TITLE

RNAi of met1 Reduces DNA Methylation and Induces Genome-Specific Changes in Gene Expression and Centromeric Small RNA Accumulation in Arabidopsis Allopolyploids

AUTHOR(S)
Meng Chen; Ha, Misook; Lackey, Erika; Jianlin Wang; Chen, Z. Jeffrey
PUB. DATE
April 2008
SOURCE
Genetics;Apr2008, Vol. 178 Issue 4, p1845
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Changes in genome structure and gene expression have been documented in both resynthesized and natural allopolyploids that contain two or more divergent genomes. The underlying mechanisms for rapid and stochastic changes in gene expression are unknown. Arabidopsis suecicais a natural allotetraploid derived from the extant A. thaliana and A. arenosa genomes that are homeologous in the allotetraploid. Here we report that RNAi of meti reduced DNA methylation and altered the expression of ~2OO genes, many of which encode transposons, predicted proteins, and centromeric and heterochromatic RNAs. Reduced DNA methylation occurred frequently in promoter regions of the upregulated genes, and an En/Spm-like transposon was reactivated in metl-RNAi A. suecica lines. Derepression of transposons, heterochromatic repeats, and ccii- tromeric small RNAs was primarily derived from the A. thaliana genome, and A. arenosa homeologous loci were less affected by methylation defects. A high level of A. thaliana centromeric small RNA accumulation was correlated with hypermethylation of A. thaliana centromeres. The greater effects of reduced DNA methylation on transposons and centromeric repeats in A. thaliana than in A. arenosa are consistent with the repression of many genes that are expressed at higher levels in A. thaliana than in A. arenosa in the resynthesized allotetraploids. Moreover, non-CG (CC) methylation in the promoter region of A. thaliana At2g23810 remained in the resynthesized allotetraploids, and the methylation spread within the promoter region in natural A. suecica, leading to silencing ofAt2g238l 0. At2g238 10 was demethylated and reactivated in met 1-RNAi A. suecica lines. We suggest that many A. thaliana genes are tran~scriptionally repressed in resynthesized allotetraploids, and a subset of A. thaliana loci including transposons and centromeric repeats are heavily methylated and subjected to homeologous genome-specific RNA-mediated DNA methylation in natural allopolyploids.
ACCESSION #
31866759

 

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