Transcriptomic insights into the effects of tyrosine on sub-Columbian plumage in H line chickens

Tyrosine is known to influence melanin generation; however, its involvement in melanin production in chicken feathers is unknown. We evaluated the feather color of H-line chickens fed diets containing different concentrations of tyrosine (0, 0.4, 0.6, 0.8, and 1.0%). The results indicated that a diet containing 1.0% tyrosine fed for 40 days significantly increased melanin deposition in the feathers (p < 0.05). Following this observation, we collected feather follicle tissue from chickens fed either 0% or 1.0% tyrosine at the 40-day time point for transcriptome sequencing. RNA-seq analysis identified a total of 314 DEGs, comprising 116 upregulated and 198 downregulated genes. KEGG analysis of feather follicle tissue revealed that 7 DEGs (EDNRB2, WNT3, POMC, INS, FLT3, CACNA2D3, and CACNA1I) mapped to melanin-related pathways, including the melanogenesis, MAPK signaling and Wnt signaling pathways. We also identified specific protein interactions within the melanin pathway, including EDNRB2-MLPH and WNT3-FGF16 interactions. Notably, the expression level of the EDNRB2 gene reached its peak at 10 weeks within the 0-12 week growth period in H-line chickens. In primary chicken melanocytes, EDNRB2 expression was quantified following tyrosine supplementation and was found to be markedly elevated at a concentration of 10^-6 mol/L, significantly higher than the control and other treatment groups (p < 0.05). Overall, our findings suggest the significant involvement of the tyrosine-induced EDNRB2 regulatory network in melanin levels in sub-Columbian plumage. Taken together, these findings increase our understanding of the molecular mechanisms that regulate tyrosine-mediated melanin deposition in chicken plumage.