Poster abstracts

Poster number 37 submitted by Natalie Deans

Proper ontogeny and maintenance of paramutant states in Zea mays is defined by required to maintain repression3 function

Natalie C. Deans (Department of Molecular Genetics, The Ohio State University, Columbus, OH), Janelle M. Gabriel, Elizabeth J. Bashian, Amiel Emerson (Department of Molecular Genetics, The Ohio State University, Columbus, OH), Stacey A. Simon (Delaware Biotechnology Institute, University of Delaware, Newark, DE), Charles Addo-Quaye, Brian P. Dilkes (Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN ), Blake C. Meyers (Division of Plant Sciences, University of Missouri, Columbia, MO, The Donald Danforth Plant Science Center, St. Louis, MO), Jay B. Hollick (Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, OH)

Abstract:
Specific purple plant1 alleles undergo paramutation1, a behavior resulting in heritable epigenetic changes in gene regulation. Only repressed paramutant states (Pl´ ) are transmitted from Pl´ / Pl-Rh heterozygotes in apparent violation of Mendel’s law of segregation. Ethylmethane sulfonate-induced mutations isolated in a screen for loss of Pl´ repression identify at least fifteen required to maintain repression (rmr) loci. All six RMR-type proteins identified to date are involved in DNA-dependent RNA polymerase IV (Pol IV)-mediated 24 nucleotide (24nt) RNA biogenesis and are presumably orthologous to components of an Arabidopsis RNA-directed DNA Methylation (RdDM) pathway involved in silencing transposons. Although the biological roles of these 24nt RNAs in maize remain unclear, loss of the shared Pol IVa and Pol IVb largest subunit leads to global changes in Pol II transcription and gene dysregulations2,3 associated with specific developmental defects4. Here we characterize a recessive mutation (rmr3-1) defining the rmr3 locus that is distinguished from all known rmr mutations by specifying a unique phenotype of short stature, delayed flowering, and progressive leaf necrosis. This rmr3 defect also correlates with reduced levels of 24nt RNAs representing repetitious features in developing cobs. Molecular mapping aided by whole-genome sequence places rmr3 in a 12Mbp interval on chromosome 2 containing 186 gene models, though none encode potentially orthologous RdDM proteins. Possible candidates affecting chromatin condensation or RNA polymerase assembly are considered. Cloning rmr3 will identify a novel component of 24nt RNA biogenesis having a role in developmental gene control distinct from that of Pol IV.

References:
1. Hollick et al. 1995 Genetics 141, 709. | 2. Erhard et al. 2015 Genetics 199, 1107. | 3. Hale et al. 2009 PLoS Genetics 5, e1000598. | 4. Parkinson et al. 2007 Developmental Biology 308, 462.

Keywords: Epigenetics, small RNAs, Transcription