Project description:We have compared populations of small (21 to 24-nt) RNAs from Arabidopsis immature flowers of WT, drb2 and drb4 mutants and found that DRB2 and DRB4 are needed for the proper biogenesis of polymerase IV-dependent siRNAs
Project description:We have compared populations of small (21 to 24-nt) RNAs from Arabidopsis immature flowers of WT, drb2 and drb4 mutants and found that DRB2 and DRB4 are needed for the proper biogenesis of polymerase IV-dependent siRNAs Examination of small RNA populations from three backgournd: Col0 (WT), drb2 and drb4 mutants
Project description:Arabidopsis thaliana (Arabidopsis) encodes five DOUBLE-STRANDED RNA BINDING (DRB) proteins, DRB1 to DRB5, that predominantly act as non-catalytic cofactors for DICER-LIKE (DCL) proteins in the double-stranded RNA (dsRNA) processing stages of small RNA (sRNA) production pathways. In the nucleus, DRB1 is required for microRNA (miRNAs) processing from imperfectly dsRNA precursors by DCL1. Similarly, DRB4 is required by DCL4 for small-interfering RNAs (siRNAs) production from endogenous or exogenous perfectly dsRNA templates. DRB2 has been recently demonstrated to be required for miRNA and siRNA production in developmentally-important tissues of Arabidopsis while the requirement of either DRB3 or DRB5 in sRNA production remains unclear. Here, we analyse in parallel, the contribution of all five DRB protein family members to the global sRNA landscape of Arabidopsis floral tissues. In depth bioinformatic analysis of sRNA sequencing datasets generated from floral tissues of DRB knockout mutant (drb) plant lines, drb1, drb2, drb4, drb12, drb14, drb24, and drb35 and their comparison to the floral sRNA profile of wild-type Arabidopsis, has enabled confident assignment of the requirement of DRB1, DRB2 and DRB4 for the production of specific miRNA and siRNA subclasses in this tissue. Our analyses have additionally identified novel and/or expanded roles for DRB2 in miRNA, trans-acting siRNAs (tasiRNAs) and natural antisense transcript siRNAs (natsiRNAs) production.
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
Project description:Comparison of the endogenous small RNA content of Arabidopsis flower bud tissue: wild type vs. mutants in polIV pathways Keywords: High throughput 454 small RNA sequencing.
Project description:Using a crucifer-infecting strain of Tobacco Mosaic Virus (TMV-Cg) and Arabidopsis thaliana as a model system, we analyzed the viral small RNA profile in wild-type plants as well as rdr mutants by applying small RNA deep sequencing technology. Over 100,000 TMV-Cg-specific small RNA reads, mostly of 21- (78.4%) and 22-nucleotide (12.9%) in size and originating predominately (79.9%) from the genomic sense RNA strand, were captured at an early infection stage, yielding the first high-resolution small RNA map for a plant virus. The TMV-Cg genome harbored multiple, highly reproducible small RNA-generating hot spots that corresponded to regions with no apparent local hairpin-forming capacity. Significantly, both the rdr1 and rdr6 mutants exhibited globally reduced levels of viral small RNA production as well as reduced strand bias in viral small RNA population, revealing an important role for these host RDRs in viral siRNA biogenesis. In addition, an informatics analysis showed that a large set of host genes could be potentially targeted by TMV-Cg-derived siRNAs for posttranscriptional silencing, raising the interesting possibility for a hidden layer of widespread virus-host interactions that may contribute to viral pathogenicity and host specificity.