Identification of the BCO gene family and its effect on body coloration in Lutjanus erythropterus.

The beta-carotene oxygenase (BCO) gene family plays a key role in carotenoid metabolism, which is closely linked to body color formation in teleosts. However, its function in Lutjanus erythropterus remains unclear. Here, we identified four BCO gene family members in the genome and characterized their evolutionary conservation, tissue-specific expression, and potential roles in pigmentation. Tissue expression profiling revealed high expression of all BCO genes in the heart, with Bco1, Bco1l, and Bco2l also highly expressed in the intestine and liver. Developmental stage analysis showed that Bco1 maintained relatively high expression around hatching, and all genes peaked at 3 days post‑hatching (dph). In differently colored skin at 45 dph, Bco1 showed the highest expression in white skin, whereas Bco2b expression in black skin was approximately twice that in yellow and white skin. Astaxanthin feeding upregulated BCO expression in multiple tissues. Under different background culture conditions, Bco1 and Bco2b exhibited similar expression patterns, which followed a trend similar to total carotenoid content. These findings indicate a correlation between BCO gene expression and the body color of L. erythropterus, suggesting that these genes may serve as candidate genes potentially involved in body color formation in this species.