Identification of potential candidate genes and regulatory pathways related to reproductive capacity in hypothalamus and pituitarium of male ducks (Anas platyrhynchos) by differential transcriptome analysis

The potential genes identified in our study can serve as candidate genes for further exploration of selectable markers in ducks to improve their reproductive performance. The identified relevant biological pathways may provide an insight into the potential molecular mechanisms by which the neuroendocrine system regulates reproductive abilities in male ducks. The improvement of reproductive capacity of poultry is important for the poultry industry. The existing studies on reproductive capacity mainly focus on the testis tissue, but few reports on regulationary effect of brain neuroendocrime on reproductive capacity have been available. The hypothalamus-pituitarium-gonad (HPG) axis is an important pathway regulating spermatogenesis and sexual behavior. This study analyzed the gene expression in the hypothalamus and pituitary tissues of male ducks in high-semen-quality group (DH), low-semen-quality group (DL), and non-response group (DN) by RNA-sequencing. A total of 1980 differentially expressed genes (DEGs) were identified, and significantly less DEGs were found in pituitary gland than in hypothalamus. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that these DEGs were mainly enriched in nerve-related and synapse-related biological processes, mitochondrial inner membrane formation pathway, and ribosome structure pathway. Notably, the neuroactive ligand-receptor interaction pathway significantly enriched in all three comparisons (DH vs. DL, DH vs. DN, and DL vs. DN) was related to different reproductive performance such as semen quality and sexual response. Furthermore, six genes, including POMC, CPLX2, HAPLN2, EGR4, TOX3, and MSH4, were identified as candidate genes regulating reproductive capacity. Our findings provide new insights into the regulation mechanisms underlying the reproductive performance of male poultry, and offer a valuable reference for duck breeding programs aimed at promoting reproductive capacity. Lay Summary Individual reproductive capacity is crucial to poultry breeding and reproduction. The hypothalamus-pituitarium-gonad (HPG) axis is an important pathway regulating animal spermatogenesis and sexual behavior. This study identified the neuroactive ligand-receptor interaction pathway as the potential biological pathway regulating the semen quality and sexual behavior by differential transcriptome analysis of the hypothalamus and pituitarium of male ducks. Genes including proopiomelanocortin (POMC), complexin 2 (CPLX2), hyaluronan and proteoglycan link protein 2 (HAPLN2), early growth response 4 (EGR4), tox high mobility group box family member 3 (TOX3), and muts homolog 4 (MSH4) were identified as key candidate genes affecting the HPG axis. Our findings provide new insights into the regulatory mechanisms underlying reproductive performance in male poultry and offer a reference for breeding programs aimed to improve reproductive performance in ducks.

Automated summary

The neuroactive ligand-receptor interaction pathway was identified as a potential biological pathway regulating reproductive performance in male ducks. Six genes, including HAPLN2 and EGR4, were identified as candidate genes affecting reproductive capacity. These findings are important for improving the reproductive performance in poultry.