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）指生物体整体体色加深，是动物适应特定环境的一类广泛存在的适应性演化策略，亦是自然选择驱动演化的经典案例，例如桦尺蛾的工业黑化现象。模式昆虫的黑色素生物合成通路核心组分已得到充分解析，但针对部分鳞翅目物种所报道的、发育阶段特异性黑化的遗传基础，目前仍所知甚少。本研究聚焦于泽兰眼蝶（Bicyclus anynana）的两种黑化突变体——Chocolate与melanine，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不同的、独立分离的基因座等位基因所控制。连锁定位分析排除了色素沉着候选基因black作为melanine基因座的可能性，并将编码假定PLP依赖型半胱氨酸亚磺酸脱羧酶（PLP-dependant cysteine sulfinic acid decarboxylase）的基因确定为Chocolate基因座的候选靶点。我们发现该候选幼虫黑化基因座的编码序列与表达水平均存在变异。本研究是首个揭示该基因在昆虫体内生物学功能的相关报道。我们的研究结果为探索该基因座在色素沉着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，不同发育阶段间色素生物合成调控的解偶联机制，开辟了极具前景的研究方向。