Loss of RNA–Dependent RNA Polymerase 2 (RDR2) Function Causes Widespread and Unexpected Changes in the Expression of Transposons, Genes, and 24-nt Small RNAs

Transposable elements (TEs) comprise a substantial portion of many eukaryotic genomes and are typically transcriptionally silenced. RNA–dependent RNA polymerase 2 (RDR2) is a component of the RNA–directed DNA methylation (RdDM) silencing pathway. In maize, loss of mediator of paramutation1 (mop1) encoded RDR2 function results in reactivation of transcriptionally silenced Mu transposons and a substantial reduction in the accumulation of 24 nt short-interfering RNAs (siRNAs) that recruit RNA silencing components. An RNA–seq experiment conducted on shoot apical meristems (SAMs) revealed that, as expected based on a model in which RDR2 generates 24 nt siRNAs that suppress expression, most differentially expressed DNA TEs (78%) were up-regulated in the mop1 mutant. In contrast, most differentially expressed retrotransposons (68%) were down-regulated. This striking difference suggests that distinct silencing mechanisms are applied to different silencing templates. In addition, >6,000 genes (24% of analyzed genes), including nearly 80% (286/361) of genes in chromatin modification pathways, were differentially expressed. Overall, two-thirds of differentially regulated genes were down-regulated in the mop1 mutant. This finding suggests that RDR2 plays a significant role in regulating the expression of not only transposons, but also of genes. A re-analysis of existing small RNA data identified both RDR2–sensitive and RDR2–resistant species of 24 nt siRNAs that we hypothesize may at least partially explain the complex changes in the expression of genes and transposons observed in the mop1 mutant

The influence of music on health and life,

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Coherent and tunable THz source,

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Industrial integration of high coherence tunable single frequency semiconductor lasers based on VECSEL technology for scientific instrumentation in NIR and MIR

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The HD spectrum near 2.3μm by CRDS-VECSEL: Electric quadrupole transition and collision-induced absorption

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Endogenous transposable elements associated with virus infection in maize

Evidence that transposable DNA elements are ubiquitous in plants and that gross genetic instability may well provide the means for rapid evolutionary and even regulatory adaptation is rapidly accumulating. McClintock (1984) has suggested, for example, that stress in various forms might stimulate genome reorganization and the activation of transposable elements. Such a response would be analogous to, but much less specific than, the cascade of repair and recombination functions that is induced by DNA damage in Escherichia coli and is known as the SOS response. One possible source of such stress is systemic virus infection in plants. Although the symptoms of virus infection are generally not heritable, several studies have suggested that virally stressed plants may suffer unusual levels of genetic aherations. This notion is based mainly on genetic studies of virus-infected maize (Sprague et al. 1963; Sprague and McKinney 1966, 1971; Mottinger et al. 1984a) and earlier studies on..

Highly coherent phase-lock of an 8.1 μ m quantum cascade laser to a turn-key mid-IR frequency comb

International audienceA continuous-wave Fabry–Pérot quantum cascade laser (QCL) emitting at 8.1 μm operating in the single mode regime has been coherently phase locked to a turn-key low-noise commercial mid-Infrared (mid-IR) optical frequency comb. The stability of the comb used as a reference is transferred to the QCL resulting in an integrated residual phase error of 0.4 rad. The laser linewidth is narrowed by more than two orders of magnitude reaching sub-kHz level at 1 ms observation time, limited by the spectral purity of the mid-IR comb. Our experiment is an important step toward the development of both powerful and metrology-grade QCLs and fully stabilized QCL frequency comb and opens perspectives for precision measurements and frequency metrology in the mid-IR

Low-noise III-V metasurface based semiconductor vortex laser and rotational Doppler velocimetry

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