scholarly journals An active RNA transport mechanism into plant vacuoles

2021 ◽  
Author(s):  
Brice E Floyd ◽  
Zakayo Kazibwe ◽  
Stephanie C Morriss ◽  
Yosia Mugume ◽  
Ang-Yu Liu ◽  
...  
Keyword(s):  
Transport Mechanism ◽  
Atp Hydrolysis ◽  
Rna Degradation ◽  
Rna Transport ◽  
Salvage Pathway ◽  
Transport Pathway ◽  
Transport Pathways ◽  
Plant Vacuole ◽  
Exogenous Addition ◽  
Plant Vacuoles

RNA degradation inside the plant vacuole by the ribonuclease RNS2 is essential for maintaining nucleotide concentrations and cellular homeostasis via the nucleotide salvage pathway. However, the mechanisms by which RNA is transported into the vacuole are not well understood. While selective macroautophagy may contribute to this transport, macroautophagy-independent transport pathways also exist. Here we demonstrate a mechanism for direct RNA transport into vacuoles that is active in purified vacuoles and is ATP hydrolysis-dependent. We identify the RNA helicase SKI2 as a factor required for this transport pathway, as ski2 mutant vacuoles are defective in transport. ski2 mutants have an increased autophagy phenotype that can be rescued by exogenous addition of nucleosides, consistent with a function in nucleotide salvage. This newly-described transport mechanism is therefore critical for RNA degradation, recycling and cytoplasmic nucleotide homeostasis.

scholarly journals Spatial code recognition in neuronal RNA targeting: Role of RNA–hnRNP A2 interactions

2011 ◽  
Vol 194 (3) ◽  
pp. 441-457 ◽  
Author(s):  
Ilham A. Muslimov ◽  
Mihir V. Patel ◽  
Arthur Rose ◽  
Henri Tiedge
Keyword(s):  
Translational Control ◽  
Targeted Delivery ◽  
Fragile X ◽  
Regulation Of Gene Expression ◽  
Rna Transport ◽  
Transport Pathway ◽  
Transport Pathways ◽  
Cgg Repeat ◽  
Rna Targeting ◽  
Nucleotide Interactions

In neurons, regulation of gene expression occurs in part through translational control at the synapse. A fundamental requirement for such local control is the targeted delivery of select neuronal mRNAs and regulatory RNAs to distal dendritic sites. The nature of spatial RNA destination codes, and the mechanism by which they are interpreted for dendritic delivery, remain poorly understood. We find here that in a key dendritic RNA transport pathway (exemplified by BC1 RNA, a dendritic regulatory RNA, and protein kinase M ζ [PKMζ] mRNA, a dendritic mRNA), noncanonical purine•purine nucleotide interactions are functional determinants of RNA targeting motifs. These motifs are specifically recognized by heterogeneous nuclear ribonucleoprotein A2 (hnRNP A2), a trans-acting factor required for dendritic delivery. Binding to hnRNP A2 and ensuing dendritic delivery are effectively competed by RNAs with CGG triplet repeat expansions. CGG repeats, when expanded in the 5′ untranslated region of fragile X mental retardation 1 (FMR1) mRNA, cause fragile X–associated tremor/ataxia syndrome. The data suggest that cellular dysregulation observed in the presence of CGG repeat RNA may result from molecular competition in neuronal RNA transport pathways.

Regulation of RNA helicase activity: principles and examples

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Pascal Donsbach ◽  
Dagmar Klostermeier
Keyword(s):  
Atp Hydrolysis ◽  
Wide Spectrum ◽  
Mrna Translation ◽  
Rna Degradation ◽  
Rna Helicases ◽  
Interaction Partners ◽  
Rna Duplexes ◽  
Self Association

Abstract RNA helicases are a ubiquitous class of enzymes involved in virtually all processes of RNA metabolism, from transcription, mRNA splicing and export, mRNA translation and RNA transport to RNA degradation. Although ATP-dependent unwinding of RNA duplexes is their hallmark reaction, not all helicases catalyze unwinding in vitro, and some in vivo functions do not depend on duplex unwinding. RNA helicases are divided into different families that share a common helicase core with a set of helicase signature motives. The core provides the active site for ATP hydrolysis, a binding site for the non-sequence-specific interactions with RNA, and in many cases a basal unwinding activity. Its activity is often regulated by flanking domains, by interaction partners, or by self-association. In this review, we summarize the regulatory mechanisms that modulate the activities of the helicase core. Case studies on selected helicases with functions in translation, splicing, and RNA sensing illustrate the various modes and layers of regulation in time and space that harness the helicase core for a wide spectrum of cellular tasks.

scholarly journals Multiomics analyses of vesicular transport pathway-specific transcripts and proteins in ovine amnion: responses to altered intramembranous transport

2019 ◽  
Vol 51 (7) ◽  
pp. 267-278 ◽  
Author(s):  
Cecilia Y. Cheung ◽  
Debra F. Anderson ◽  
Robert A. Brace
Keyword(s):  
Energy Metabolism ◽  
Amniotic Fluid ◽  
Intracellular Trafficking ◽  
Cytoplasmic Dynein ◽  
Transport Rate ◽  
Fluid Replacement ◽  
Transport Pathway ◽  
Fetal Sheep ◽  
Transport Pathways ◽  
Fetal Urine

Amniotic fluid volume (AFV) is determined by the rate of intramembranous (IM) transport of amniotic fluid (AF) across the amnion. This transport is regulated by fetal urine-derived stimulators and AF inhibitors. Our objective was to utilize a multiomics approach to determine the IM transport pathways and identify the regulators. Four groups of fetal sheep with experimentally induced alterations in IM transport rate were studied: control, urine drainage (UD), urine drainage with fluid replacement (UDR), and intra-amniotic fluid infusion (IA). Amnion, AF, and fetal urine were subjected to transcriptomics (RNA-Seq) and proteomics studies followed by Ingenuity Pathway Analysis. The analysis uncovered nine transport-associated pathways and four groups of differentially expressed transcripts and proteins. These can be categorized into mediators of vesicular uptake and endocytosis, intracellular trafficking, pathway activation and signaling, and energy metabolism. UD decreased IM transport rate and AFV in conjunction with enhanced expression of vesicular endocytosis regulators but reduced expression of intracellular trafficking mediators. With UDR, IM transport rate decreased and AFV increased. Energy metabolism activators increased while trafficking mediators decreased in expression. IA increased IM transport rate and AFV together with enhanced expressions of vesicular endocytosis and trafficking mediators. We conclude that IM transport across the amnion is regulated by multiple vesicular transcytotic and signaling pathways and that the mediators of intracellular trafficking most likely play an important role in determining the rate of IM transport. Furthermore, the motor protein cytoplasmic dynein light chain-1, which coexpressed in AF and fetal urine, may function as a urine-derived IM transport stimulator.

Na+ and Cl- transport across rabbit nonciliated bronchiolar epithelial (Clara) cells

1989 ◽  
Vol 256 (4) ◽  
pp. C893-C901 ◽  
Author(s):  
M. R. Van Scott ◽  
C. W. Davis ◽  
R. C. Boucher
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Flux Ratio ◽  
Open Circuit ◽  
Clara Cell ◽  
Clara Cells ◽  
Transport Pathway ◽  
Transport Pathways ◽  
Serum Free ◽  
Significant Difference

Radioisotopic flux measurements were performed on rabbit Clara cell epithelium cultured in serum-free hormone-supplemented medium to identify the major ion transport pathways in the cell type. Clara cells cultured in serum-free hormone-supplemented medium exhibit a large short-circuit current compared with cells maintained in serum-containing medium (45 microA/cm2 vs. 15 microA/cm2). The responses to amiloride and isoproterenol, however, are similar for cells grown in the two media. A net amiloride-sensitive movement of Na+ in the mucosal (M)-to-serosal (S) direction undershort- and open-circuit conditions is detected (1.48 and 0.67 mueq.h-1.cm-2, respectively). No statistically significant difference in the unidirectional fluxes of Cl- is apparent in the basal state, but a net flux of Cl- in the S-to-M direction is observed after exposure of the apical membrane to amiloride (0.93 mueq.h-1.cm-2). The partial ionic conductances for Na+ and Cl- estimated from the fluxes measured in the passive directions (JNaS----M, JClM----S) exceed the total tissue conductance by 20%. Ussing flux ratio analyses of Cl- movements at clamped potentials between -60 and +20 mV show that Cl- movements are not strictly through passive conductive pathways at negative potentials. The movement of Cl- can be modeled by passive diffusion combined with Cl- -Cl- exchange equal to 20% of total passive fluxes of Na+ and Cl-. These observations indicate that 1) Na+ absorption is the major active ion transport pathway across cultured Clara cells, 2) active Cl- secretion is minimal in the basal state, and 3) approximately 20% of the unidirectional Cl- fluxes occur via nonconductive pathways.

scholarly journals RNase I regulates Escherichia coli 2′,3′-cyclic nucleotide monophosphate levels and biofilm formation

2018 ◽  
Vol 475 (8) ◽  
pp. 1491-1506 ◽  
Author(s):  
Benjamin M. Fontaine ◽  
Kevin S. Martin ◽  
Jennifer M. Garcia-Rodriguez ◽  
Claire Jung ◽  
Laura Briggs ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Dna Replication ◽  
Cyclic Nucleotide ◽  
Biofilm Formation ◽  
Physiological Role ◽  
Rna Degradation ◽  
Bacterial Biofilm ◽  
Biological Functions ◽  
Salvage Pathway ◽  
E Coli

Regulation of nucleotide and nucleoside concentrations is critical for faithful DNA replication, transcription, and translation in all organisms, and has been linked to bacterial biofilm formation. Unusual 2′,3′-cyclic nucleotide monophosphates (2′,3′-cNMPs) recently were quantified in mammalian systems, and previous reports have linked these nucleotides to cellular stress and damage in eukaryotes, suggesting an intriguing connection with nucleotide/nucleoside pools and/or cyclic nucleotide signaling. This work reports the first quantification of 2′,3′-cNMPs in Escherichia coli and demonstrates that 2′,3′-cNMP levels in E. coli are generated specifically from RNase I-catalyzed RNA degradation, presumably as part of a previously unidentified nucleotide salvage pathway. Furthermore, RNase I and 2′,3′-cNMP levels are demonstrated to play an important role in controlling biofilm formation. This work identifies a physiological role for cytoplasmic RNase I and constitutes the first progress toward elucidating the biological functions of bacterial 2′,3′-cNMPs.

scholarly journals Volume-responsive sodium and proton movements in dog red blood cells.

1984 ◽  
Vol 84 (3) ◽  
pp. 379-401 ◽  
Author(s):  
J C Parker ◽  
V Castranova
Keyword(s):  
Membrane Potential ◽  
Red Blood Cells ◽  
Fluorescent Probe ◽  
Blood Cells ◽  
Indirect Method ◽  
Cell Types ◽  
The Other ◽  
Na Transport ◽  
Transport Pathway ◽  
Transport Pathways

Shrinkage of dog red blood cells (RBC) activates a Na transport pathway that is Cl dependent, amiloride sensitive, and capable of conducting Na-proton counterflow. It is possible to establish transmembrane gradients for either Na or protons and to demonstrate that each cation species can drive reciprocal movements of the other. The nature of the coupling between Na and proton movements was investigated using the fluorescent probe diS-C3(5) and also by an indirect method in which K movements through valinomycin channels were used to draw inferences about the membrane potential. No evidence was found to suggest that the Na-proton pathway activated by shrinkage of dog RBC is a conductive one. By exclusion, it is presumed that the coupling between the counterflow of Na and protons is electroneutral. The volume-activated Na-proton fluxes in dog RBC have certain properties that distinguish them from similar transport pathways in other cell types.

scholarly journals Plastic microbeads from cosmetic products: an experimental study of their hydrodynamic behaviour, vertical transport and resuspension in phytoplankton and sediment aggregates

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Paula Möhlenkamp ◽  
Autun Purser ◽  
Laurenz Thomsen
Keyword(s):  
Plastic Material ◽  
Suspended Sediments ◽  
Physical Characteristics ◽  
Benthic Boundary Layer ◽  
Cosmetic Products ◽  
Transport Pathway ◽  
Transport Pathways ◽  
Waste Products ◽  
Hydrodynamic Behaviour ◽  
Algal Material

Hydrodynamic behaviour and the transport pathways of microplastics within the ocean environment are not well known, rendering accurate predictive models for dispersal management of such pollutants difficult to establish. In the natural environment, aggregation between plastic microbeads and phytodetritus or suspended sediments in rivers and oceans further complicate the patterns of dispersal. In this laboratory study, the physical characteristics and hydrodynamic behaviour of a selection of common plastic microbeads, as used in exfoliation skincare cosmetic products, were investigated. Additionally, the potential for aggregation of these microbeads with phytodetritus and suspended sediments, as well as the subsequent sinking and resuspension behaviour of produced aggregates, were investigated with roller tanks, settling columns and erosion chamber. Physical characteristics of the plastic microbeads showed great heterogeneity, with various densities, sizes and shapes of plastic material being utilised in products designed for the same purpose. The majority of the plastics investigated were positively buoyant in both freshwater and seawater. Aggregation between plastic microbeads and phytoplankton was observed to be swift, with even extremely high concentrations of plastics being rapidly scavenged by suspended algal material. Following aggregation to sizes of 300 to 4400 μm diameter, some formerly buoyant plastics were observed to settle through the water column and enter the benthic boundary layer with settling velocities ranging between 32 and 831 m day–1. These aggregates could be resuspended in the laboratory under critical shear velocities of 0.67–1.33 cm s–1 (free stream velocities of > 10 cm s–1). This rapid aggregation and subsequent settling indicates a potentially important transport pathway for these waste products, a pathway that should be considered when modelling discharge and transport of plastic microbeads and determining the ecosystems that may be at risk from exposure.

scholarly journals Mechanisms and regulation of organic acid accumulation in plant vacuoles

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Xiao-Yu Huang ◽  
Chu-Kun Wang ◽  
Yu-Wen Zhao ◽  
Cui-Hui Sun ◽  
Da-Gang Hu
Keyword(s):  
Organic Acids ◽  
Transport Mechanism ◽  
Regulatory Networks ◽  
Proton Pumps ◽  
Ph Homeostasis ◽  
Complex Processes ◽  
Acid Accumulation ◽  
Plant Vacuoles ◽  
Vacuolar Transport ◽  
Upstream Regulators

AbstractIn fleshy fruits, organic acids are the main source of fruit acidity and play an important role in regulating osmotic pressure, pH homeostasis, stress resistance, and fruit quality. The transport of organic acids from the cytosol to the vacuole and their storage are complex processes. A large number of transporters carry organic acids from the cytosol to the vacuole with the assistance of various proton pumps and enzymes. However, much remains to be explored regarding the vacuolar transport mechanism of organic acids as well as the substances involved and their association. In this review, recent advances in the vacuolar transport mechanism of organic acids in plants are summarized from the perspectives of transporters, channels, proton pumps, and upstream regulators to better understand the complex regulatory networks involved in fruit acid formation.

scholarly journals Long-range transport pathways of tropospheric source gases originating in Asia into the northern lower stratosphere during the Asian monsoon season 2012

2016 ◽  
Author(s):  
Bärbel Vogel ◽  
Gebhard Günther ◽  
Rolf Müller ◽  
Jens-Uwe Grooß ◽  
Armin Afchine ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Asian Monsoon ◽  
Lower Stratosphere ◽  
Monsoon Season ◽  
Transport Pathway ◽  
Transport Pathways ◽  
Air Masses ◽  
Horizontal Transport ◽  
Source Regions ◽  
Subtropical Jet

Abstract. Global simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) using artificial tracers of air mass origin are used to analyze transport pathways from the Asian monsoon region into the lower stratosphere. In a case study, the transport of air masses from the Asian monsoon anticyclone originating in India/China by an eastward migrating anticyclone breaking off from the main anticyclone on 20 September 2012 and filaments separated at the northeastern flank of the anticyclone are analyzed. Enhanced contributions of young air masses (younger than 5 months) are found within the separated anticyclone confined at the top by the thermal tropopause. Further, these air masses are confined by the anticyclonic circulation and at the polar side by the subtropical jet such as the vertical structure looks like a bubble within the upper troposphere. Subsequently, these air masses are transported eastwards along the subtropical jet and enter the lower stratosphere by quasi-horizontal transport in a region of double tropopauses most likely associated with Rossby wave breaking events. As a result, thin filaments with enhanced signatures of tropospheric trace gases are measured in the lower stratosphere over Europe during the TACTS/ESMVal campaign in September 2012 in very good agreement with CLaMS simulations. Our simulations demonstrate that source regions in Asia and in the Pacific Ocean have a significant impact on the chemical composition of the lower stratosphere of the Northern Hemisphere by flooding the extratropical lower stratosphere with young moist air masses in particular at end of the monsoon season in September/October 2012 (up to ~30 % at 380 K) in contrast to the southern hemisphere. End of October 2012, approximately 1.5 ppmv H2O is found in the lower northern hemisphere stratosphere (at 380 K) from source regions in Asia and the tropical Pacific compared to a mean water vapor content of ~5 ppmv. In addition to this main transport pathway from the Asian monsoon anticyclone to the east along the subtropical jet and subsequent transport into the northern lower stratosphere, a second horizontal transport pathway out of the anticyclone to the west into the tropics (TTL) is found in agreement with MIPAS HCFC-22 measurements.

scholarly journals In situ observations of CH<sub>2</sub>Cl<sub>2</sub> and CHCl<sub>3</sub> show efficient transport pathways for very short-lived species into the lower stratosphere via the Asian and North American summer monsoons

2021 ◽  
Author(s):  
Valentin Lauther ◽  
Bärbel Vogel ◽  
Johannes Wintel ◽  
Andrea Rau ◽  
Peter Hoor ◽  
...  
Keyword(s):  
North American ◽  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Late Summer ◽  
Anthropogenic Sources ◽  
North American Monsoon ◽  
Transport Pathway ◽  
Transport Pathways ◽  
Mixing Ratios ◽  
The North

Abstract. Efficient transport pathways for ozone depleting very short-lived substances (VSLS) from their source regions into the stratosphere are a matter of current scientific debate, however they have yet to be fully identified on an observational basis. Understanding the increasing impact of chlorine containing VSLS (Cl-VSLS) on stratospheric ozone depletion is important in order to validate and improve model simulations and future predictions. We report on the first transport study using airborne in situ measurements of the Cl-VSLS dichloromethane (CH2Cl2) and trichloromethane (chloroform, CHCl3) to derive a detailed description of the two most efficient and fast transport pathways from (sub-)tropical source regions into the extratropical lower stratosphere (Ex-LS) in northern hemisphere (NH) late summer. The Cl-VSLS measurements were obtained in the upper troposphere and lower stratosphere (UTLS) above Western Europe and the mid latitude Atlantic Ocean in the frame of the WISE (Wave-driven ISentropic Exchange) aircraft campaign in autumn 2017 and are combined with the results from a three-dimensional simulation of a Lagrangian transport model as well as back-trajectory calculations. Compared to background measurements of similar age we find up to 150 % enhanced CH2Cl2 and up to 100 % enhanced CHCl3 mixing ratios in the Ex-LS. We link the measurements of enhanced mixing ratios to emissions in the region of southern and eastern Asia. Transport from this area to the Ex-LS at potential temperatures in the range of 370–400 K takes about 5–10 weeks via the Asian summer monsoon anticyclone (ASMA). Our measurements suggest anthropogenic sources to be the cause of these strongly elevated Cl-VSLS concentrations observed at the top of the lowermost stratosphere (LMS). A faster transport pathway into the Ex-LS is derived from particularly low CH2Cl2 and CHCl3 mixing ratios in the UTLS. These low mixing ratios reflect weak emission sources and a local seasonal minimum of both species in the boundary layer of Central America and the tropical Atlantic. We show that air masses uplifted by hurricanes, the North American monsoon, and general convection above Central America into the tropical tropopause layer to potential temperatures of about 360–370 K are transported isentropically within 1–5 weeks into the Ex-LS. This transport pathway linked to the North American monsoon mainly impacts the middle and lower part of the LMS with particularly low CH2Cl2 and CHCl3 mixing ratios. In a case study, we specifically analyze air samples directly linked to the uplift by the category 5 hurricane Maria that occurred during October 2017 above the Atlantic Ocean. Regionally differing CHCl3 : CH2Cl2 emission ratios derived from our UTLS measurements suggest a clear similarity between CHCl3 and CH2Cl2 when emitted by anthropogenic sources and differences between the two species mainly caused by additional, likely biogenic, CHCl3 sources. Overall, the transport of strongly enhanced CH2Cl2 and CHCl3 mixing ratios from southern and eastern Asia via the ASMA is the main factor for increasing the chlorine loading from the analyzed VSLS in the Ex-LS during NH late summer. Thus, further increases in Asian CH2Cl2 and CHCl3 emissions, as frequently reported in recent years, will further increase the impact of Cl-VSLS on stratospheric ozone depletion.

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