title: Function of the DEMETER DNA glycosylase in the Arabidopsis thaliana male gametophyte.
abstract: In double fertilization, the vegetative cell of the male gametophyte (pollen) germinates and forms a pollen tube that brings to the female gametophyte two sperm cells that fertilize the egg and central cell to form the embryo and endosperm, respectively. The 5-methylcytosine DNA glycosylase DEMETER (DME), expressed in the central cell, is required for maternal allele demethylation and gene imprinting in the endosperm. By contrast, little is known about the function of DME in the male gametophyte. Here we show that reduced transmission of the paternal mutant dme allele in certain ecotypes reflects, at least in part, defective pollen germination. DME RNA is detected in pollen, but not in isolated sperm cells, suggesting that DME is expressed in the vegetative cell. Bisulfite sequencing experiments show that imprinted genes (MEA and FWA) and a repetitive element (Mu1a) are hypomethylated in the vegetative cell genome compared with the sperm genome, which is a process that requires DME. Moreover, we show that MEA and FWA RNA are detectable in pollen, but not in isolated sperm cells, suggesting that their expression occurs primarily in the vegetative cell. These results suggest that DME is active and demethylates similar genes and transposons in the genomes of the vegetative and central cells in the male and female gametophytes, respectively. Although the genome of the vegetative cell does not participate in double fertilization, its DME-mediated demethylation is important for male fertility and may contribute to the reconfiguration of the methylation landscape that occurs in the vegetative cell genome.
authors.affiliation: Gregor Mendel Institute, Austrian Academy of Sciences, 1030 Vienna, Austria.
authors.forename: Vera K
authors.initials: VK
authors.lastname: Schoft
authors.forename: Nina
authors.initials: N
authors.lastname: Chumak
authors.forename: Yeonhee
authors.initials: Y
authors.lastname: Choi
authors.forename: Mike
authors.initials: M
authors.lastname: Hannon
authors.forename: Marcelina
authors.initials: M
authors.lastname: Garcia-Aguilar
authors.forename: Adriana
authors.initials: A
authors.lastname: Machlicova
authors.forename: Lucyna
authors.initials: L
authors.lastname: Slusarz
authors.forename: Magdalena
authors.initials: M
authors.lastname: Mosiolek
authors.forename: Jin-Sup
authors.initials: JS
authors.lastname: Park
authors.forename: Guen Tae
authors.initials: GT
authors.lastname: Park
authors.forename: Robert L
authors.initials: RL
authors.lastname: Fischer
authors.forename: Hisashi
authors.initials: H
authors.lastname: Tamaru
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D019175:DNA Methylation; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018392:Genomic Imprinting; D018525:Germination / Q000235:genetics / Q000502:physiology; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000235:genetics / Q000378:metabolism*; D056771:Ovule / Q000235:genetics / Q000378:metabolism; D011058:Pollen / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D015534:Trans-Activators; C463261:DEMETER protein, Arabidopsis; D009699:N-Glycosyl Hydrolases