Post-Doctoral Researcher Cornell University Ithaca, New York, United States
The common buckeye, Junonia coenia, is a butterfly that shows seasonal wing pattern plasticity. In this species the developmental switch between the summer or autumn morph is determined by a combination of daylength and temperature cues. These environmental cues are physiologically transduced by a timing shift in a 20-hydroxyecdysone pulse during pupal development that results in either a tan or red wing color phenotype. It has been proposed that nuclear hormone receptors, transcription factors that are activated when bound to hormones, modulate the chromatin landscape to effect genome-wide shifts in gene expression to generate these alternative phenotypes. Direct evidence for this mechanism is still lacking, however. In this study we aim to assess this model by characterizing hormone receptor binding at cis-regulatory elements that show season-specific differences in chromatin accessibility. Our work focuses on regulatory elements of cortex and trehalase – two genes previously shown to control seasonal wing coloration. We are now using CRISPR-Cas9 to test the roles of specific hormone receptor binding sites that may control seasonal color patterns. This work will improve our mechanistic understanding of how external cues can be rapidly translated into genome-wide shifts in gene expression, and how insect genomes can deploy alternate developmental programs to adapt to changing environments.
