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Comprehensive investigation of miRNAs enhanced by analysis of sequence variants, expression patterns, AGO loading and target cleavage

ABSTRACT: MicroRNAs (miRNAs) are a class of small RNAs which typically function by guiding cleavage of target messenger RNAs. They have been shown to play major roles in a variety of plant processes including development, and responses to pathogens and environmental stresses. To identify new miRNAs and regulation in Arabidopsis thaliana, 27 small RNA libraries were constructed and sequenced from various tissues, stresses and small RNA biogenesis mutants, resulting in 95 million genome-matched sequences. The use of rdr2 to enrich the miRNA population greatly enhanced this analysis and led to the discovery of 44 new miRNAs arising from both known and new precursors. Parallel Analysis of RNA Ends (PARE) data provide evidence that the majority guide target cleavage. The inclusion of novel stress/tissue conditions, such as submergence-stressed flowers, enabled identification of new stress regulation of both miRNAs and their targets, all of which were validated in wild type plants. By combining small RNA expression analysis with ARGONAUTE (AGO) immunoprecipitation data and global target cleavage data from PARE, a much more complete picture of Arabidopsis miRNAs was obtained. This combinatorial approach led to the discovery of AGO loading and target cleavage biases, which gave important insights into tissue-specific expression patterns, pathogen responses and the role of sequence variation among closely related miRNA family members.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE44622 | GEO | 2013/12/31

SECONDARY ACCESSION(S): PRJNA190673

REPOSITORIES: GEO

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Project description:MicroRNAs (miRNAs) are a class of small RNAs which typically function by guiding cleavage of target messenger RNAs. They have been shown to play major roles in a variety of plant processes including development, and responses to pathogens and environmental stresses. To identify new miRNAs and regulation in Arabidopsis thaliana, 27 small RNA libraries were constructed and sequenced from various tissues, stresses and small RNA biogenesis mutants, resulting in 95 million genome-matched sequences. The use of rdr2 to enrich the miRNA population greatly enhanced this analysis and led to the discovery of 44 new miRNAs arising from both known and new precursors. Parallel Analysis of RNA Ends (PARE) data provide evidence that the majority guide target cleavage. The inclusion of novel stress/tissue conditions, such as submergence-stressed flowers, enabled identification of new stress regulation of both miRNAs and their targets, all of which were validated in wild type plants. By combining small RNA expression analysis with ARGONAUTE (AGO) immunoprecipitation data and global target cleavage data from PARE, a much more complete picture of Arabidopsis miRNAs was obtained. This combinatorial approach led to the discovery of AGO loading and target cleavage biases, which gave important insights into tissue-specific expression patterns, pathogen responses and the role of sequence variation among closely related miRNA family members. Examination of various tissues, stresses and small RNA biogenesis mutants in Arabidopsis by high-throughput sequencing for small RNA profiling. We have used AGO-IP and PARE data from the published data, which were downloaded from NCBI GEO with the following accession number. AGO-IP from GSM253622, GSM707682, GSM642335, GSM642336, GSM512703, GSM512702, GSM707683, GSM707684, GSM707685, GSM149080, GSM253623, GSM304283, GSM642337, GSM642338, GSM253624, GSM415788, GSM707686, GSM707687, GSM707688, GSM707689, GSM415787, GSM149081, GSM253625, GSM415789, GSM415790, GSM304285, GSM415791, GSM415792 PARE sequencing data from xrn4 flowers were obtained from Gene Expression Omnibus with accession number GSM280227.

Project description:MicroRNAs are important regulatory molecules in most eukaryotes and the identification of their mRNA targets is essential for their functional analysis. From inflorescence tissue of Arabidopsis, >28,000,000 signatures were sequenced from 5’ ends of polyadenylated products of mRNA decay. Within the set of ~27,000 transcripts included in the 3,500,000 non-redundant signatures, several previously predicted but non-validated miRNA targets were found. Like validated targets, most showed a single abundant signature at the miRNA cleavage site, particularly in libraries from a mutant deficient in the 5’ to 3’ exonuclease AtXRN4. Among the most unexpected miRNA targets discovered were miRNA precursor transcripts that are self-targeted by their own mature miRNA. Although the miRNAs of Arabidopsis have been extensively investigated, working in reverse from the cleaved targets, additional novel miRNAs were identified and validated. This deep and versatile approach will impact the study of other aspects of RNA processing beyond miRNA-target RNA pair analyses. Keywords: miRNA-target RNA pairs, Palallel analysis of RNA ends, PARE, SBS RNA from inflorescence tissue from wildtype Arabidopsis and xrn4 mutants was extracted. Following polyA RNA extraction, libraries for PARE were constructed. RNA from inflorescence tissue from wildtype Arabidopsis (Col-0), and rdr2 and dcl2,3,4 mutants was extracted. The material was submitted to Illumina and libraries were constructed for small RNAs. Individual small RNA libraries from inflorescences of Arabidopsis wildtype, rdr2, and dcl2/dcl3/dcl4 were sequenced with SBS at Illumina, Inc. The distribution of small RNA sizes in each library is in agreement with that published previously for the wild type or the respective mutants sequenced with MPSS or 454; however, the presence and abundances of some small RNAs may differ. This may be attributed to the use of different sequencing technologies with different depths, biological differences in the tissue used, or other unknown reasons. raw data requested but not provided for GSM280226 and GSM280227

Project description:Background: Since the proposal of Brachypodium distachyon as a model for the grasses over 500 Bdi-miRNAs have been annotated in miRBase making Brachypodium second in number only to rice. Other monocots, such as switchgrass, are completely absent from the miRBase database. While a significant number of miRNAs have been identified which are highly conserved across plants, little research has been done with respect to the conservation of miRNA targets. Plant responses to abiotic stresses are regulated by diverse pathways many of which involve miRNAs; however, it can be difficult to identify miRNA guided gene regulation when the miRNA is not the primary regulator of the target mRNA. Results: To investigate miRNA target conservation and stress response involvement, a set of PARE (Parallel Analysis of RNA Ends) libraries totaling over 2 billion reads was constructed and sequenced from Brachypodium, switchgrass, and sorghum representing the first public release of degradome data from the latter two species. Analysis of this data provided not only PARE evidence for miRNA guided cleavage of over 7,000 predicted target mRNAs in Brachypodium, but also evidence for miRNA guided cleavage of over 1,000 homologous transcripts in sorghum and switchgrass. A pipeline was constructed to compare RNA-seq and PARE data made from Brachypodium plants exposed to various abiotic stress conditions. This resulted in the identification of 44 miRNA targets which exhibit stress regulated cleavage. Time course experiments were performed to reveal the relationship between miR393ab, miR169a, miR394ab, and their respective targets throughout the first 36 hours of the cold stress response in Brachypodium. Conclusions: Knowledge gained from this study provides considerable insight into the degradomes and the breadth of miRNA target conservation among these three species. Additionally associations of a number of miRNAs and target mRNAs with the stress responses have been revealed which will aid researchers in developing stress tolerant transgenic crops.

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Comprehensive investigation of miRNAs enhanced by analysis of sequence variants, expression patterns, AGO loading and target cleavage

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