Abstracts (first author)
Evolutionary “tinkering” in the origin of the insect terminal patterning system
A key early process in development is the determination of the embryonic axes. The anterior-posterior axis in insects is determined by a series of signaling pathways and transcription factors. These are best known from the fruitfly Drosophila melanogaster, where the torso pathway activates a number of posterior transcription factors, while interacting diffusible factors define the anterior. We have cloned the homologues of most of the key players in terminal patterning from the milkweed bug Oncopeltus fasciatus, focusing on huckebein, torsolike, hunchback, orthodenticle and tailless. We then studied their expression and function, and their interaction with other early developmental pathways. Our results show that many of the pathways known to be involved in Drosophila terminal patterning have different roles in Oncopeltus development. We suggest that their roles in Drosophila are derived from the more ancestral roles still preserved in Oncopeltus. We use our results to discuss a model for the evolution of the terminal patterning system in insects, and show that the evolution of this pathway is a classic example of evolutionary "tinkering", where different elements are co-opted independently into a single novel patterning system.