Her seminar begins at 4:10 p.m. The Zoom link is https://ucdavis.zoom.us/j/99515291076. The host is doctoral candidate Xavier Zahnle of the Jason Bond lab, UC Davis Department of Entomology and Nematology.
"I use arthropod appendages as a model to understand how ancient structures like gills and legs evolve and innovate over hundreds of millions of years," Bruce writes in her abstract. "My work suggests that many unexpected structures, such as the insect wing and the crustacean carapace, are derived from a shared ancestral structure. This has deep implications for how we assume genetic networks evolve over vast phylogenetic distances: rather than repeated co-option events, my work suggests that genetic networks are more ancient, more evolvable, and more predictable than currently thought."
A native of the San Francisco Bay area, Heather moved with her family to Cornville, Ariz., at age 12. She holds an associate of arts degree in biological sciences (2006) from Yavapai College, Prescott, Ariz., and a bachelor's degree in cell/cellular and molecular biology (2010) from the University of Arizona. She received her doctorate in cell/cellular and molecular biology from UC Berkeley in 2017.
Bruce authored Insect Wings and Body Wall Evolved from Ancient Leg Segments, published in bioRxiv in January 2018. She wrote: "Researchers have long debated the origin of insect wings. One theory proposes that the proximal portion of the ancestral crustacean leg became incorporated into the body, which moved the leg's epipod (multi-functional lobe, e.g. gill) dorsally, up onto the back to form insect wings. Another theory proposes that the dorsal insect body wall co-opted crustacean epipod genes to form wings. Alternatively, wings may be derived from both leg and body wall (dual origin). To determine whether wings can be traced to ancestral, pre-insect structures, or arose by co-option, comparisons are necessary between insects and arthropods more representative of the ancestral state, where the hypothesized proximal leg region is not fused to the body wall."
"To do so," she continued, "we examined the function of five leg gap genes in the crustacean Parhyale hawaiensis and compared this to previous functional data from insects. Here we show, using CRISPR-Cas9 mutagenesis, that leg segment deletion phenotypes of all five leg gap genes in Parhyale align to those of insects only by including the hypothesized fused ancestral proximal leg region. We also argue that possession of eight leg segments is the ancestral state for crustaceans. Thus, Parhyale incorporated one leg segment into the body, which now bears the tergal plate, while insects incorporated two leg segments into the body, the most proximal one bearing the wing. We propose a model wherein much of the body wall of insects, including the entire wing, is derived from these two ancestral proximal leg segments, giving the appearance of a dual origin. This model explains many observations in favor of either the body wall, epipod, or dual origin of insect wings."
As a research scientist, Bruce led an independent research project from 2018-2018 in the San Francisco Bay Area where "I integrated CRISPR-Cas9 data with previous research spanning 130 years and several disciplines to demonstrate that all arthropods use the same leg patterning system, and that insect wings evolved from crustacean gills."
Nematologist Shahid Siddique, assistant professor, UC Davis Department of Entomology and Nematology, is coordinating the spring seminars. For Zoom technical issues, contact him at ssiddique@ucdavis.edu.