Abstract Mobile genetic elements threaten genome integrity in all organisms. MUT-2/RDE-3 is a ribonucleotidyltransferase required for transposon silencing and RNA interference (RNAi) in C. elegans . When tethered to RNAs in heterologous expression systems, RDE-3 can add long stretches of alternating non-templated uridine (U) and guanosine (G) ribonucleotides to the 3’ termini of these RNAs (polyUG or pUG tails). Here, we show that, in its natural context in C. elegans , RDE-3 adds pUG tails to transposon RNAs, as well as to targets of RNAi. pUG tails with more than 16 perfectly alternating 3’ U and G nucleotides convert otherwise inert RNA fragments into agents of gene silencing. pUG tails promote gene silencing by recruiting RNA-dependent RNA Polymerases (RdRPs), which use pUG-tailed RNAs as templates to synthesize small interfering RNAs (siRNAs). Cycles of pUG RNA-templated siRNA synthesis and siRNA-directed mRNA pUGylation underlie dsRNA-directed transgenerational epigenetic inheritance in the C. elegans germline. Our results show that pUG tails convert RNAs into transgenerational memories of past gene silencing events, which, we speculate, allow parents to inoculate progeny against the expression of unwanted or parasitic genetic elements.
Urban air traffic has gradually attracted attention in recent years, which will bring endless vitality to future urban development. An objective and accurate method of assessing vertiport capacity is the basis for the air traffic flow management of UAVs, which plays an important role in improving the efficiency of urban airspace resources. First of all, this paper establishes a theoretical capacity calculation model for ground facilities such as takeoff and landing platforms, taxiways and aprons, respectively. Next, this paper analyzes the service characteristics of each ground facility and establishes different types of UAV queuing systems to obtain UAV delay curves based on a UAV Poisson flow arrival model. Subsequently, a suitable acceptable delay level is selected to obtain the corresponding UAV flow, which means the actual capacity of UAV operations. Eventually, the validity of the model is verified through actual drone data arithmetic examples. The calculation results show that the combination of “1 landing + 2 takeoffs” can achieve better capacity results and that the landing platform is more prone to congestion than the takeoff platform. Change in average service time has the greatest impact on the apron capacity, and the takeoff platform is the most sensitive to changes in the acceptable delay level.
Abstract Summary A critical aspect for exploring the biological function of a microRNA (miRNA) lies on exact detection and validation of its target mRNAs. However, no convenient and efficient web-based server is available for plant biologists to identify the experimentally verified target mRNAs of miRNAs. In this work, we built a comprehensive web-based platform for miRNA–target analysis, named as Whole-degradome-based Plant MiRNA–target Interaction Analysis Server (WPMIAS), for validation of predicted interactions of miRNAs and their target mRNAs (MTIs) by user-submitted data or all available pre-loaded degradome data. Besides, the server can construct degradome-based miRNA regulatory networks (MRNs) based on the validated MTIs to help study the functions and relations among miRNAs and target mRNAs. WPMIAS is also suitable for other small RNAs (sRNAs), such as 21-nt phased siRNAs and natural antisense siRNAs, which direct cleavage of target mRNAs. Currently, WPMIAS supports 68 plant species with 189 cDNA and 271 pre-loaded plant degradome datasets. The user can identify all validated MTIs by analyzing all degradome data at a time and understand when and where MTIs take place and their cleavage levels. With the data obtained from WPMIAS, the user can build a plant miRNA–target map, where it is convenient to find interesting research ideas on miRNAs. In summary, WPMIAS is able to support a comprehensive web-based plant miRNA–target analysis and expected to greatly promote future research on plant miRNAs. Availability and implementation It can be freely accessed at https://cbi.njau.edu.cn/WPMIAS/. Supplementary information Supplementary data are available at Bioinformatics online.
Phased siRNAs (phasiRNAs) are a class of small interfering RNAs (siRNAs) which play essential roles in plant development and defence. However, only a few phasiRNAs have been extensively studied due to the difficulties in identifying and characterizing plant phasiRNAs by plant biologists. Herein, we describe a comprehensive and multi-functional web server termed PhasiRNAnalyzer, which is able to identify all crucial components in plant phasiRNA's regulatory pathway (phase-initiator→PHAS gene→phasiRNA cluster→target gene). Currently, PhasiRNAnalyzer exhibits the following advantages: I) It is the most comprehensive platform which hosts 170 plant species with 256 genome data, 438 cDNA data and 271 degradome data. II) It can identify all crucial components in phasiRNA's regulatory pathway, and verify the interactions between phasiRNAs and their target genes based on degradome data. III) It can perform differential expression analysis of phasiRNAs on each PHAS gene locus between different samples conveniently. IV) It provides the user-friendly interfaces and introduces several improvements, primarily by making more accurate and efficient analysis when dealing with deep sequencing data. In summary, PhasiRNAnalyzer is a comprehensive and systemic phasiRNA analysis server with high sensitivity and efficiency. It can be freely accessed at https://cbi.njau.edu.cn/PPSA/.
In order to improve the performance of traditional particle swarm optimization, this paper introduces the principle of Levy flight and cross-border reset mechanism. In the proposed par ...
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