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Novel DICER-LIKE1 siRNAs Bypass the Requirement for DICER-LIKE4 in Maize Development

ABSTRACT: Dicer enzymes function at the core of RNA silencing to defend against exogenous RNA, or as an endogenous mechanism of gene regulation. Plant DICER-LIKE4 (DCL4) performs dual functions, acting in antiviral defense, as well as in development via the biogenesis of tasiR-ARFs. These small RNAs play an essential role in the grasses and act to spatially define the expression domain of AUXIN RESPONSE FACTOR3 (ARF3) transcription factors. However, contrary to tasiR-ARFs’ essential function in development, DCL4 proteins exhibit strong evidence of recurrent adaptation typical of host factors involved in antiviral immunity. Here, we address how DCL4 balances its role in development with pressures to diversify in response to viral attack. We show that, in contrast to other tasiR-ARF biogenesis mutants, dcl4 null alleles condition an uncharacteristically mild phenotype, correlated with normal expression of select arf3 targets. Loss of DCL4 activity yields a class of 22-nt tasiR-ARF variants associated with the processing of arf3 transcripts into 22-nt secondary siRNAs by DCL1. Our findings uncover the presence of a novel DCL1-dependent siRNA pathway that bypasses the otherwise adverse developmental effects of DCL4 mutations. This novel pathway is predicted to have important implications for DCL4’s role in antiviral defense by reducing the selective constraints on DCL4 and allowing it to diversify in response to viral suppressors.

ORGANISM(S): Zea mays

PROVIDER: GSE66986 | GEO | 2015/09/01

SECONDARY ACCESSION(S): PRJNA278637

REPOSITORIES: GEO

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Novel DICER-LIKE1 siRNAs Bypass the Requirement for DICER-LIKE4 in Maize Development

Project description:Dicer enzymes function at the core of RNA silencing to defend against exogenous RNA, or as an endogenous mechanism of gene regulation. Plant DICER-LIKE4 (DCL4) performs dual functions, acting in antiviral defense, as well as in development via the biogenesis of tasiR-ARFs. These small RNAs play an essential role in the grasses and act to spatially define the expression domain of AUXIN RESPONSE FACTOR3 (ARF3) transcription factors. However, contrary to tasiR-ARFs’ essential function in development, DCL4 proteins exhibit strong evidence of recurrent adaptation typical of host factors involved in antiviral immunity. Here, we address how DCL4 balances its role in development with pressures to diversify in response to viral attack. We show that, in contrast to other tasiR-ARF biogenesis mutants, dcl4 null alleles condition an uncharacteristically mild phenotype, correlated with normal expression of select arf3 targets. Loss of DCL4 activity yields a class of 22-nt tasiR-ARF variants associated with the processing of arf3 transcripts into 22-nt secondary siRNAs by DCL1. Our findings uncover the presence of a novel DCL1-dependent siRNA pathway that bypasses the otherwise adverse developmental effects of DCL4 mutations. This novel pathway is predicted to have important implications for DCL4’s role in antiviral defense by reducing the selective constraints on DCL4 and allowing it to diversify in response to viral suppressors. Examination of small RNAs isolated from dcl4, dcl1 and double mutants in imbibed kernels of maize

2015-09-01 | E-GEOD-66986 | biostudies-arrayexpress

Dicer-like proteins and their role in plant-herbivore interactions in Nicotiana attenuata

Project description:DICER-like proteins produce small RNAs that silence genes involved in development and defenses against viruses and pathogens. Which DCLs participate in plant-herbivore interactions remains unstudied. We identified four distinct DCL genes and stably silenced their expression by RNAi in Nicotiana attenuata, a model system for the study of plant-herbivore interactions. Silencing DCL1 expression was lethal to the plants. Manduca sexta larvae performed significantly better on ir-dcl3and ir-dcl4 plants, but not on ir-dcl2 plants compared to wild type plants. Phytohormones, defense metabolites and microarray analyses revealed that when DCL3 and DCL4 were silenced separately, herbivore resistance traits were regulated in distinctly different ways. Crossing of the lines revealed complex interactions in the patterns of regulation. Single ir-dcl4 and double ir-dcl2/ ir-dcl3 plants were impaired in JA accumulation, while JA-Ile was increased in ir-dcl3 plants. Ir-dcl3 and ir-dcl4 plants were impaired in nicotine accumulation; silencing DCL2 in combination with either DCL3 or DCL4 restored nicotine levels to those of WT. Trypsin proteinase inhibitor activity and transcripts were only silenced in ir-dcl3 plants. We conclude that DCL2/3/4 interact in a complex manner to regulate anti-herbivore defenses and that these interactions significantly complicate the already challenging task of understanding smRNA function in the regulation of biotic interactions.

2013-12-24 | GSE30124 | GEO

Dicer-like proteins and their role in plant-herbivore interactions in Nicotiana attenuata

2013-12-24 | E-GEOD-30124 | biostudies-arrayexpress

Cross-species comparative analysis of Dicer proteins during Sindbis virus infection

Project description:The role of RNA silencing as a defense mechanism against viruses remains to be formerly established in mammalian somatic cells. Here, we determined the antiviral properties of human and Drosophila Dicer proteins in a heterologous setup. We expressed human Dicer (hDicer) in Drosophila, and Drosophila Dicer-2 in human cells, and measured the impact on the response to Sindbis virus (SINV) infection. In flies, hDicer presents a low processing activity, but partially rescues a Dcr2 null mutation in flies. Expression of Dicer-2 in HEK293 cells allows the processing of SINV RNA into 21-nt-long small RNAs. Nevertheless, instead of conferring a protective effect against SINV, Dicer-2 expression increases viral replication in HEK293 cells. We present evidence that this effect is due to a competition with the interferon pathway. Our results therefore suggest that adding functionial RNA silencing machinery in IFN-competent differentiated mammalian cells can be detrimental for antiviral defense.

2015-12-28 | GSE62934 | GEO

Characterization of DCL4 missense alleles provides novel insights into its ability to process distinct classes of dsRNA substrates

Project description:In the model plant Arabidopsis thaliana, four Dicer-like proteins (DCL1-4) mediate the production of various classes of small RNAs (sRNAs). Among these four proteins, DCL4 is by far the most versatile RNaseIII-like enzyme and previously identified dcl4 missense alleles were shown to uncouple the production of the various classes of DCL4-dependent sRNAs. Yet, little is known about the molecular mechanism pertaining this uncoupled production. Here, by studying the subcellular localization, interactome and binding to the sRNA precursors of three distinct dcl4 missense alleles, we simultaneously highlight the absolute requirement of its helicase domain for efficient production of all DCL4-dependent sRNAs, and identify an important determinant of DCL4 versatility within its PAZ domain that is mandatory for efficient processing of intramolecular foldback dsRNA precursors but dispensable for the production of siRNAs from RDR-dependent dsRNA susbtrates. This study not only provides novel insights into DCL4 mode of action in plants but also delineates interesting tools to further study the complexity of plant RNA silencing pathways.

2018-04-24 | GSE106383 | GEO

Plants encode a general siRNA suppressor that is induced and suppressed by viruses

Project description:Small RNAs play essential regulatory roles in genome stability, development and stress responses in most eukaryotes. Plants encode DICER-LIKE (DCL) RNaseIII enzymes, including DCL1, which produces miRNAs, and DCL2, DCL3 and DCL4, which produce diverse size classes of siRNA. Plants also encode RNASE THREE-LIKE (RTL) enzymes that lack DCL-specific domains and whose function is largely unknown. Small RNA sequencing in plants over-expressing RTL1 or RTL2 or lacking RTL2 revealed that RTL1 over-expression inhibits the accumulation of all types of small RNAs produced by DCL2, DCL3 and DCL4, indicating that RTL1 is a general suppressor of plant siRNA pathways. By contrast, RTL2 plays minor, if any, role in the small RNA repertoire. In vivo and in vitro assays revealed that RTL1 prevents siRNA production by degrading dsRNA before they are processed by DCL2, DCL3 and DCL4. The substrate of RTL1 cleavage is likely long perfect (or near-perfect) dsRNA, consistent with the RTL1-insensitivity of miRNAs, which derive from short imperfect dsRNA. RTL1 is naturally expressed only weakly in roots, but virus infection strongly induces its expression in leaves, suggesting that RTL1 induction is a general strategy used by viruses to counteract the siRNA-based plant antiviral defense. Accordingly, transgenic plants over-expressing RTL1 are more sensitive to TYMV infection than wild-type plants, likely because RTL1 prevents the production of antiviral siRNAs. However, TCV, TVCV and CMV, which encode stronger suppressors of RNA silencing (VSR) than TYMV, are insensitive to RTL1 over-expression. Indeed, TCV VSR inhibits RTL1 activity, suggesting that inducing RTL1 expression and dampening RTL1 activity is a dual strategy used by viruses to establish a successful infection. These results reveal another level of complexity in the evolutionary battle between viruses and plant defenses. Flower sRNA profiles in diverse conditions involving RTL1 and RTL2

2013-09-10 | E-GEOD-49866 | biostudies-arrayexpress

The helicase domain of human Dicer prevents RNAi-independent activation of antiviral and inflammatory pathways

Project description:In mammalian somatic cells, the relative contribution of RNAi and the type I interferon response during viral infection is unclear. The apparent inefficiency of antiviral RNAi might be due to self-limiting properties and mitigating co-factors of the key enzyme Dicer. In particular, the helicase domain of human Dicer appears to be an important restriction factor of its activity. Here, we study the involvement of several helicase-truncated mutants of human Dicer in the antiviral response. All deletion mutants display a PKR-dependent antiviral phenotype against certain viruses, and one of them, Dicer N1, acts in a completely RNAi-independent manner. Transcriptomic analyses show that many genes from the interferon and inflammatory response pathways are upregulated in Dicer N1-expressing cells. We show that some of these genes are controlled by NF-kB and that blocking this pathway abrogates the antiviral phenotype of Dicer N1. Our findings highlight the crosstalk between Dicer, PKR, and the NF-kB pathway, and suggest that human Dicer may have repurposed its helicase domain to prevent basal activation of antiviral and inflammatory pathways.

2024-01-26 | GSE241798 | GEO

The helicase domain of human Dicer prevents RNAi-independent activation of antiviral and inflammatory pathways

2024-01-26 | GSE241797 | GEO

The helicase domain of human Dicer prevents RNAi-independent activation of antiviral and inflammatory pathways

2024-01-26 | GSE241796 | GEO

An isoform of Dicer protects mammalian stem cells against multiple RNA viruses

Project description:In mammals, early resistance to viruses relies on interferons, which protect differentiated but not stem cells from viral replication. Many other organisms rely instead on RNA interference (RNAi) mediated by a specialised Dicer protein that cleaves viral double stranded RNA. Whether RNAi also contributes to mammalian antiviral immunity remains controversial. Here we identify an isoform of Dicer, named antiviral Dicer (aviD), that protects tissue stem cells from RNA viruses, including Zika virus and SARS-CoV-2, by dicing viral double-stranded RNA to orchestrate antiviral RNAi. Our work sheds light on the molecular regulation of antiviral RNAi in mammalian innate immunity in which different cell-intrinsic antiviral pathways are tailored to the differentiation status of cells.

2021-07-09 | GSE173946 | GEO

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