Data from: High-density lipoprotein receptor SCARB1 is required for carotenoid coloration in birds

Yellow, orange, and red coloration is a fundamental aspect of avian diversity and serves as an important signal in mate choice and aggressive interactions. This coloration is often produced through the deposition of diet-derived carotenoid pigments, yet the mechanisms of carotenoid uptake and transport are not well-understood. The white recessive breed of the common canary (Serinus canaria), which carries an autosomal recessive mutation that renders its plumage pure white, provides a unique opportunity to investigate mechanisms of carotenoid coloration. We carried out detailed genomic and biochemical analyses comparing the white recessive with yellow and red breeds of canaries. Biochemical analysis revealed that carotenoids are absent or at very low concentrations in feathers and several tissues of white recessive canaries, consistent with a genetic defect in carotenoid uptake. Using a combination of genetic mapping approaches, we show that the white recessive allele is due to a splice donor site mutation in the scavenger receptor B1 (SCARB1; also known as SR-B1) gene. This mutation results in abnormal splicing, with the most abundant transcript lacking exon 4. Through functional assays, we further demonstrate that wild-type SCARB1 promotes cellular uptake of carotenoids but that this function is lost in the predominant mutant isoform in white recessive canaries. Our results indicate that SCARB1 is an essential mediator of the expression of carotenoid-based coloration in birds, and suggest a potential link between visual displays and lipid metabolism.黄、橙、红羽色是鸟类多样性的核心特征之一，同时也是配偶选择与攻击性互动中的重要信号。这类羽色通常通过沉积膳食来源的类胡萝卜素（carotenoid）色素生成，但目前学界对类胡萝卜素摄取与转运的机制仍知之甚少。携带常染色体隐性突变、羽毛呈纯白色的普通金丝雀（Serinus canaria）隐性白羽品系，为研究类胡萝卜素羽色的形成机制提供了独特的研究模型。本研究针对金丝雀的隐性白羽品系与黄羽、红羽品系开展了详细的基因组与生化分析。生化分析结果显示，隐性白羽金丝雀的羽毛与多种组织中均不含类胡萝卜素，或仅含极微量的类胡萝卜素，这与类胡萝卜素摄取环节存在遗传缺陷的推测相符。通过联合运用多种遗传定位手段，本研究证实隐性白羽等位基因源于清道夫受体B1（scavenger receptor B1, SCARB1，亦称SR-B1）基因的剪接供体位点突变。该突变会导致异常剪接，其中丰度最高的转录本缺失第4号外显子。通过功能实验，本研究进一步证实：野生型SCARB1可促进细胞摄取类胡萝卜素，但隐性白羽金丝雀中占主导的突变型SCARB1则丧失了这一功能。本研究结果表明，SCARB1是鸟类类胡萝卜素依赖型羽色表达的关键介导因子，同时也提示视觉展示与脂质代谢之间存在潜在关联。