Expression of SCARB1 in feather follicles is necessary but not sufficient for carotenoid-based feather pigmentation in Gouldian finches

Marques, Cristiana I. and Fekete, Csaba and Afonso, Sandra and Maršík, Petr and Araújo, Pedro M. and Carneiro, Miguel (2026) Expression of SCARB1 in feather follicles is necessary but not sufficient for carotenoid-based feather pigmentation in Gouldian finches. BIOLOGY LETTERS, 22 (3). ISSN 1744-9561 (print); 1744-957X (online)

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Abstract

Carotenoids play fundamental roles in avian ecology and evolution. Full expression of carotenoid-based plumage relies on key molecular mechanisms that regulate the uptake, processing and deposition of dietary pigments into target tissues. The blue Gouldian finch (Erythrura gouldiae) variety is explained by an autosomal recessive locus that affects carotenoid coloration. Using whole-genome sequencing data and genetic mapping, we identified a splice-acceptor mutation in scavenger receptor B1 (SCARB1) that abolishes carotenoid-based pigmentation. Biochemical analyses revealed that blue individuals circulate extremely low concentrations of dietary carotenoids, confirming a genetic disruption of carotenoid uptake and transport in the gut. Through genotyping of the candidate causative mutation in carotenoid-containing and carotenoid-free mask feathers of a mosaic blue individual, we further demonstrate that somatic reversion of blue rescues SCARB1 function and locally restores carotenoid deposition in feathers. Finally, by comparing the transcriptomes of carotenoid-containing and carotenoid-free feather follicles from different plumage regions of wild-type birds, we show that SCARB1 expression alone is not sufficient to trigger carotenoid pigmentation. These findings reinforce the role of SCARB1 as a key facilitator of carotenoid uptake and transport in the gut, while also establishing its necessity for localized uptake of carotenoids to developing feather follicles.

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