Data from: Genetic basis of stage-specific melanism: a putative role for a cysteine sulfinic acid decarboxylase in insect pigmentation

Melanism, the overall darkening of the body, is a widespread form of animal adaptation to particular environments, and includes bookcase examples of evolution by natural selection, such as industrial melanism in the peppered moth. The major components of the melanin biosynthesis pathway have been characterized in model insects, but little is known about the genetic basis of life-stage specific melanism such as cases described in some lepidopteran species. Here, we investigate two melanic mutations of Bicyclus anynana butterflies, called Chocolate and melanine, that exclusively affect pigmentation of the larval and adult stages, respectively. Our analysis of Mendelian segregation patterns reveals that the larval and adult melanic phenotypes are due to alleles at different, independently segregating loci. Our linkage mapping analysis excludes the pigmentation candidate gene black as the melanine locus, and implicates the gene encoding a putative PLP-dependant cysteine sulfinic acid decarboxylase as the Chocolate locus. We show variation in coding sequence and in expression levels for this candidate larval melanism locus. This is the first study that suggests a biological function for this gene in insects. Our findings open up exciting opportunities to study the role of this locus in the evolution of adaptive variation in pigmentation, and the uncoupling of regulation of pigment biosynthesis across developmental stages with different ecologies and pressures on body coloration.黑化（melanism）指整体体色加深的现象，是动物适应特定环境的普遍演化策略之一，包含诸多自然选择驱动演化的经典案例，例如桦尺蠖（peppered moth）的工业黑化现象。模式昆虫中黑色素生物合成通路的核心组分已得到系统解析，但针对鳞翅目（lepidopteran）部分物种所报道的、发育阶段特异性黑化现象的遗传基础，目前仍鲜有研究。本研究以安那眼蝶（Bicyclus anynana）的两种黑化突变体——Chocolate与melanine为研究对象，二者分别仅影响幼虫与成虫阶段的色素沉着。我们对孟德尔分离模式的分析显示，幼虫与成虫的黑化表型分别由位于不同且独立分离基因座（locus）上的等位基因所调控。本研究的连锁作图（linkage mapping）分析排除了色素沉着候选基因black作为melanine基因座的可能性，并指出编码假定磷酸吡哆醛（PLP）依赖性半胱氨酸亚磺酸脱羧酶的基因为Chocolate基因座的候选基因。我们发现该幼虫黑化候选基因座的编码序列与表达水平均存在遗传变异。本研究首次揭示了该基因在昆虫体内的生物学功能。本研究结果为探索该基因座在体色适应性变异演化中的作用，以及解析不同生态环境与体色选择压力下跨发育阶段色素生物合成调控的解耦机制提供了重要研究契机。