RUI: The molecular basis of a genetically accommodated larval color polyphenism

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Phenotypic plasticity refers to the ability of an organism to generate distinct morphological, behavioral or metabolic changes in response to environmental changes. Laboratory and theoretical research has shown that phenotypic plasticity may play an important role in shaping the evolutionary trajectory of species, although the underlying mechanism remains poorly understood. This project will lead to a better understanding of the molecular and physiological basis of phenotypic plasticity by comparing two strains of caterpillars that differ in their response to temperature: one strain remains black at all temperatures and another turns green at higher temperatures. Black caterpillars have lower levels of juvenile hormone than green caterpillars, and the project will elucidate the regulation of this important hormone that controls insect growth and development. Determining the molecular and physiological basis of phenotypic plasticity has important implications for our understanding of environmentally-induced diseases, generation of novel traits, and species conservation. Much of the proposed study will involve female undergraduate researchers from Wellesley College who will be exposed to research in integrative biology. These students will be encouraged to present at national meetings and publish their contribution in peer-reviewed journals. The award will support inquiry-based learning in the classroom, and will also expose undergraduate and high school students from underrepresented groups to scientific research.The specific goal of the proposed study is to determine the genetic mechanism underlying the evolution of an artificially selected polyphenism. In this study, the transcriptomes of the neuroendocrine complex in a monophenic strain of the tobacco hornworm, Manduca sexta, and the polyphenic strain will be compared, as these strains differ in the temperature sensitivity of juvenile hormone production. Once candidate temperature-sensitive genes are identified, the flour beetle Tribolium castaneum and RNA interference techniques will be used to functionally characterize these genes. The project will uncover the genetic basis of genetic accommodation and identify the molecular nature of hidden genetic variation, which remains poorly understood. It will lead to a mechanistic understanding of genotype-phenotype-environment interactions and advance understanding of molecular and physiological control of juvenile hormone production. Determining the molecular nature of genetic accommodation and phenotypic plasticity has implications for our understanding of evolution. The findings may also help identify novel regulators of juvenile hormone that could serve as potential targets for pest management. By involving high school and college students in the research and integrating teaching with research, the project also contributes to training the next generation of scientists.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.