EAGER: RNA Polymerase V as a Novel Capacitor of Phenotypic Variation in Arabidopsis thalian

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Intellectual Merit. Biological systems are remarkably robust to genetic and environmental perturbations. Previous research identified the chaperone HSP90 as an important mechanism in maintaining phenotypic robustness. HSP90 perturbation decreases robustness and reveals cryptic genetic variation in plants, flies, fish, and yeast. Due to its property of concealing and releasing genetic variation, HSP90 has been named a capacitor of phenotypic variation. Another putative novel capacitor of phenotypic variation has now been identified in Arabidopsis thaliana: RNA polymerase V. Like HSP90, Pol V maintains phenotypic robustness. Whereas HSP90 functions primarily in protein folding, Pol V functions in RNA-directed DNA methylation, silencing transposons, tandem repeats, and intergenic regions, and drives compaction of rDNA. As a bona fide capacitor, functional Pol V should conceal genetic variation. In Aim 1, an innovative approach will be used to test whether functional Pol V conceals genetic variation. As Pol V affects chromatin states and genome stability, the increased phenotypic variation in pol V mutants may be caused by different, potentially heritable epigenetic or genetic states. If true, selection should fix these phenotypes. In Aim 2, selection experiments will be conducted by propagating individual seedlings with extremely long and short stems for wild-type and pol V mutants and then documenting a range of phenotypes to determine the selection response. In Aim 3, the extent of mechanistic overlap between HSP90 and Pol V, will be assessed by conducting a whole-genome expression analysis in plants with reduced levels of Pol V and HSP90. The proposed characterization of Pol V as a functionally distinct capacitor offers, for the first time, the opportunity to identify common molecular features that are associated with decreased robustness, either as causes or consequences. This project addresses the controversial, yet fundamental, concept of phenotypic capacitance by aiming to establish Pol V as a novel capacitor in A. thaliana. It breaks new ground by testing the hypothesis that functionally distinct capacitance mechanisms converge at common molecular features, in this case at chromatin.Broader Impacts. The project offers opportunities for student training at both graduate and undergraduate levels. Underrepresented minority students will participate in academic research, through an ongoing summer internship program developed and run by the PI. Collaborations with faculty at the University of New Mexico and Morehouse College will enable visits of University of Washington Genome Sciences faculty to both minority serving institutions and return visits to Seattle. These visits are aimed at expanding research horizons for both faculty and their graduate students, who will be tomorrow's faculty members.