Molecular basis of the wing coloration in a Batesian mimic butterfly, Papilio polytes.. Papilio polytes

Batesian mimicry protects an animal from predators by resembling distasteful models in shape, color pattern, or behavior. To elucidate the mechanisms of wing coloration involved in the mimicry, we investigated the chemical properties and gene expression for the pale yellow and red pigments of a swallowtail butterfly, Papilio polytes, the females of which mimics the unpalatable butterfly Pachiliopta aristolochiae. Using LC/MS and RT-PCR analyses, we showed the pale yellow region of non-mimetic female was composed of kynurenine and N--alanyldopamine (NBAD), but the pigment was absent in the similarly colored region of the mimetic female. Comprehensive RNA-sequencing analysis showed that kynurenine/NBAD synthesis and Toll signaling pathway genes were up-regulated in the red spots peculiar to mimetic female wings. These results demonstrate that drastic changes of gene networks not only in red but also pale yellow regions can switch wing color patterns between non-mimetic and mimetic female.

贝氏拟态（Batesian mimicry）指动物通过在外形、色彩图案或行为上模拟令捕食者厌恶的模型物种，从而躲避天敌的防御策略。为阐明拟态相关的翅膀色彩形成机制，我们针对凤蝶（swallowtail butterfly）玉带凤蝶（Papilio polytes）的淡黄色与红色色素开展了化学性质及基因表达分析；该物种的雌性个体能够模拟难食性蝴蝶Pachiliopta aristolochiae。通过液相色谱-质谱联用（LC/MS）与逆转录聚合酶链式反应（RT-PCR）分析，我们发现非拟态雌性个体的淡黄色区域含有犬尿氨酸（kynurenine）与N-β-丙氨酰多巴胺（N-β-alanyldopamine, NBAD），而拟态雌性个体的同色区域中并无此类色素。全面的RNA测序（RNA-sequencing）分析显示，犬尿氨酸/NBAD合成通路及Toll信号通路（Toll signaling pathway）基因在拟态雌性翅膀特有的红色斑点中显著上调。上述结果表明，不仅红色区域，淡黄色区域的基因网络均发生了剧烈改变，从而实现非拟态与拟态雌性个体间翅膀色彩图案的转换。