Polycomb group proteins confer robustness to aposematic coloration in the milkweed bug, <i>Oncopeltus fasciatus</i>

Aposematic coloration offers an opportunity to explore the molecular mechanisms underlying canalization. In this study, the role of epigenetic regulation underlying robustness was explored in the aposematic coloration of the milkweed bug, <i>Oncopeltus fasciatus. Polycomb</i> (<i>Pc</i>) and <i>Enhancer of zeste</i> (<i>E(z)</i>), which encode components of the Polycomb repressive complex 1 (PRC1) and PRC2, respectively, and <i>jing</i>, which encodes a component of the PRC2.2 subcomplex, were knocked down in the fourth instar of <i>O. fasciatus</i>. Knockdown of these genes led to alterations in scutellar morphology and melanization. In particular, when <i>Pc</i> was knocked down, the adults developed a highly melanized abdomen, head and forewings at all temperatures examined. In contrast, the <i>E(z)</i> and <i>jing</i> knockdown led to increased plasticity of the dorsal forewing melanization across different temperatures. Moreover, <i>jing</i> knockdown adults exhibited increased plasticity in the dorsal melanization of the head and the thorax. These observations demonstrate that histone modifiers may play a key role during the process of canalization to confer robustness in the aposematic coloration.