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.

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:One of the major players controlling RNA decay is the cytoplasmic 5’ to 3’ exoribonuclease, which is conserved among eukaryotic organisms. In Arabidopsis, the 5’ to 3’ exoribonuclease XRN4 is involved in disease resistance, the response to ethylene, RNAi and miRNA-mediated RNA decay. Curiously, XRN4 appears to display selectivity among its substrates because certain 3’ cleavage products formed by miRNA-mediated decay, such as from ARF10 mRNA, accumulate in the xrn4 mutant, whereas others, such as from AGO1, do not. To examine the nature of this selectivity, transcripts that differentially accumulate in xrn4 were identified by combining PARE and Affymetrix arrays. Certain functional categories, such as stamen-associated proteins and hydrolases, were over-represented among transcripts decreased in xrn4, whereas transcripts encoding nuclear-encoded chloroplast-targeted proteins and nucleic acid-binding proteins were over-represented in transcripts increased in xrn4. To ascertain if RNA sequence influences the apparent XRN4 selectivity, a series of chimeric constructs were generated where the miRNA-complementary sites and different portions of the surrounding sequences from AGO1 and ARF10 were interchanged. Analysis of the resulting transgenic plants revealed that the presence of a 150 nucleotide sequence downstream of the ARF10 miRNA-complementary site conferred strong accumulation of the 3’ cleavage products in xrn4. In addition, sequence analysis of differentially accumulating transcripts led to the identification of 27 hexamer motifs that were over-represented in transcripts or miRNA-cleavage products accumulating in xrn4. Taken together, the data indicate that specific mRNA sequences, like those in ARF10, and mRNAs from select functional categories are attractive targets for XRN4-mediated decay. Mixed-stage inflorescences from Col-0 and xrn4-5 plants were harvested. Total RNA was extracted and hybridized to the ATH1 array to determine genes differentially expressed in xrn4-5 compared to Col-0. 2 replicates each.

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Cordycepin time course: Identification of unstable transcripts

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