Project description:Brassinosteroids (BRs) are a class of class of phytohormones with important roles in regulating physiological and developmental processes. Small RNAs, including small interfering RNAs and microRNAs (miRNAs), are non-protein coding RNAs that regulate gene expression at the transcriptional and post-transcriptional levels. However, the roles of small RNAs in BR response have not been studied well. In this study, we aimed to identify BR-responsive small RNA clusters and miRNAs in Arabidopsis. In addition, the effect of BR-responsive small RNAs on their transcripts and target genes were examined. Small RNA libraries were constructed from control and epibrassinolide-treated seedlings. After sequencing the small RNA libraries, differentially expressed small RNA clusters were identified by examining the expression levels of small RNAs in 100-nt bins of Arabidopsis genome. To identify the BR-responsive miRNAs, the expression levels of all the annotated mature miRNAs, registered in miRBase, were analyzed. Previously published RNA-seq data were utilized to monitor the BR-responsive expression patterns of differentially expressed small RNA clusters and miRNA target genes. In results, 38 BR-responsive small RNA clusters, including 30 down-regulated and eight up-regulated clusters, were identified. These differentially expressed small RNA clusters were from miRNA loci, transposons, protein-coding genes, pseudo genes and others. Of these, a transgene, BRI1, accumulates small RNAs, which are not found in the wild type. Small RNAs in this transgene are up-regulated by BRs while BRI1 mRNA is down-regulated by BRs. By analyzing the expression patterns of mature miRNAs, we have identified BR-repressed miR398a-5p and BR-induced miR156g. Although miR398a-5p is down-regulated by BRs, its predicted targets were not responsive to BRs. However, SPL3, a target of BR-inducible miR156g, is down-regulated by BRs. BR-responsive small RNAs and miRNAs identified in this study will provide an insight into the role of small RNAs in BR responses in plants. Especially, we suggest that miR156g/SPL3 module might play a role in BR-mediated growth and development in Arabidopsis.
Project description:Secondary metabolites are involved in the plant stress response. Among these are scopolin and its active form scopoletin, which are coumarin derivatives associated with reactive oxygen species scavenging and pathogen defence. Here we show that in Arabidopsis thaliana, scopolin accumulation can be induced in the root by osmotic stress and in the leaf by low temperature stress. A genetic screen for altered scopolin levels in Arabidopsis thaliana identified a mutant compromised for scopolin accumulation in response to stress; the lesion was present in a homologue of THO1, the product of which contributes to the THO/TREX complex. The THO/TREX complex contributes to RNA silencing, supposedly by trafficking precursors of small RNAs. Mutants carrying defective THO and RDR6 genes were impaired with respect to scopolin accumulation in response to stress, suggesting a mechanism based on RNA silencing like the transacting small interfering RNA pathway which requires THO/TREX and RDR6 function.
Project description:Low-oxygen stress associated with natural phenomena such as waterlogging, results in widespread transcriptome changes and a metabolic switch from aerobic respiration to anaerobic fermentation. High-throughput sequencing of small RNA libraries obtained from low-oxygen stressed and control root tissue identified a total of 65 unique microRNA (miRNA) sequences from 46 families, and 14 trans-acting small interfering RNA (tasiRNA) from 3 families. Low-oxygen stress resulted in changes to the abundance of 46 miRNAs from 19 families, and all 3 tasiRNA families. Chemical inhibition of mitochondrial respiration caused similar changes in expression in a majority of the low-oxygen responsive small RNAs analysed. Our data indicate that miRNAs and tasiRNAs play a role in gene regulation and possibly developmental responses to low oxygen, and that a major signal for these responses is likely to be dependent on mitochondrial function. Keywords: Small RNA transcriptome analysis
Project description:Small RNA sequences from Arabidopsis thaliana Col-0 inflorescence tissues of three biological replicates. The data were analyzed to identify non-templated nucleotides in Arabidopsis small RNAs.
Project description:The Arabidopsis genome contains a highly complex and abundant population of small RNAs, and many of the endogenous siRNAs are dependent on RNA-DEPENDENT RNA POLYMERASE 2 (RDR2) for their biogenesis. By analyzing an rdr2 loss-of-function mutant using two different parallel sequencing technologies, MPSS and 454, we characterized the complement of miRNAs expressed in Arabidopsis inflorescence to considerable depth. Nearly all known miRNAs were enriched in this mutant and we identified 13 new miRNAs, all of which were relatively low abundance and constitute new families. Trans-acting siRNAs (ta-siRNAs) were even more highly enriched. Computational and gel blot analyses suggested that the minimal number of miRNAs in Arabidopsis is approximately 155. The size profile of small RNAs in rdr2 reflected enrichment of 21-nt miRNAs and other classes of siRNAs like ta-siRNAs, and a significant reduction in 24-nt heterochromatic siRNAs. Other classes of small RNAs were found to be RDR2-independent, particularly those derived from long inverted repeats and a subset of tandem repeats. The small RNA populations in other Arabidopsis small RNA biogenesis mutants were also examined; a dcl2/3/4 triple mutant showed a similar pattern to rdr2, whereas dcl1-7 and rdr6 showed reductions in miRNAs and ta-siRNAs consistent with their activities in the biogenesis of these types of small RNAs. Deep sequencing of mutants provides a genetic approach for the dissection and characterization of diverse small RNA populations and the identification of low abundance miRNAs. Keywords: small RNA sequences generated by 454 sequencing