TRPA1 for Butterfly Eyespot Formation

Butterfly wing color pattern formation is a process of two-dimensional morphogenesis involving long-range lateral signaling in pupal wing tissues. We hypothesized that TRP (transient receptor potential) channels, which are multimodal sensors for various stimuli, are involved in this developmental process. Using the blue pansy butterfly <i>Junonia orithya</i>, we injected the TRPA1 antagonists, AM0902 and AP-18, and an agonist, JT010, into pupae and observed that the eyespot core disk area in adult wings increased and decreased in response to AM0902 and JT010, respectively, although AP-18 did not induce any change. Furthermore, the eyespot outer black ring area increased in response to AM0902, and the orange ring area increased in response to JT010. We detected TRPA1 mRNA via RT-PCR in the pupal wing tissues of this species. An antibody against the <i>J. orithya</i> TRPA1 extracellular site induced unique aberrant color patterns with wing vein defects. These results suggest that TRPA1 is expressed in pupal wing tissue and may integrate signaling information to determine eyespot size and structure in butterfly wings. TRPA1 likely suppresses the black core disk and the outer black ring and enhances the nonblack orange ring in eyespots during development.