Project description:MicroRNAs (miRNAs) are 21-24 nucleotide (nt) small non-coding RNAs that regulate a wide variety of biological processes at the posttranscriptional level. MiRNA expression often exhibits spatial and temporal specificity. However, genome-wide miRNA expression patterns in different Arabidopsis organs during plant development have not yet been fully investigated. In this study, we sequenced 59 small RNA libraries generated from different tissue types at different developmental stages of Arabidopsis. We then re-annotated Arabidopsis miRNAs based on the most recent criteria. Global analysis of miRNA expression patterns showed that most miRNAs are ubiquitously expressed in different organs or tissues. But a small set of miRNAs, either previously annotated or newly identified, show highly specific expression patterns. In addition, the expression of some miRNA members belonging to the same family is strictly regulated spatially and temporally. Unexpectedly, we found that quite a few miRNAs are produced from different arms of their hairpin precursors at different developmental stages, suggesting that arm switching could be a general and important mechanism in developmental regulation.
Project description:Purpose: Circadian clock in plants temporally coordinates biological processes throughout the day synchronizing gene expression with environmental changes. Here, we examined the genome-wide circadian and diurnal control of Arabidopsis transcriptome using high throughout RNA-seq approach. Methods: Transcriptional and posttranscritional profiles were identified and characterized for Arabidopsis seedlings grown under continuous light or long-day condition (16 h light/8 h dark) for one day (each condition has two biological replicates). Results: We show that rhythmic posttranscriptional regulation is also a significant factor for genome-wide profile of circadian plant transcriptome. Two major posttranscriptioal mechanisms alternative splicing (AS) and alternative polyadenylation (APA) show circadian rhythmicity, resulting from the oscillation in the genes invovled in AS and APA. Conclusions: Arabidopsis circadian clock not only controls the transcription of genes, but also affects their posttranscriptional regulation through regulating AS and APA.
Project description:Arabidopsis microRNA expression regulation was studied in a wide array of abiotic stresses such as drought, heat, salinity, copper excess/deficiency, cadmium excess and sulphur deficiency. A home-built RT-qPCR mirEX platform for the amplification of 289 Arabidopsis microRNA transcripts was used to study their response to abiotic stresses. Small RNA sequencing and Northern hybridization were performed to study the expression of mature microRNAs. In the case of common climate change related stresses such as drought, heat and salinity we observed broad induction of the level of primary miRNAs that was not observed at the level of microRNAs.. In the case of local soil pollution stresses, that are represented by heavy metal contaminations or deprivation of a specific micro- or macroelement, the transcriptional response of pri-miRNAs was quite limited but also not predictive to the level of the mature microRNA. This points to an essential role of posttranscriptional regulation of microRNAs expression. We found that the level of several microRNAs can be differentially regulated in early and late response to stress. New Arabidopsis microRNAs responsive to abiotic stresses were discovered. Three microRNAs: miR319a/b, miR319b.2, and miR400 have been found to be responsive in several abiotic stresses and thus can be regarded as a general stress-responsive microRNA species. Additionally, a new target for miR319b.2 – TBL10 has been experimentally confirmed. However, its level under different abiotic stresses is unchanged in comparison to control conditions. In the promoter region of the TBL10 gene we found the presence of many stress-responsive elements. We suggest that transcriptional induction resulting in the increase of transcript levels is downregulated by the increase of the miR319b.2 ultimately resulting in a stable level of TBL10 mRNA. Our experiments show the existence of a complex regulatory network involved in the microRNA level control that is necessary to fine-tune plant response to environmental cues.
Project description:Plant microRNAs (miRNAs) have been implicated in plant immunity. These mainly focusing Arabidopsis thaliana threatened by (hemi-)biotrophic pathogens such as the bacterial pathogen Pseudomonas syringae. Here, we show that the Arabidopsis miRNA pathway is important for defense responses against the necrotrophic fungus Alternaria brassicicola. The miRNA pathway mutant ago1 exhibits an exaggerated response when treated with A. brassicicola, proposing that AGO1 is positive regulator. We found a subset of Arabidopsis miRNAs that quickly change their expression and their abundance in AGO1 complexes in plants exposed to A. brassicicola. The miRNAs responding to pathogen treatment are mainly targeting genes encoding metabolic enzymes, proteins involved protein degradation or transposons. In case of miR163, A. brassicicola infection results in increased levels of miRNA precursors and preferential accumulation of an unspliced form of pri-miR163, suggesting that A. brassicicola infection changes the transcriptional and post-regulation of pri-miRNAs. miR163 acts as a negative regulator of plant defense because mir163 mutants are more resistant when treated with A. brassicicola. Taken together, our results reveal the existence of positively and negatively acting Arabidopsis miRNA modulating the defense responses against A. brassicicola and highlight the importance of host miRNAs in the interaction between plants and necrotrophic pathogens.
Project description:microRNAs (miRNA’s) regulation target gene expression, often transcription factors and as such control entire transcriptional networks. This control is important for various developmental transitions and stress responses in a wide range of eukaryotic organisms. While miRNA-mediated gene regulation has been investigated over time (temporal) and in whole organs or tissues in multiple different organisms highlighting their importance, there has been a distinct lack of focus on spatial resolution of miRNA biology. Here we present at cell-type specific resolution, miRNA loading and miRNA action within the Arabidopsis root. Our results for the first time demonstrate the multiple novel modes of miRNA action and illustrate the widespread nature of miRNA movement, at a genome scale within a complex eukaryotic organ.
Project description:deOliveiraDalMolin2010 - Genome-scale
metabolic network of Arabidopsis thaliana (AraGEM)
This model is described in the article:
AraGEM, a genome-scale
reconstruction of the primary metabolic network in
Arabidopsis.
de Oliveira Dal'Molin CG, Quek LE,
Palfreyman RW, Brumbley SM, Nielsen LK.
Plant Physiol. 2010 Feb; 152(2):
579-589
Abstract:
Genome-scale metabolic network models have been successfully
used to describe metabolism in a variety of microbial organisms
as well as specific mammalian cell types and organelles. This
systems-based framework enables the exploration of global
phenotypic effects of gene knockouts, gene insertion, and
up-regulation of gene expression. We have developed a
genome-scale metabolic network model (AraGEM) covering primary
metabolism for a compartmentalized plant cell based on the
Arabidopsis (Arabidopsis thaliana) genome. AraGEM is a
comprehensive literature-based, genome-scale metabolic
reconstruction that accounts for the functions of 1,419 unique
open reading frames, 1,748 metabolites, 5,253 gene-enzyme
reaction-association entries, and 1,567 unique reactions
compartmentalized into the cytoplasm, mitochondrion, plastid,
peroxisome, and vacuole. The curation process identified 75
essential reactions with respective enzyme associations not
assigned to any particular gene in the Kyoto Encyclopedia of
Genes and Genomes or AraCyc. With the addition of these
reactions, AraGEM describes a functional primary metabolism of
Arabidopsis. The reconstructed network was transformed into an
in silico metabolic flux model of plant metabolism and
validated through the simulation of plant metabolic functions
inferred from the literature. Using efficient resource
utilization as the optimality criterion, AraGEM predicted the
classical photorespiratory cycle as well as known key
differences between redox metabolism in photosynthetic and
nonphotosynthetic plant cells. AraGEM is a viable framework for
in silico functional analysis and can be used to derive new,
nontrivial hypotheses for exploring plant metabolism.
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