This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2020, Integrative Research Investigating the Rules of Life Governing Interactions Between Genomes, Environment and Phenotypes. The fellowship supports research and training of the Fellow that will contribute to the area of Rules of Life in innovative ways. Insects that eat plants comprise the vast majority of terrestrial animal species, and most specialize on a small number of plant species. Understanding host specialization in insects is thus important for understanding the diversity of life on Earth. One hypothesis for the prevalence of host specialization is that it allows insects to incorporate toxic host plant chemicals into their own tissues. This process is known as sequestration and helps to confer chemically-mediated protection against predators and pathogens. Sequestration in insects is best-known from the monarch butterfly (Danaus plexippus), whose larvae feed on milkweed plants containing toxic chemicals (cardenolides) that make them distasteful to predators. Although monarch sequestration has been studied, the genes involved in cardenolide uptake and transport remain unknown, and it is also unclear whether the monarch?s ability to sequester cardenolides is a cause or a consequence of specializing on milkweed host plants. This research will answer these basic questions about monarchs while involving undergraduates from underrepresented groups in this investigation; educational workshops will encourage the citizen science practices.
The approaches below will link variation in genes (ATP?1 binding domain, transporters) to variation in a phenotype (sequestration ability) that affects the way that monarchs interact with their environment. In the first approach, the Fellow will leverage natural variation in cardenolide content of two milkweed species and natural variation in the ability of monarch populations to sequester cardenolides. Using experimental rearing and gene expression analysis, the Fellow will determine the genes involved in the process of cardenolide transport and storage, and how these genes differ in expression across hosts, monarch populations, and developmental stages. In the second approach, the Fellow will use ?evolution-in-reverse? to understand which evolved first: the monarch?s target site insensitivity to cardenolides or the ability to sequester cardenolides. The Fellow will use gene-editing techniques (CRISPR-Cas9) to introduce a series of stepwise mutations into the cardenolide target site (the Na+/K+-ATPase) to determine whether sequestration is still possible on a cardenolide-sensitive background. The Fellow will gain valuable training in molecular biology, chemical ecology, and bioinformatics as well as in outreach by expanding the Monarch Larvae Monitoring Program to Puerto Rico.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
