Data from: Genetic basis for red coloration in birds

The yellow and red feather pigmentation of many bird species [1] plays pivotal roles in social signaling and mate choice [2, 3]. To produce red pigments, birds ingest yellow carotenoids and endogenously convert them into red ketocarotenoids via an oxidation reaction catalyzed by a previously unknown ketolase [4–6]. We investigated the genetic basis for red coloration in birds using whole-genome sequencing of red siskins (Spinus cucullata), common canaries (Serinus canaria), and ‘‘red factor’’ canaries, which are the hybrid product of crossing red siskins with common canaries [7]. We identified two genomic regions introgressed from red siskins into red factor canaries that are required for red coloration. One of these regions contains a gene encoding a cytochrome P450 enzyme, CYP2J19. Transcriptome analysis demonstrates that CYP2J19 is significantly upregulated in the skin and liver of red factor canaries, strongly implicating CYP2J19 as the ketolase that mediates red coloration in birds. Interestingly, a second introgressed region required for red feathers resides within the epidermal differentiation complex, a cluster of genes involved in development of the integument. Lastly, we present evidence that CYP2J19 is involved in ketocarotenoid formation in the retina. The discovery of the carotenoid ketolase has important implications for understanding sensory function and signaling mediated by carotenoid pigmentation.诸多鸟类的羽毛黄、红色素沉着[1]在社会信号传递与配偶选择中发挥关键作用[2,3]。为合成红色素，鸟类会摄取黄色类胡萝卜素（carotenoids），并通过一种此前未知的酮化酶（ketolase）催化的氧化反应，在体内将其转化为红色酮类类胡萝卜素（ketocarotenoids）[4-6]。本研究通过对红金翅雀（Spinus cucullata）、普通金丝雀（Serinus canaria）以及由红金翅雀与普通金丝雀杂交得到的“红因子”金丝雀[7]开展全基因组测序（whole-genome sequencing），探究了鸟类红色羽色的遗传基础。我们鉴定出两个从红金翅雀渐渗至红因子金丝雀体内、且为红色羽色形成所必需的基因组区域。其中一个区域包含一个编码细胞色素P450（cytochrome P450）酶CYP2J19的基因。转录组分析（transcriptome analysis）结果显示，CYP2J19在红因子金丝雀的皮肤与肝脏中显著上调表达，有力证明CYP2J19即为介导鸟类红色羽色形成的酮化酶。有趣的是，第二个与红色羽色形成必需的渐渗区域位于表皮分化复合体（epidermal differentiation complex）内部——该复合体是一组参与体被（integument）发育的基因簇。最后，我们提供证据表明CYP2J19参与视网膜（retina）内酮类类胡萝卜素的合成。这类类胡萝卜素酮化酶的发现，对于理解由类胡萝卜素色素沉着介导的感官功能与信号传递具有重要意义。