Transcriptome analysis reveals key genes and pathways associated with egg production in Nandan-Yao domestic chicken

Egg production is a very important economic trait in chicken breeding, but its molecular mechanism is unclear until now. Nandan-Yao chicken (Gallus gallus domesticus) is a native breed in Guangxi province, China, which is famous for good meet quality, but with low egg production.To explore the molecular regulation related to egg production, high egg production (HEP) and low egg production (LEP) were divided according to the total egg number at 55 weeks, and the concentration of serum sex hormones was tested to evaluate the physiological function of ovary and uterus. RNA sequencing (RNA-Seq) was used to explore the transcriptome from the ovary and uterus of Nandan-Yao chicken.The levels of serum sex hormone showed that concentrations of estradiol (E2), follicle-stimulating hormone (FSH), and luteotropic hormone (LH) were significantly higher in HEP than those in LEP (P < 0.01), while the concentration of testosterone (T) was significantly lower in HEP (P < 0.01). RNA-Seq analysis identified 901 and 2763 differentially expressed genes (DEGs) in ovary and uterus, respectively. Enrichment analysis showed that DEGs were significantly involved in the regulation of tight junction in the ovary (P < 0.05), while in uterus, DEGs were mainly enriched in the phagosome, ECM-receptor interaction, cell adhesion molecules (CAMs), focal adhesion, cardiac muscle contraction, cytokine-cytokine receptor interaction, and the regulation of MAPK signaling pathway (P < 0.05). Protein network interaction and function analyses revealed that FN1, FGF7, SOX2 identified from the ovary, and UQCRH, COX5A, FN1 from the uterus might be key candidate genes for egg production in Nandan-Yao chicken.Our study provided key candidate genes and pathways involved in the egg-laying process of Nandan-Yao chicken and could help to further understand the molecular mechanisms of chicken reproduction.