Identification and analysis of serum reproductive hormones and genes related to laying in hypothalamus of Shaoxing Ducks

【Objective】The purpose of the study was to compare the levles of reproductive hormone in serum of laying and pre-laying Shaoxing Ducks and to screen the candidate genes related to laying traits in the hypothalamic tissue, so as to provide a theoretical basis for use of molecular markers for the selection of laying performance of ducks.【Method】 The 105-day-old and 128-day-old laying and pre-laying Shaoxing Ducks were selected as the research subjects. The concentrations of estrogen(E₂),follicle stimulating hormone(FSH)and luteinizing hormone(LH)in serum were determined by radioimmunoassay(RIA). Differentially expressed genes(DEGs)of 105-day-old laying and pre-laying Shaoxing Ducks in the hypothalamus tissues were screened by transcriptome sequencing. GO functional annotation and KEGG signaling pathway enrichment analysis were performed on DEGs through GO and KEGG databases,and the accuracy of transcriptome data was verified by real-time fluorescence quantitative PCR.【Result】 At 105-day-old and 128-day-old,the concentrations of E₂ in the serum of laying Shaoxing Ducks were extremely significantly higher than those of pre-laying Shaoxing Ducks(P<0.01,the same below),and the concentrations of LH in the serum of laying Shaoxing Ducks were significantly lower than those of pre-laying Shaoxing Ducks(P<0.05,the same below). At 128-day-old,the concentrations of FSH in the serum of laying Shaoxing Ducks were significantly lower than those of pre-laying Shaoxing Ducks. Based on transcriptome sequencing,a total of 617 DEGs were screened from the hypothalamic tissues of 105-day-old laying and pre-laying Shaoxing Ducks,among which 91 DEGs were up-regulated and 526 were down-regulated. GO functional annotation analysis showed that DEGs were mainly annotated on functional entries such as nervous system development, hormone activity and cell migration. KEGG signaling pathway enrichment analysis revealed that neuroactive ligandreceptor interaction and endocytosis may be signaling pathways related to precocious performance. The results of real-time fluorescence quantitative PCR showed that the relative expressions of NPY,ITIH2 and GDF10 genes in the hypothalamus of laying Shaoxing Ducks were extremely significantly up-regulated compared with those of pre-laying Shaoxing Ducks, and the relative espressions of WIF1,HSP70 and Ret genes in the laying Shaoxing Ducks were extremely significantly down-regulated than those of pre-laying Shaoxing Ducks,whereas there was no significant difference in the relative expression of FASN gene(P>0.05), which were basically consistent with the transcriptome sequencing results.【Conclusion】 The DEGs such as NPY,GnIH, TRH and HSP70 screened from the hypothalamus of Shaoxing Ducks act on the hypothalamus-pituitary-gonadal axis through signaling pathways such as neuroactive ligand-receptor interaction and endocytosis, and affect the secretion and release of reproductive hormones such as E₂, FSH and LH, and then regulate the time of laying in Shaoxing Ducks.