Molecular Cloning, Characterization, Tissue‐Specific Transcription, and Nutritional Regulation of <i>FADS</i> Genes by Dietary Curcumin in Chicken, <i>Gallus gallus</i>

In this study, five FADS genes-FADS1a, FADS1b, FADS1c, FADS2, and FADS6-were cloned and characterized in chickens. Their nutritional regulations by diets containing various levels (100, 200, 300, and 400 mg/kg) of curcumin (Curcuma longa) were also determined. We aimed to determine the functions of FADS genes in fatty acid (FA) metabolism in chickens. We identified two critical conserved regions in chicken FADS: DWXXGH and GEXA, likely conferring structural stability to the iron-binding center and modulating the electrostatic potential. The chicken FADS genes are orthologs of vertebrate FADS genes. FADS1a/FADS1b and FADS1c exhibited markedly different tissue-specific transcription. However, FADS1a, FADS1b, and FADS1c responded differently to dietary curcumin, suggesting their functional divergence. Therefore, we propose that FADS1a, FADS1b, and FADS1c were retained in the chicken genome due to neo- or sub-functionalization. Dietary curcumin upregulated four of five chicken FADS genes (except FADS1a), indicating its effect on FA metabolism in chickens. Analyzing the promoter regions of FADS1 genes is essential for identifying their regulatory mechanisms, which may explain their evolutionary fates and functions.