Innovation, conservation, and the function of embryonic head and brain patterning genes in the diversification of head morphologies in Onthophagus and Tribolium beetles.

ZATTARA, E.E.; LINZ, M.D.; TOMOYASU, Y.; MOCZEK, A.P.

Berkeley, CA

Conferencia; Pan-American Society for Evolutionary Developmental Biology 2015 Inaugural Meeting; 2015

Pan-American Society for Evolutionary Developmental Biology

How the insect head ispatterned is a long-standing question. Several studies focusing on anterior homeoboxgenes have increased our understanding of ventral head patterning, but the dorsalhead is mostly terra incognita. Yet evolutionof novel structures and changes in relative sizes of dorsal head regions haveplayed critical roles in insect diversification. Furthermore, while moststudies have addressed embryonic head patterning genes, virtually nothing isknown about how the dorsal head is patterned during post-embryonic development.To close this gap, we used larval RNAi to investigate the roles of the embryonichead and brain patterning genes orthodenticleand six3/optix in instructing dorsalhead formation in adults of the flour beetle Tribolium castaneum and the highly morphologically divergent hornedbeetles Onthophagus taurus and O. sagittarius. We show that in Tribolium, otd1 and otd1+otd2 RNAiadults present subtle gaps in ventral trunk plates but otherwise lack obvious phenotypiceffects in the dorsal head. In contrast, otd1and otd1+otd2 RNAi in Onthophagus horned beetles results indeletion of large portions of ventral trunk plates, and spectacular changes indorsal head structures, including massive reduction or deletion of horns, novelpatterns of horn formation, and ectopic medial eye development. First data on six3/optix suggest different but complementaryeffects during adult head patterning. Collectively, our results suggest that embryonichead and brain patterning genes play crucial and previously undescribed rolesin specifying the identity of medial epidermal structures during postembryonicdevelopment.