NSF PRFB FY 2023: Investigating enhancer and protein divergence at follistatin paralogs underlying genetic assimilation of wing plasticity

Deem, Kevin D, Rochester NY

Investigators

Abstract

This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2023, 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. Today's diversity of plant and animal forms observable in nature arises from accumulated morphological innovations. Despite the scientific interest in this topic, the evolutionary processes that give rise to new forms are still surrounded by mystery and debate. One promising model is genetic assimilation, in which new forms that have emerged from environmentally induced variation (phenotypic plasticity), can later become genetically determined. However, it remains unclear how such a switch from environmental to genetic control might occur. This project aims to characterize the molecular mechanisms facilitating genetic assimilation, to further our understanding of morphological novelty, diversity, and evolution. As a study system, the fellow will utilize the pea aphid, in which a female form variation has been genetically assimilated in males by changes in their DNA. Pea aphids produce two types of wingless morphs: asexual wingless females induced by maternal environment (wing polyphenism, a type of phenotypic plasticity), and genetically determined wingless males (genetic assimilation). Importantly, the shorthand term "wingless" used here describes not only a loss of wings, but a systemic change in metabolic, behavioral, and multiple morphological character states. Thus, "wingless" pea aphid morphs comprise a bona fide example of phenotypic novelty. Two duplicates of the gene follistatin (fs), a TGF-beta ligand inhibitor, are separately involved in male and female wingless morph determination. The duplicate fs2 is upregulated in wingless females, while the presence of the fs3 duplicate determines wingless male morphs. Both duplicates exhibit changes to their protein coding and putative regulatory regions. The fellow will use cutting edge experimental techniques to characterize changes in cis-regulation (Aim 1), signatures of selection (Aim 2), and protein function (Aim 3) at fs paralogs, to determine how duplication and divergence facilitated genetic assimilation. 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.