DEMETER, a DNA Glycosylase Domain Protein, Is Required for Endosperm Gene Imprinting and Seed Viability in Arabidopsis (original) (raw)

et al., 1999). Thus, double fertilization generates a seed with a triploid endosperm and diploid embryo. The embryo generates organs (axis and cotyledon), tissues (protoderm, procambium, and ground meristem), and meristems (shoot and root). The fertilized central cell mediates the transfer of nutrients from maternal tissues to be absorbed by the embryo (Brown et al., 1999). Biology University of California, Los Angeles To gain insights into the maternal control of embryo and endosperm development, mutations in a small num-Los Angeles, California 90095 3 Section of Plant Biology ber of genes have been identified where seed viability depends upon the genotype of the maternal allele. For Division of Biological Sciences University of California, Davis example, these studies have shown that the female gametophyte provides the embryo with an MCM-related Davis, California 95616 4 Molecular Biology Institute protein, PROLIFERA (PRL), necessary for cytokinesis (Springer and Holding, 2002). Also, wild-type maternal University of California, Los Angeles Los Angeles, California 90095 alleles encoding Polycomb group proteins are necessary for proper female gametophyte and seed development. MEDEA (MEA), FERTILIZATION INDEPENDENT ENDOSPERM (FIE), and FERTILIZATION INDEPEN-Summary DENT SEED2 (FIS2) encode SET-domain, WD domain, and zinc finger Polycomb group proteins (Grossniklaus We isolated mutations in Arabidopsis to understand et al., 1998; Kiyosue et al., 1999; Luo et al., 1999; Ohad how the female gametophyte controls embryo and enet al., 1999; Birve et al., 2001). Polycomb group proteins dosperm development. For the DEMETER (DME) gene, repress gene transcription by forming complexes that seed viability depends only on the maternal allele. DME remodel chromatin structure at specific regions within encodes a large protein with DNA glycosylase and nuclear localization domains. DME is expressed pri-the genome (Francis and Kingston, 2001). One function marily in the central cell of the female gametophyte, of MEA, FIE, and FIS2 is to prevent the onset of central the progenitor of the endosperm. DME is required for cell proliferation and endosperm development prior to maternal allele expression of the imprinted MEDEA fertilization and to repress endosperm growth and devel-(MEA) Polycomb gene in the central cell and endoopment after fertilization (Kiyosue et al., 1999; Vinkesperm. Ectopic DME expression in endosperm actinoog et al., 2000). Thus, to date, no genes have been vates expression of the normally silenced paternal discovered that function primarily prior to fertilization in MEA allele. In leaf, ectopic DME expression induces the female gametophyte to control processes essential MEA and nicks the MEA promoter. Thus, a DNA glycofor subsequent embryo and endosperm development sylase activates maternal expression of an imprinted after fertilization. gene in the central cell. Because only the maternal allele is required for seed viability, loss-of-function mea, fie, fis2, and prl mutations Jiricny, J. (2002). An APE that proofreads. Nature 415, 593-594. Mutations in the FIE and MEA genes that encode interacting poly-M., and Jost, Y.-C. (2001). 5-methylcytosine DNA glycosylase particcomb proteins cause parent-of-origin effects on seed development ipates in the genome-wide loss of DNA methylation occurring during by distinct mechanisms. Plant Cell 12, 2367-2381. mouse myoblast differentiation. Nucleic Acids Res 29, 4452-4461. Kakutani, T., Jeddeloh, J.A., Flowers, S.K., Munakata, K., and Rich-Accession Numbers ards, E.J. (1996). Developmental abnormalities and epimutations associated with DNA hypomethylation mutations. Proc. Natl. Acad. The DME cDNA sequence has been deposited in GenBank as acces-Sci. USA 93, 12406-12411. sion number AF521596. Kasinsky, H.E., Lewis, J.D., Dacks, J.B., and Ausio, J. (2001). Origin of H1 linker histones. FASEB J. 15, 34-42.