MiRNAs target conserved motifs of diverse genes encoding NB-LRRs to trigger trans-acting siRNAs in legumes.
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ABSTRACT:
ORGANISM(S): Phaseolus vulgaris Medicago truncatula Glycine max Arachis hypogaea
PROVIDER: GSE31061 | GEO | 2011/10/24
SECONDARY ACCESSION(S): PRJNA146213
REPOSITORIES: GEO
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Project description:Trans-acting siRNAs (tasiRNAs) negatively regulate target transcripts and are characterized by siRNAs spaced in 21-nucleotide 'phased' intervals. TasiRNAs have not been extensively described in many plant species. We identified dozens of new miRNAs in Medicago and soybean and confirmed 119 Medicago targets. A search for phased tasiRNA-like small RNAs ('phasiRNAs') found at least 114 Medicago loci, the majority of which were NB-LRR encoding genes. Notably, conserved domains in NB-LRR-encoding RNAs are targeted by several 22-nt miRNA families to trigger phasiRNA production. DCL2 and SGS3 transcripts were also cleaved by these 22-nt miRNAs, generating phased small RNAs, suggesting synchronization between silencing and pathogen defense pathways. A second example of 'two-hit' phasiRNA processing was identified, utilizing miR156-miR172 sites. Our data illustrate a complex tasiRNA-mediated regulatory circuit that potentially modulates plant-microbe interactions. A few miRNA triggers regulate an extremely large gene family by targeting highly conserved protein motif-encoding sequences, representing a new paradigm for miRNA function. Examination of different tissue types in legumes (Medicago, soybean, common bean, peanut) by high throughput sequencing for small RNA profiling
2011-10-24 | E-GEOD-31061 | biostudies-arrayexpress
Project description:Small RNAs are a class of noncoding RNAs which are of great importance in gene expression regulatory networks. Different families of small RNAs are generated via distinct biogenesis pathways. One such family specific to plants is that of phased, secondary siRNAs (phasiRNAs); these require RDR6, DCL4, and microRNA (miRNA) trigger for their biogenesis. Protein-encoding genes are an important source of phasiRNAs. The model legume Medicago truncatula generates phasiRNAs from many PHAS loci, and we aimed to investigate their biogenesis and mechanism by which miRNAs trigger these molecules. We modulated miRNA abundances in transgenic tissues showing that the abundance of phasiRNAs correlates with the levels of both miRNA triggers and the target, precursor transcripts. We identified sets of phasiRNAs or PHAS loci that predominantly and substantially increase in response to miRNA overexpression. In the process of validating targets from miRNA overexpression tissues, we found that in the miRNA-mRNA target pairing, the 3’ terminal nucleotide (the 22nd position), but not the 10th position, is important for phasiRNA production. Mutating the single 3’ terminal nucleotide dramatically diminishes phasiRNA production. Ectopic expression of Medicago NB-LRR-targeting miRNAs in Arabidopsis showed that only a few NB-LRRs are capable of phasiRNA production; our data indicate that this is due to target inaccessibility determined by sequences flanking target sites. We propose that target accessibility is an important component of miRNA-target interactions that could be utilized in target prediction, and the evolution of mRNA sequences flanking miRNA target sites may be impacted.
2015-06-20 | GSE67613 | GEO
Project description:Small RNAs, including microRNAs (miRNAs) and small interfering RNAs (siRNAs) are negative regulators to target endogenous genes and repetitive sequences in plants. Although miRNAs and trans-acting or phased siRNAs (tasiRNAs or phasiRNAs) were found to target hundreds of disease related genes in Medicago, their role in plant-pathogen interactions in the legumes, particularly the R genes mediated interaction of soybean and the pathogen Phytophthora sojae is poorly understood. A deep sequencing was performed on nine soybean near isogenic lines (NILs) each carrying an Rps (Resistance to Phytophthora sojae) gene and their recurrent parent “Williams”, with sampling performed both pre- and post-inoculation with P. sojae. From these data, 44 known MIRNA loci with new miRNA variants, 78 novel miRNAs corresponding to 108 precursors, and 208 phasiRNA-producing (PHAS) loci were identified. Our data showed that overall the expression levels of miRNAs, phasiRNAs and siRNAs were extensively down-regulated after pathogen-inoculation. Moreover, the down-regulation levels in the nine resistant NILs were significantly higher than that detected in the susceptible Williams, and variations of small RNA expression within the resistant NILs were also observed, suggesting the molecular responses of different Rps lines are distinct. Surprisingly, the expression level changes of 21-nt phasiRNAs were significantly positively correlated with that of the corresponding mRNA level of the PHAS genes, suggesting the cascade effects of miRNA triggers on the downstream PHAS genes and phasiRNAs. Our data provided a comprehensive picture regarding small RNA based regulation of target genes, particularly NB-LRRs, involved in the responses to the pathogen. 20 samples were sequenced, 10 inoculated with P. sojae, the other 10 were mock-inoculated
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Project description:Maize LEAFBLADELESS1 (LBL1) and Arabidopsis SUPPRESSOR OF GENE SILENCING3 (SGS3) play orthologous roles in the biogenesis of 21 nucleotide trans-acting short-interfering RNAs (tasiRNAs). The phenotypes conditioned by mutation of lbl1 and SGS3 are, however, strikingly different, suggesting that the activities of these small RNA biogenesis components, or the tasiRNAs and their targets might not be entirely conserved. To investigate the basis for this phenotypic variation, we compared the small RNA content between wild-type and lbl1 seedling apices. We show that LBL1 affects all major classes of small RNAs, and reveal unexpected crosstalk between tasiRNA biogenesis and other small RNA pathways regulating miRNAs, retrotransposons, and DNA transposons. We further identified genomic regions generating phased siRNAs, including numerous loci generating 22-nt phased small RNAs from long hairpin RNAs or overlapping antisense transcripts not previously described in other plant species. By combining both analyses, we identified nine TAS loci, all belonging to the conserved TAS3 family. Contrary to other plant species, no TAS loci targeted by a single miRNA were identified. Information from target prediction, RNAseq, and PARE analyses identified the tasiARFs as the major functional tasiRNAs in the maize vegetative apex where they regulate expression of ARF3 homologs. As such, divergence in TAS pathways is unlikely to account for the distinct phenotypes of tasiRNA biogenesis mutants in Arabidopsis and maize. Instead, the data suggests variation in the spatiotemporal regulation of ARF3, or divergence in its function, as a plausible basis for the dramatic phenotypic differences observed upon mutation of SGS3/lbl1 in Arabidopsis and maize. An analysis of tasiRNA biogenesis, activity, and contribution to developmental phenotypes in the maize leaf. Data generated includes small RNA sequencing data and mRNA sequencing data. All data was generated in both wild type and lbl1 mutant maize leaf apices. Three replicates were generated for each genotype for the small RNA data. Two of these replicates were also used for the RNA-seq data.
2014-11-20 | E-GEOD-50557 | biostudies-arrayexpress
Project description:Maize LEAFBLADELESS1 (LBL1) and Arabidopsis SUPPRESSOR OF GENE SILENCING3 (SGS3) play orthologous roles in the biogenesis of 21 nucleotide trans-acting short-interfering RNAs (tasiRNAs). The phenotypes conditioned by mutation of lbl1 and SGS3 are, however, strikingly different, suggesting that the activities of these small RNA biogenesis components, or the tasiRNAs and their targets might not be entirely conserved. To investigate the basis for this phenotypic variation, we compared the small RNA content between wild-type and lbl1 seedling apices. We show that LBL1 affects all major classes of small RNAs, and reveal unexpected crosstalk between tasiRNA biogenesis and other small RNA pathways regulating miRNAs, retrotransposons, and DNA transposons. We further identified genomic regions generating phased siRNAs, including numerous loci generating 22-nt phased small RNAs from long hairpin RNAs or overlapping antisense transcripts not previously described in other plant species. By combining both analyses, we identified nine TAS loci, all belonging to the conserved TAS3 family. Contrary to other plant species, no TAS loci targeted by a single miRNA were identified. Information from target prediction, RNAseq, and PARE analyses identified the tasiARFs as the major functional tasiRNAs in the maize vegetative apex where they regulate expression of ARF3 homologs. As such, divergence in TAS pathways is unlikely to account for the distinct phenotypes of tasiRNA biogenesis mutants in Arabidopsis and maize. Instead, the data suggests variation in the spatiotemporal regulation of ARF3, or divergence in its function, as a plausible basis for the dramatic phenotypic differences observed upon mutation of SGS3/lbl1 in Arabidopsis and maize.
2014-11-20 | GSE50557 | GEO
Project description:Small RNAs, including microRNAs (miRNAs) and small interfering RNAs (siRNAs) are negative regulators to target endogenous genes and repetitive sequences in plants. Although miRNAs and trans-acting or phased siRNAs (tasiRNAs or phasiRNAs) were found to target hundreds of disease related genes in Medicago, their role in plant-pathogen interactions in the legumes, particularly the R genes mediated interaction of soybean and the pathogen Phytophthora sojae is poorly understood. A deep sequencing was performed on nine soybean near isogenic lines (NILs) each carrying an Rps (Resistance to Phytophthora sojae) gene and their recurrent parent “Williams”, with sampling performed both pre- and post-inoculation with P. sojae. From these data, 44 known MIRNA loci with new miRNA variants, 78 novel miRNAs corresponding to 108 precursors, and 208 phasiRNA-producing (PHAS) loci were identified. Our data showed that overall the expression levels of miRNAs, phasiRNAs and siRNAs were extensively down-regulated after pathogen-inoculation. Moreover, the down-regulation levels in the nine resistant NILs were significantly higher than that detected in the susceptible Williams, and variations of small RNA expression within the resistant NILs were also observed, suggesting the molecular responses of different Rps lines are distinct. Surprisingly, the expression level changes of 21-nt phasiRNAs were significantly positively correlated with that of the corresponding mRNA level of the PHAS genes, suggesting the cascade effects of miRNA triggers on the downstream PHAS genes and phasiRNAs. Our data provided a comprehensive picture regarding small RNA based regulation of target genes, particularly NB-LRRs, involved in the responses to the pathogen.
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Project description:Phased, secondary siRNAs (phasiRNAs) represent a class of small RNAs in plants generated via distinct biogenesis pathways, predominantly dependent on the activity of 22 nt miRNAs. Most 22 nt miRNAs are processed by DCL1 from miRNA precursors containing an asymmetric bulge, yielding a 22/21 nt miRNA/miRNA* duplex. Here we show that miR1510, a soybean miRNA capable of triggering phasiRNA production from numerous NB-LRRs, previously described as 21 nt in its mature form, primarily accumulates as a 22 nt isoform via monouridylation. We demonstrate that in Arabidopsis, this uridylation is performed by HESO1. Biochemical experiments showed that the 3' terminus of miR1510 is only partially 2'-O-methylated, because of the terminal mispairing in the miR1510/miR1510* duplex that inhibits HEN1 activity in soybean. miR1510 emerged in the Phaseoleae ~41 to 42 MYA with a conserved precursor structure yielding a 22 nt monouridylated form, yet a variant in mung bean is processed directly in a 22 nt mature form. This analysis of miR1510 yields two observations: (1) plants can utilize post-processing modification to generate abundant 22 nt miRNA isoforms to more efficiently regulate target mRNA abundances; (2) comparative analysis demonstrates an example of selective optimization of precursor processing of a young plant miRNA.
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2015-06-17 | E-GEOD-69348 | biostudies-arrayexpress
Project description:The use of syn-tasiRNAs has been proposed as an RNA interference technique alternative to those previously described: hairpin based, virus induced gene silencing or artificial miRNAs. In this study we engineered the TAS1c locus to impair Plum pox virus (PPV) infection by replacing the five native siRNAs with two 210-bp fragments from the CP and the 3´NCR regions of the PPV genome. Deep sequencing analysis of the small RNA species produced by both constructs in planta has shown that phased processing of the syn-tasiRNAs is construct-specific. While in syn-tasiR-CP construct the processing was as predicted 21-nt phased in register with miR173-guided cleavage, the processing of syn-tasiR-3NCR is far from what was expected. A 22-nt species from the miR173-guided cleavage was a guide of two series of phased small RNAs, one of them in an exact 21-nt register, and the other one in a mixed of 21-/22-nt frame. In addition, both constructs produced abundant PPV-derived small RNAs in the absence of miR173 as a consequence of a strong sense PTGS induction. The antiviral effect of both constructs was also evaluated in the presence or absence of miR173 and showed that the impairment of PPV infection was not significantly higher when miR173 was present. The results show that syn-tasiRNAs processing depends on construct-specific factors that should be further studied before the so-called MIGS (miRNA-induced gene silencing) technology can be used reliably.
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