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Small RNA profiling reveals regulation of Arabidopsis miR168 and heterochromatic siRNA415 in response to fungal elicitors.

ABSTRACT: BACKGROUND: Small RNAs (sRNAs), including small interfering RNAs (siRNAs) and microRNAs (miRNAs), have emerged as important regulators of eukaryotic gene expression. In plants, miRNAs play critical roles in development, nutrient homeostasis and abiotic stress responses. Accumulating evidence also reveals that sRNAs are involved in plant immunity. Most studies on pathogen-regulated sRNAs have been conducted in Arabidopsis plants infected with the bacterial pathogen Pseudomonas syringae, or treated with the flagelin-derived elicitor peptide flg22 from P. syringae. This work investigates sRNAs that are regulated by elicitors from the fungus Fusarium oxysporum in Arabidopsis. RESULTS: Microarray analysis revealed alterations on the accumulation of a set of sRNAs in response to elicitor treatment, including miRNAs and small RNA sequences derived from massively parallel signature sequencing. Among the elicitor-regulated miRNAs was miR168 which regulates ARGONAUTE1, the core component of the RNA-induced silencing complex involved in miRNA functioning. Promoter analysis in transgenic Arabidopsis plants revealed transcriptional activation of MIR168 by fungal elicitors. Furthermore, transgenic plants expressing a GFP-miR168 sensor gene confirmed that the elicitor-induced miR168 is active. MiR823, targeting Chromomethylase3 (CMT3) involved in RNA-directed DNA methylation (RdDM) was also found to be regulated by fungal elicitors. In addition to known miRNAs, microarray analysis allowed the identification of an elicitor-inducible small RNA that was incorrectly annotated as a miRNA. Studies on Arabidopsis mutants impaired in small RNA biogenesis demonstrated that this sRNA, is a heterochromatic-siRNA (hc-siRNA) named as siRNA415. Hc-siRNAs are known to be involved in RNA-directed DNA methylation (RdDM). SiRNA415 is detected in several plant species. CONCLUSION: Results here presented support a transcriptional regulatory mechanism underlying MIR168 expression. This finding highlights the importance of miRNA functioning in adaptive processes of Arabidopsis plants to fungal infection. The results of this study also lay a foundation for the involvement of RdDM processes through the activity of siRNA415 and miR823 in mediating regulation of immune responses in Arabidopsis plants.

SUBMITTER: Baldrich P

PROVIDER: S-EPMC4299684 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Small RNA profiling reveals regulation of Arabidopsis miR168 and heterochromatic siRNA415 in response to fungal elicitors.

Baldrich Patricia P Kakar Klementina K Siré Christelle C Moreno Ana Beatriz AB Berger Angélique A García-Chapa Meritxell M López-Moya Juan José JJ Riechmann José Luis JL San Segundo Blanca B

BMC genomics 20141210

<h4>Background</h4>Small RNAs (sRNAs), including small interfering RNAs (siRNAs) and microRNAs (miRNAs), have emerged as important regulators of eukaryotic gene expression. In plants, miRNAs play critical roles in development, nutrient homeostasis and abiotic stress responses. Accumulating evidence also reveals that sRNAs are involved in plant immunity. Most studies on pathogen-regulated sRNAs have been conducted in Arabidopsis plants infected with the bacterial pathogen Pseudomonas syringae, or ...[more]

PMID: 25491154

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Project description:BACKGROUND: Heterochromatin is the tightly packaged dynamic region of the eukaryotic chromosome that plays a vital role in cellular processes such as mitosis and meiotic recombination. Recent experiments in Schizosaccharomyces pombe have revealed the structure of centromeric heterochromatin is affected in RNAi pathway mutants. It has also been shown in fission yeast that the heterochromatin barrier is traversed by RNA Pol II and that the passage of RNA Pol II through heterochromatin is important for heterochromatin structure. Thus, an intricate interaction between the RNAi machinery and RNA Pol II affects heterochromatin structure. However, the role of the RNAi machinery and RNA Pol II on the metazoan heterochromatin landscape is not known. This study analyses the interaction of the small RNA machinery and RNA Pol II on Drosophila heterochromatin structure. RESULTS: The results in this paper show genetic and biochemical interaction between RNA Pol II (largest and second largest subunit) and small RNA silencing machinery components (dcr-2, ago1, ago2, piwi, Lip [D], aub and hls). Immunofluorescence analysis of polytene chromosomes from trans-heterozygotes of RNA Pol II and different mutations of the small RNA pathways show decreased H3K9me2 and mislocalization of Heterochromatin protein-1. A genetic analysis performed on these mutants showed a strong suppression of white-mottled4h position effect variegation. This was further corroborated by a western blot analysis and chromatin immunoprecipitation, which showed decreased H3K9me2 in trans-heterozygote mutants compared to wild type or single heterozygotes. Co-immunoprecipitation performed using Drosophila embryo extracts showed the RNA Pol II largest subunit interacting with Dcr-2 and dAGO1. Co-localization performed on polytene chromosomes showed RNA Pol II and dAGO1 overlapping at some sites. CONCLUSION: Our experiments show a genetic and biochemical interaction between RNA Pol II (largest and second largest subunits) and the small RNA silencing machinery in Drosophila. The interaction has functional aspects in terms of determining H3K9me2 and HP-1 deposition at the chromocentric heterochromatin. Thus, RNA Pol II has an important role in establishing heterochromatin structure in Drosophila.

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Small RNA profiling reveals regulation of Arabidopsis miR168 and heterochromatic siRNA415 in response to fungal elicitors.

Publications

Small RNA profiling reveals regulation of Arabidopsis miR168 and heterochromatic siRNA415 in response to fungal elicitors.

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