Purpose To explore the molecular characteristics, tissue expression patterns, and the 24 bp insertion/deletion polymorphism in the promoter region of prolactin (PRL) gene in Wuding chicken, and to analyze its association with broodiness.
Methods Using the pituitary gland of Wuding chicken as research material, the coding sequence (CDS) of PRL gene was cloned by reverse transcription polymerase chain reaction technology, and the structure and function of its encoded product were analyzed by bioinformatics methods. The expression differences of PRL gene in pituitary and ovarian tissues of Wuding chicken during the laying and brooding periods were detected by real-time fluorescence quantitative polymerase chain reaction. The 24 bp insertion/deletion polymorphism in the promoter region of PRL gene was detected, using Jingfen No.2 egg chicken as a control, and the association between the polymorphism and broodiness was analyzed.
Results The CDS of PRL gene in Wuding chicken was 690 bp, encoding 229 amino acids. PRL protein was a hydrophilic protein containing a conserved prolactin-like protein family domain, which lacked a transmembrane structure, but had a signal peptide, and primarily exerted its effects extracellularly. GO and protein interaction analysis showed that PRL protein activated downstream signaling pathways by binding to prolactin receptor, participated in biological processes such as cell proliferation, and might indirectly affect luteinizing hormone secretion by inhibiting the release of gonadotropin-releasing hormone. The tissue expression analysis showed that PRL gene was expressed in both pituitary and ovary, with significantly higher expression during the brooding period than during the laying period. The polymorphism detection showed that the genotype frequencies of the 24 bp insertion/deletion in PRL gene promoter region in Wuding chickens were as follows: type II was 0.00%, type ID was 15.63%, and type DD was 84.37%. The association analysis showed that there was an extremely significant correlation between the 24 bp insertion/deletion polymorphism in PRL gene promoter region and broodiness in Wuding chicken, which might affect the expression level of PRL gene, thereby affecting the broodiness of Wuding chicken.
Conclusion The PRL gene plays an important role in the pituitary and ovary of Wuding chicken, and it may affect the broodiness behavior through the 24 bp insertion/deletion polymorphism in the promoter region.
DownLoad: