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:Genome-wide analysis of gene expression has documented differential gene expression between closely related species in plants or animals and nonadditive gene expression in hybrids and allopolyploids compared to the parents. In Arabidopsis, 15-43% of genes are expressed differently between the related species, A. thaliana and A. arenosa, and the majority of them are nonadditvely expressed (differently from mid-parent value) in allotetraploids relative to the parents. The gene expression variation is associated with transcriptional and posttranscriptional mechanisms. Although transcriptional regulation by epigenetic mechanisms plays a role in nonadditive gene expression, the effects of posttranscriptional regulation on nonadditive gene expression is largely unknown. Here we reported a comprehensive genome-wide analysis of mRNA decay in Arabidopsis allotetraploids using oligo gene microarrays. Among ~26,000 annotated genes on the arrays, over 1% of genes showed a rapid decay rate with an estimated half-life of less than 60 min, and these genes are known as genes with unstable transcripts (GUTs). Interestingly, 30% of GUTs matched the nonadditively expressed genes, and their expression levels were significantly negatively correlated. These nonadditively expressed GUTs are highly enriched with a 2-8-fold increase compared to the proportion of all genes in the Gene Ontology (GO) classifications in response to stress, abiotic and biotic stimulus, signal transduction, and transcription. The data are consistent with the enrichment of nonadditvely-expressed genes in those categories in allopolyploids of Arabidopsis, wheat and cotton. Interestingly, the GUTs include some key transcription factors including circadian clock regulators, suggesting a mechanism for rapid response to light signalling and clock regulation in allotetraploids. These data collectively suggest an important role of mRNA stability in nonadditive expression of homoeologous genes in allopolyploids. A total of 8 slides were used for comparison (0 min vs. 120 min), including two biological and four technical replications. Each biological replication consists of two technical replications (four slides) that were hybridized with reverse-labeled probes.

Project description:Genome-wide analysis of gene expression has documented differential gene expression between closely related species in plants or animals and nonadditive gene expression in hybrids and allopolyploids compared to the parents. In Arabidopsis, 15-43% of genes are expressed differently between the related species, A. thaliana and A. arenosa, and the majority of them are nonadditvely expressed (differently from mid-parent value) in allotetraploids relative to the parents. The gene expression variation is associated with transcriptional and posttranscriptional mechanisms. Although transcriptional regulation by epigenetic mechanisms plays a role in nonadditive gene expression, the effects of posttranscriptional regulation on nonadditive gene expression is largely unknown. Here we reported a comprehensive genome-wide analysis of mRNA decay in Arabidopsis allotetraploids using oligo gene microarrays. Among ~26,000 annotated genes on the arrays, over 1% of genes showed a rapid decay rate with an estimated half-life of less than 60 min, and these genes are known as genes with unstable transcripts (GUTs). Interestingly, 30% of GUTs matched the nonadditively expressed genes, and their expression levels were significantly negatively correlated. These nonadditively expressed GUTs are highly enriched with a 2-8-fold increase compared to the proportion of all genes in the Gene Ontology (GO) classifications in response to stress, abiotic and biotic stimulus, signal transduction, and transcription. The data are consistent with the enrichment of nonadditvely-expressed genes in those categories in allopolyploids of Arabidopsis, wheat and cotton. Interestingly, the GUTs include some key transcription factors including circadian clock regulators, suggesting a mechanism for rapid response to light signalling and clock regulation in allotetraploids. These data collectively suggest an important role of mRNA stability in nonadditive expression of homoeologous genes in allopolyploids.

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Reduced DNA methylation in Arabidopsis allopolyploids induces genome-specific changes in gene expression

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