Poster abstracts
Poster number 6 submitted by Natalie Deans
Pl1-Rhoades paramutation is associated with molecular changes at downstream tandem repeats
Natalie C. Deans (Department of Molecular Genetics and Centers for Applied Plant Sciences and RNA Biology, The Ohio State University, Columbus, OH, 43210), Joy-El R.B. Talbot (Department of Molecular Genetics, The Ohio State University, Columbus, OH, 43210; Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200), Cristian Sez-Gonzlez, Mowei Li (Department of Molecular Genetics and Centers for Applied Plant Sciences and RNA Biology, The Ohio State University, Columbus, OH, 43210), Chris Watkins, Darren Heavens (The Earlham Institute, Norwich Research Park, Norwich, NR4 7UH, UK), Mario Caccamo (The Earlham Institute, Norwich Research Park, Norwich, NR4 7UH, UK; NIAB, Cambridge, CB3 0LE, UK), Jay B. Hollick (Department of Molecular Genetics and Centers for Applied Plant Sciences and RNA Biology, The Ohio State University; Department of Molecular and Cell Biology, University of California, Berkeley)
Abstract:
In maize, paramutations result in meiotically-heritable regulatory changes of certain alleles including Pl1-Rhoades which encodes a transcription factor required for anthocyanin production[1,2]. A strongly-expressed Pl1-Rhoades allele (denoted Pl-Rh ) is suppressed in trans when combined with a transcriptionally and post-transcriptionally repressed Pl1-Rhoades allele (denoted Pl´ ), and both alleles are subsequently sexually transmitted in a Pl´-like state. Mutant screens have identified at least sixteen loci whose functions are required to maintain repression (rmr) of Pl´ [ 3,4]. Known RMR proteins include subunits of a plant specific DNA-dependent RNA polymerase (Pol IV)[5,6] and others that influence 24nt RNAs[4,7,8] which, in Arabidopsis, facilitate repressive chromatin modifications. Although structural analyses of other maize alleles subject to paramutation identify distinct repeats as a common feature[9,10,11], the mechanisms and specific sequences that facilitate paramutation remain largely unknown. Here we report that a region downstream of the Pl1-Rhoades coding sequence conferring strong expression and paramutation behavior[12] contains five ~2kb direct repeats while the weakly paramutagenic CML52 and nonparamutagenic B73 haplotypes have three and one, respectively. Repeat RNA levels correlate with Pl1-Rhoades expression. Pol IV-dependent 24nt RNAs at these repeats indicate RMR proteins operate at this feature. Additional fractionation-based experiments revealed alternate nucleosome profiles within these repeats distinguishing allele states. How these repeats to facilitate paramutations remains an open question. We are currently identifying additional molecular features distinguishing alternate Pl1-Rhoades states and characterizing these regulatory transitions to determine how maize generates, maintains, and transmits meiotically-heritable regulatory variation.
References:
1 Hollick et al. 1995 Genetics 141, 709 | 2 Cone et al. 1993 Plant Cell 5, 1795 | 3 Hollick and Chandler 2001 Genetics 157, 369 | 4 Hale et al. 2007 PLoS Biol. 5, 2156 | 5 Erhard et al. 2009 Science 323, 1201 | 6 Stonaker et al. 2009 PLoS Genet. 5, e1000706 | 7 Nobuta et al. 2008 PNAS 105, 14958 | 8 Barbour et al. 2012 Plant Cell 24, 1761 | 9 Stam et al. 2002 Genes and Dev. 16, 1906 | 10 Kermicle et al. 1995 Genetics 141, 361 | 11 Goettel and Messing 2013 Theor. Appl. Genet. 126, 159 | 12 Erhard et al. 2013 Plant Cell 25, 808
Keywords: Enhancer, Gene regulation, Paramutation