Steroid-mediated Chromatin Remodeling in Developmental Plasticity

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Developmental plasticity is the ability of an organism to alter its development in response to external cues. This is significant because it allows plants and animals to adapt to changing environmental conditions. Developmental plasticity is an important and widespread phenomenon, however there is only limited understanding of the mechanistic basis of how external information is translated into changes in organismal development. In some cases, it is well understood how animals respond to environmental cues through production of hormones, and how these hormone signals are translated into developmental changes. What is less known, however, is how these environmentally induced hormone signals are translated into developmental changes in specific tissues. With this work, the investigators will use buckeye butterflies as a model to examine how environmental cues can coordinate tissue-specific changes in gene expression through the large-scale alteration of DNA structure. The buckeye butterfly serves as a powerful model system for studying plasticity because different populations show variation in their responses to seasonal cues, thus allowing isolation of genetic elements that control and tune plasticity in natural populations. Findings from this work will help in developing a new understanding of how environmental cues can induce developmental changes through large-scale modification of DNA structure. Such knowledge forms the basis for predicting organismal response to changing environments. Training of undergraduate and graduate students in modern biological investigations of genetic and developmental science is integral to the project. This includes the recruitment of members of under-represented groups in science. Developmentally, phenotypic plasticity can be characterized as a three-part process. First, a cue such as nutrition, temperature, photoperiod, crowding, or predator presence, is sensed by the organism and then translated into an internal signal, which is often endocrine in nature. Second, cells throughout the organism receive the signal in a manner that often appears to be tissue-specific. Third, molecular machinery within cells processes and responds to the signal, resulting in changes in gene regulation, thus altering development. While the physiological basis of phenotypic plasticity has been well described in many systems, it is only in recent years that studies have started to look at the molecular and genetic mechanisms of how development responds to plasticity-inducing physiological signals. This question is particularly compelling because different tissues respond differently to signals, and the mode and degree of response of different tissues can change quickly between generations. However, it is still unclear how tissue-specific plastic phenotypes can be rapidly modulated by environmentally induced endocrine signals. With this work Reed and colleagues will study how endocrine signaling and chromatin organization interact to induce seasonal developmental plasticity in the buckeye butterfly Junonia coenia. A well-characterized endocrine signal, natural genetic variation in seasonal reaction norms, and the ability to apply experimental approaches including ATAC-seq and CRISPR genome editing makes this species an ideal model to address how endocrine signaling mediates genome-wide chromatin remodeling, and how chromatin remodeling induces tissue-specific plastic phenotypes.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.