Control of FWA gene silencing in Arabidopsis thaliana by SINE-related direct repeats

• Published in: The Plant journal : for cell and molecular biology Vol. 49; no. 1; pp. 38 - 45
• Main Authors: Kinoshita, Yuki, Saze, Hidetoshi, Kinoshita, Tetsu, Miura, Asuka, Soppe, Wim J.J, Koornneef, Maarten, Kakutani, Tetsuji
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-01-2007; Blackwell Publishing Ltd; Blackwell Science
• Subjects: Agronomy. Soil science and plant productions; Arabidopsis - genetics; Arabidopsis Proteins - genetics; Arabidopsis thaliana; Biological and medical sciences; Botany; Classical and quantitative genetics. Population genetics. Molecular genetics; cytosine methylation; DNA methylation; epigenetic; epigenetic control; epigenetics; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Plant - genetics; Gene Silencing; Generalities. Genetics. Plant material; Genetics and breeding of economic plants; Homeodomain Proteins - genetics; imprinting; locus; maintenance; medea polycomb gene; Molecular and cellular biology; Molecular biology; Molecular genetics; mutants; novo dna methylation; Plants, Genetically Modified; Repetitive Sequences, Nucleic Acid - genetics; RNA-directed DNA methylation; Short Interspersed Nucleotide Elements - genetics; small rnas; tandem repeats; Transcription Factors - genetics; transposon; transposons; Double stranded RNA; Transcription; imprinting; epigenetic; RNA-directed DNA methylation; Arabidopsis thaliana; transposon; Gene silencing; Gene; Cruciferae; Dicotyledones; Angiospermae; Development; DNA methylation; Flowering; Spermatophyta; Mutation
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313x.2006.02936.x

A unique feature of late-flowering fwa epigenetic mutations is that the phenotype is caused by ectopic expression of the homeobox gene FWA. During normal development the FWA gene is expressed specifically in the endosperm in an imprinted manner. Ectopic FWA expression and disruption of imprinting can be induced in mutants of a CG methyltransferase MET1 (methyltransferase 1) or a chromatin-remodeling gene DDM1 (decrease in DNA methylation 1), suggesting that the proper FWA expression depends on cytosine methylation. However, critical methylated residues controlling FWA silencing are not pinpointed. Nor is it understood how the FWA gene is initially methylated and silenced in wild-type plants. Here we mapped sequences critical for FWA silencing by application of RdDM (RNA-directed DNA methylation) to a ddm1-induced stable fwa epiallele. Transcription of double-stranded RNA corresponding to the tandem direct repeats around the FWA transcription start site induced de novo DNA methylation, transcriptional suppression and phenotypic reversion. The induced changes were heritable even without the transgene, which correlates with inheritance of CG methylation in the direct repeats. The newly silenced FWA allele was transcribed in an endosperm-specific and imprinted manner, as is the case for the wild-type FWA gene. The results indicate that methylation of the direct repeats, which presumably originated from a short interspersed nuclear element (SINE), is sufficient to induce proper epigenetic control of the FWA gene.