title: A Role for CHH Methylation in the Parent-of-Origin Effect on Altered Circadian Rhythms and Biomass Heterosis in Arabidopsis Intraspecific Hybrids.
abstract: Hybrid plants and animals often show increased levels of growth and fitness, a phenomenon known as hybrid vigor or heterosis. Circadian rhythms optimize physiology and metabolism in plants and animals. In plant hybrids and polyploids, expression changes of the genes within the circadian regulatory network, such as CIRCADIAN CLOCK ASSOCIATED1 (CCA1), lead to heterosis. However, the relationship between allelic CCA1 expression and heterosis has remained elusive. Here, we show a parent-of-origin effect on altered circadian rhythms and heterosis in Arabidopsis thaliana F1 hybrids. This parent-of-origin effect on biomass heterosis correlates with altered CCA1 expression amplitudes, which are associated with methylation levels of CHH (where H = A, T, or C) sites in the promoter region. The direction of rhythmic expression and hybrid vigor is reversed in reciprocal F1 crosses involving mutants that are defective in the RNA-directed DNA methylation pathway (argonaute4 and nuclear RNA polymerase D1a) but not in the maintenance methylation pathway (methyltransferase1 and decrease in DNA methylation1). This parent-of-origin effect on circadian regulation and heterosis is established during early embryogenesis and maintained throughout growth and development.
authors.affiliation: Department of Molecular Biosciences, Center for Computational Biology and Bioinformatics and Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712-0159 Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong.
authors.forename: Danny W-K
authors.initials: DW
authors.lastname: Ng
authors.affiliation: Department of Molecular Biosciences, Center for Computational Biology and Bioinformatics and Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712-0159.
authors.forename: Marisa
authors.initials: M
authors.lastname: Miller
authors.affiliation: Department of Molecular Biosciences, Center for Computational Biology and Bioinformatics and Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712-0159.
authors.forename: Helen H
authors.initials: HH
authors.lastname: Yu
authors.affiliation: Department of Molecular Biosciences, Center for Computational Biology and Bioinformatics and Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712-0159.
authors.forename: Tien-Yu
authors.initials: TY
authors.lastname: Huang
authors.affiliation: Department of Molecular Biosciences, Center for Computational Biology and Bioinformatics and Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712-0159.
authors.forename: Eun-Deok
authors.initials: ED
authors.lastname: Kim
authors.affiliation: Department of Molecular Biosciences, Center for Computational Biology and Bioinformatics and Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712-0159.
authors.forename: Jie
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755-3563.
authors.forename: Qiguang
authors.initials: Q
authors.lastname: Xie
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755-3563.
authors.forename: C Robertson
authors.initials: CR
authors.lastname: McClung
authors.affiliation: Department of Molecular Biosciences, Center for Computational Biology and Bioinformatics and Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712-0159 State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, China zjchen@austin.utexas.edu.
authors.forename: Z Jeffrey
authors.initials: ZJ
authors.lastname: Chen