Project description:MicroRNAs (miRNAs) and small interfering RNAs (siRNAs) are produced in diverse species and control gene expression and epigenetic regulation. Although physiological and developmental roles of miRNAs and siRNAs have been extensively studied in plants and animals, expression diversity and evolution of miRNAs and siRNAs in closely related species are poorly understood. Here we report comprehensive analyses of miRNA expression and siRNA distribution in two closely related species (Arabidopsis thaliana and A. arenosa), a natural allotetraploid (A. suecica), and two resynthesized allotetraploid lines (F1 and F7) derived from A. thaliana and A. arenosa. The siRNA populations present in A. thaliana were maintained in resynthesized allotetraploids and A. suecica. Although miRNA sequences were highly conserved, their expression patterns were highly variable between the allotetraploids and their progenitors. Significantly, many miRNAs were nonadditively expressed in the allotetraploids relative to the parents and preferentially degraded A. thaliana or A. arenosa targets. Stable inheritance of parental siRNAs in allopolyploids helps maintain genome stability in response to M-bM-^@M-^\genomic shockM-bM-^@M-^], whereas expression diversity of miRNAs and their target preference lead to interspecies variation in gene expression, growth, and development. NOTE: sff files unavailable for Samples AaL and F1L. 10 samples examined: Arabidopsis thaliana leaf, flower, Arabidopsis arenosa leaf and flower, F1 synthetic allopolyploid leaf and flower, F7 synthetic allopolyploid leaf and flower, Arabidopsis suecica leaf and flower. To determine small RNA profiles in Arabidopsis allotetraploids and their progenitors, we made 10 small RNA libraries from rosette leaves (L) and flower buds (F) in five lines, A. thaliana, A. arenosa, Allo(F1), Allo733(F7), and A. suecica. To examine expression of small RNAs among related species and their hybrids, we employed miRNA microarrays and compared small RNA levels.
Project description:Hybridization to Affymetrix tiling array Ath 1.0R performed using gDNA from Arabidopsis arenosa var. Care-1, Arabidopsis thaliana var 4x Ler, Arabidopsis suecica var. Sue-1, and F1 hybrids between A. thaliana var 4x Ler and A. arenosa var. Care-1
Project description: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 suecica is a natural allotetraploid derived from the extant species A. thaliana and A. arenosa. Here we report that reduced DNA methylation in met1-RNAi A. suecica lines altered the expression of ~200 genes encoding transposons, centromeric and heterochromatic RNAs, and predicted proteins. Reduced DNA methylation occurred frequently in promoter regions of the upregulated genes but not of the repressed genes and led to increased mobility of En/Spm-like transposons in met1-RNAi A. suecica lines. Compared to A. arenosa centromeres, A. thaliana centromeres were hypermethylated, which correlates with higher levels of small RNA accumulation in A. thaliana centromeres than that in A. arenosa centromeres. Derepression of the genes examined was primarily derived from A. thaliana subgenome, and A. arenosa genes are less affected by methylation defects. Moreover, non-CG (CC) methylation in the promoter region of A. thaliana At2g23810 was maintained in resynthesized allotetraploids, and the methylation spread within the promoter region in natural A. suecica, leading to silencing of At2g23810, which was demethylated and reactivated in met1-RNAi A. suecica lines. We suggest that a subset of A. thaliana and A. arenosa genes are differentially methylated in natural allopolyploids, and some A. thaliana genes including centromeres are subjected to transcriptional repression and genome-specific RNA-mediated DNA methylation in Arabidopsis allopolyploids. Keywords: gene expression in reduced DNA methylation lines in Arabidopsis allotetraploids
