The reduced expression of endogenous duplications (REED) in the maize R gene family is mediated by DNA methylation.

Ronchi, Angela; Petroni, Katia; Tonelli, Chiara

doi:10.1002/j.1460-2075.1995.tb00216.x

Cited by 59 publications

(38 citation statements)

References 66 publications

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“…For example, duplication of chalcone synthase genes in soybean results in a trans-dominant suppression of homologous genes (Todd and Vodkin, 1996). Duplications of phosphoribosylanthranilate isomerase (PAI) genes in Arabidopsis (Bender and Fink, 1995) and the R gene family in maize (Ronchi et al, 1995) induce DNA methylation of homologous genes and cause gene silencing. Lgc1 is not a mutation that involves duplication, but it has a structure similar to that of some mutations that do involve duplication.…”

Section: Lgc1 Is a Possible Hairpin Rna-producing Structurementioning

confidence: 99%

Low glutelin content1: A Dominant Mutation That Suppresses the Glutelin Multigene Family via RNA Silencing in Rice[W]

et al. 2003

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Low glutelin content1 ( Lgc1 ) is a dominant mutation that reduces glutelin content in rice grains. Glutelin is a major seed storage protein encoded by a multigene family. RNA gel blot and reverse transcriptase-mediated PCR analyses revealed that Lgc1 acts at the mRNA level in a similarity-dependent manner. In Lgc1 homozygotes, there is a 3.5-kb deletion between two highly similar glutelin genes that forms a tail-to-tail inverted repeat, which might produce a double-stranded RNA molecule, a potent inducer of RNA silencing. The hypothesis that Lgc1 suppresses glutelin expression via RNA silencing is supported by transgenic analysis using this Lgc1 candidate region, by reporter gene analysis, and by the detection of small interfering RNAs. In this context, Lgc1 provides an interesting example of RNA silencing occurring among genes that exhibit various levels of similarity to an RNA-silencing-inducing gene. Possible mechanisms for gene silencing of the glutelin multigene family by Lgc1 are discussed.

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Section: Lgc1 Is a Possible Hairpin Rna-producing Structurementioning

confidence: 99%

Low glutelin content1: A Dominant Mutation That Suppresses the Glutelin Multigene Family via RNA Silencing in Rice[W]

et al. 2003

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“…There is an inverse correlation of the near colorless phenotype produced by these alleles with the copy number of the duplicated rgenes, suggesting a copy number-silencing mechanism. The R locus is able to silence expression of certain alleles of the nonallelic, duplicated Sn locus that is 90% similar in sequence to the R gene (Ronchi et al, 1995). There are no structural changes in the Sn alleles, but an increase in methylation of the Sn promoter is correlated with suppression of the nonallelic Sn gene.…”

Section: Gene-silencing Phenomenamentioning

confidence: 99%

Duplications That Suppress and Deletions That Restore Expression from a Chalcone Synthase Multigene Family.

1996

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Seed coat color in soybean is determined by four alleles of the classically defined I (inhibitor) locus that controls the presence or absence as well as the spatial distribution of anthocyanin pigments in the seed coat. By analyzing spontaneous mutations of the I locus, we demonstrated that the I locus is a region of chalcone synthase (CHS) gene dupllcations. Paradoxically, deletions of CHS gene sequences allow higher levels of CHS mRNAs and restore pigmentation to the seed coat. The unusual nature of the I locus suggests that its dominant alleles may represent naturally occurring examples of homology-dependent gene silenclng and that the spontaneous deletions erase the gene-silencing phenomena. Specifically, mutations from the dominant i' allele (yellow seed coats wlth pigmented hila) to the recessive i allele (fully pigmented) can be associated wlth the absence of a 2.3-W Hindlll fragment that carries CHS4, a member of the multigene CHS family. Seven independent mutatlons exhibit deletions in the CHS4 promoter mgion. The dominant I allele (yellow seed coats) exhibits an extra 12.1-kb Hindlll fragment that hybridlzes with both the CHS coding region and CHSí promoter-specific probes. Mutatlons of the dominant I allele to the mcessive i allele (pigmented seed coats) give rise to 10.4-or 9.6-kb Hindlll CHS fragments that have lost the duplicated CHSí promoter. Finally, gene expression analysis demonstrated that heterozygous plants (//i) wlth yellow seed coats have reduced mRNA levels, indlcatlng that the 12.1-kb Hindlll CHS fragment associated with the dominant I allele inhibits pigmentation in a trans-dominant manner. Moreover, CHS gene-specific expression in seed coats shows that multiple CHS genes are expressed ln seed coats.

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“…Tandemly repeated transgenes are often silenced. This repeat-induced gene silencing (RIGS) has also been observed in untransformed plants for tandemly linked homologous host genes (18,51,66). RIGS is frequently associated with an increased level of DNA methylation (1,26,31,36,73).…”

mentioning

confidence: 94%

Position-Dependent Methylation and Transcriptional Silencing of Transgenes in Inverted T-DNA Repeats: Implications for Posttranscriptional Silencing of Homologous Host Genes in Plants

Stam

Viterbo

Mol

et al. 1998

Molecular and Cellular Biology

131

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Posttranscriptional silencing of chalcone synthase (Chs) genes in petunia transformants occurs by introducing T-DNAs that contain a promoter-driven or promoterless Chs transgene. With the constructs we used, silencing occurs only by T-DNA loci which are composed of two or more T-DNA copies that are arranged as inverted repeats (IRs). Since we are interested in the mechanism by which these IR loci induce silencing, we have analyzed different IR loci and nonsilencing single-copy (S) T-DNA loci with respect to the expression and methylation of the transgenes residing in these loci. We show that in an IR locus, the transgenes located proximal to the IR center are much more highly methylated than are the distal genes. A strong silencing locus composed of three inverted T-DNAs bearing promoterless Chs transgenes was methylated across the entire locus. The host Chs genes in untransformed plants were moderately methylated, and no change in methylation was detected when the genes were silenced. Run-on transcription assays showed that promoter-driven transgenes located proximal to the center of a particular IR are transcriptionally more repressed than are the distal genes of the same IR locus. Transcription of the promoterless Chs transgenes could not be detected. In the primary transformant, some of the IR loci were detected together with an unlinked S locus. We observed that the methylation and expression characteristics of the transgenes of these S loci were comparable to those of the partner IR loci, suggesting that there has been cross talk between the two types of loci. Despite the similar features, S loci are unable to induce silencing, indicating that the palindromic arrangement of the Chs transgenes in the IR loci is critical for silencing. Since transcriptionally silenced transgenes in IRs can trigger posttranscriptional silencing of the host genes, our data are most consistent with a model of silencing in which the transgenes physically interact with the homologous host gene(s). The interaction may alter epigenetic features other than methylation, thereby impairing the regular production of mRNA.Genes that are packaged into heterochromatin or whose promoters are heavily methylated are often transcriptionally repressed. These epigenetic gene inactivation mechanisms are known to be involved in genomic imprinting (2) and X-chromosome inactivation in mammals (78), in the control of homeotic genes in flies (29), and in the repression of silent mating-type loci in yeast (33). Also, the expression of transgenes in genetically modified animals (13-15), plants (4,12,37,42,64), and lower eukaryotes (52) is often epigenetically controlled. Transgenes usually integrate into the genome at random positions, and their expression is therefore affected by chromosomal position effects. Besides the chromosomal position, the number of transgene copies integrated at a particular chromosomal site affects their expression (15,42,64). Tandemly repeated transgenes are often silenced. This repeat-induced gene silencing (RIGS) has also b...

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The reduced expression of endogenous duplications (REED) in the maize R gene family is mediated by DNA methylation.

Cited by 59 publications

References 66 publications

Low glutelin content1: A Dominant Mutation That Suppresses the Glutelin Multigene Family via RNA Silencing in Rice[W]

Low glutelin content1: A Dominant Mutation That Suppresses the Glutelin Multigene Family via RNA Silencing in Rice[W]

Duplications That Suppress and Deletions That Restore Expression from a Chalcone Synthase Multigene Family.

Position-Dependent Methylation and Transcriptional Silencing of Transgenes in Inverted T-DNA Repeats: Implications for Posttranscriptional Silencing of Homologous Host Genes in Plants

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