A mutation in the promoter of the chicken β,β-carotene 15,15'-monooxygenase 1 gene alters xanthophyll metabolism through a selective effect on its mRNA abundance in the breast muscle.

A polymorphism in the promoter of the β,β-carotene 15,15'-monooxygenase 1 (BCMO1) gene recently was identified in an experimental cross between 2 chicken lines divergently selected on growth rate and found to be associated with variations in the yellow color of the breast meat. In this study, the effects of the polymorphism on several aspects of carotenoid metabolism were evaluated in chickens sharing the same genetic background except for their genotype at the BCMO1 locus. We confirmed that BCMO1 mRNA abundance varied (P < 0.001) between the 2 homozygous genotypes (GG << AA) and in the pectoralis major muscle. By contrast, BCMO1 mRNA expression was not affected (P > 0.05) by the polymorphism in the duodenum, liver, or sartorius muscle. The breast meat of GG chickens was more (P < 0.001) yellow and richer in lutein (P < 0.01) and zeaxanthin (P < 0.05) compared to that of AA chickens whereas these variables did not differ (P > 0.05) in the other tissues tested. The GG were also characterized by reduced (P < 0.01) plasma lutein and zeaxanthin concentrations than AA without affecting plasma and tissue content of fat-soluble vitamins A and E. As lutein and zeaxanthin are usually not considered as substrates of the BCMO1 enzyme, the impact of BCMO1 polymorphism on the activity of other genes involved in carotenoid transport (SCARB1 and CD36 encoding the scavenger receptor class B type I and the cluster determinant 36, respectively) and metabolism (BCDO2 encoding β,β-carotene 9',10'-dioxygenase 2) was evaluated. The BCMO1 polymorphism did not affect mRNA abundance of BCDO2, SCARB1, or CD36, regardless of tissue considered. Taken together, these results indicated that a genetic variant of BCMO1 specifically changes lutein and zeaxanthin content in the chicken plasma and breast muscle without impairing vitamin A and E metabolism.