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