Poster abstracts

Poster number 43 submitted by Allison McClish

Cell-autonomous action of RNA polymerase IV maintains the epigenetic repression of a paramutant pl1 allele

Allison McClish (Department of Molecular Genetics, The Ohio State University), Brian Giacopelli (Molecular, Cellular and Developmental Biology Graduate Program, The Ohio State University), Jay B. Hollick (Department of Molecular Genetics, The Ohio State University; Center for RNA Biology, The Ohio State University)

Abstract:
Paramutation describes a heritable epigenetic change in gene regulation initiated by trans-homolog interactions and maintained by components, including the largest subunit of RNA polymerase IV (RPD1), required for the biogenesis of small RNA (sRNA)1,. Because sRNAs in eudicots can move from cell to cell, exerting non-cell-autonomous effects on gene expression, we tested the cell-autonomous action of presumed sRNAs in maintaining repressed expression of a paramutant purple plant1 (pl1) allele (Pl1-Rh) by evaluating genetic mosaics for anthocyanin production related to RPD1 function. RPD1 dysfunction is associated with increased pigmentation in plants that are homozygous for repressed Pl1-Rh alleles (designated Pl’ ). By comparing pigmentation in hemizygous rpd1 mutant sectors to that of adjacent non-mutant tissues we could evaluate the potential cell-autonomy of normal RPD1 function in repressing Pl’. If RPD1 function acts in a cell-autonomous manner, increased anthocyanin production would be expected throughout the sector, while non-cell-autonomous function would maintain pigment repression, at least at sector boundaries. One thousand nine plants (half heterozygous for the rpd1-9 mutant allele) from irradiated seeds were evaluated in summer 2016. Of the 72 sectors greater than 0.5cm in width that were examined, 60 had sharp boundaries of dark pigment coincident with the cell-autonomous albino phenotype marking RPD1 loss. This result indicates that RPD1 actions - including the resulting sRNAs - are cell autonomous in their ability to induce and maintain Pl’ states. This interpretation stands in contrast to results from grafting experiments in eudicots in which mobile sRNAs direct systemic epigenetic modifications3.

References:
1. Brink 1958 CSH Symp Quant Biol 23, 379
2. Erhard 2009 Science 27, 323
3. Lewsey 2016 PNAS 9, 113

Keywords: gene-regulation, mobility, maize