, and CD in FG (P < 0.05). The T215C, G279A, C458T, A520G, and C547G were significantly correlated with BW, CW, BBL, and BL at 5 wk of age in SV, whereas A583T, C591T, and A592G were significantly related to BW, SL, CW, BBL, and BL (P < 0.05). Haplotypes based on 8 SNPs showed significant correlation with BW, SL, CW, CD, BBL, BL, and SC in FG (P < 0.05). In conclusion, the GnRH gene could be used as a molecular genetic marker to provide theoretical foundation to improve growth traits in quail.

TAT gene polymorphism and its relationship with production traits in Muscovy ducks (Cairina Moschata)

In a previous study, the laying pattern of Muscovy duck was explored by macro-fitting the laying curve of Muscovy duck, and transcriptome sequencing technique of the ovarian tissues was used to screen the egg-related gene "TAT." Moreover, recent results have shown that TAT is expressed in organs such as oviduct, ovary, and testis. The objective of this study is to examine the effect of TAT gene on egg production traits of Muscovy ducks. First, the expression levels of TAT gene in highest producing (HP) and lowest producing (LP) in 3 tissues related to reproduction were examined, and the results indicated that the expression of TAT gene in hypothalamus was significantly different between HP and LP groups. Then, 6 SNP loci (g. 120G>T, g, 122G>A, g, 254G> A, g. 270C >T, g, 312G>A, and g. 341C>A) were detected in TAT gene. Further, association analysis between the six SNP loci of TAT gene and egg production traits of 652 individual Muscovy ducks was done. The results showed that g. 254G>A and g. 270C>T were significantly correlated (P < 0.05 or 0.001) with the egg production traits of Muscovy ducks. This study elucidated the molecular mechanism that TAT gene might be regulating the egg production traits of Muscovy ducks.

Genetic resilience in chickens against bacterial, viral and protozoal pathogens

The genome contributes to the uniqueness of an individual breed, and enables distinctive characteristics to be passed from one generation to the next. The allelic heterogeneity of a certain breed results in a different response to a pathogen with different genomic expression. Disease resistance in chicken is a polygenic trait that involves different genes that confer resistance against pathogens. Such resistance also involves major histocompatibility (MHC) molecules, immunoglobulins, cytokines, interleukins, T and B cells, and CD4+ and CD8+ T lymphocytes, which are involved in host protection. The MHC is associated with antigen presentation, antibody production, and cytokine stimulation, which highlight its role in disease resistance. The natural resistance-associated macrophage protein 1 (Nramp-1), interferon (IFN), myxovirus-resistance gene, myeloid differentiation primary response 88 (MyD88), receptor-interacting serine/threonine kinase 2 (RIP2), and heterophile cells are involved in disease resistance and susceptibility of chicken. Studies related to disease resistance genetics, epigenetics, and quantitative trait loci would enable the identification of resistance markers and the development of disease resistance breeds. Microbial infections are responsible for significant outbreaks and have blighted the poultry industry. Breeding disease-resistant chicken strains may be helpful in tackling pathogens and increasing the current understanding on host genetics in the fight against communicable diseases. Advanced technologies, such as the CRISPR/Cas9 system, whole genome sequencing, RNA sequencing, and high-density single nucleotide polymorphism (SNP) genotyping, aid the development of resistant breeds, which would significantly decrease the use of antibiotics and vaccination in poultry. In this review, we aimed to reveal the recent genetic basis of infection and genomic modification that increase resistance against different pathogens in chickens.

The study of candidate genes in the improvement of egg production in ducks – a review

Duck is the second-largest poultry species aside from chicken. The rate of egg production is a major determinant of the economic income of poultry farmers. Among the reproductive organs, the ovary is a major part of the female reproductive system which is highly important for egg production. Based on the importance of this organ, several studies have been carried out to identify candidate genes at the transcriptome level, and also the expression level of these genes at different tissues or egg-laying conditions, and single nucleotide polymorphism (SNPs) of genes associated with egg production in duck. In this review, expression profile and association study analyses at SNPs level of different candidate genes with egg production traits of duck were highlighted. Furthermore, different studies on transcriptome analysis, Quantitative Trait Loci (QTL) mapping, and Genome Wide Association Study (GWAS) approach used to identify potential candidate genes for egg production in ducks were reported. This review would widen our knowledge on molecular markers that are associated or have a positive correlation to improving egg production in ducks, for the increasing world populace.