The Experts below are selected from a list of 4017 Experts worldwide ranked by ideXlab platform
Emmanuel P. Dinnat - One of the best experts on this subject based on the ideXlab platform.
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IGARSS - Sea Surface Salinity Retrievals from Aquarius Using Neural Networks
IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium, 2019Co-Authors: Yan Soldo, David M. Le Vine, Emmanuel P. DinnatAbstract:Even though the Sea Surface Salinity (SSS) retrieved from Aquarius are generally very close to in-situ measurements, the level of similarity varies with the region and with the circumstances of the observations (wind speed, sea surface temperature, etc.). SSS is currently retrieved from the brightness temperatures measured by Aquarius and applying the current theoretical model for the propagation and emission of the natural thermal radiation. In this contribution we consider an alternative retrieval approach based on a Neural Network (NN) with the goal of improving the subsets of Aquarius SSS data that are in poorer agreement with in-situ measurements. The subset considered here are the SSS retrieved at latitudes higher than 30˚. The output of the NN approach are compared against in-situ measurements using four statistical metrics (correlation coefficient, bias, RMSD and 5% trimmed range). The output of the NN and the nominal Aquarius SSS are compared against SSS values from in-situ measurements and from ocean models. From these comparisons it appears that the output of the NN matches the in-situ measurements better than the nominal Aquarius SSS.
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Status of Aquarius and Salinity Continuity
Remote Sensing, 2018Co-Authors: David M. Le Vine, Frank J. Wentz, Thomas Meissner, Emmanuel P. Dinnat, Gary LagerloefAbstract:Aquarius is an L-band radar/radiometer instrument combination that has been designed to measure ocean salinity. It was launched on 10 June 2011 as part of the Aquarius/SAC-D observatory. The observatory is a partnership between the United States National Aeronautics and Space Agency (NASA), which provided Aquarius, and the Argentinian space agency, Comisiόn Nacional de Actividades Espaciales (CONAE), which provided the spacecraft bus, Satelite de Aplicaciones Cientificas (SAC-D). The observatory was lost four years later on 7 June 2015 when a failure in the power distribution network resulted in the loss of control of the spacecraft. The Aquarius Mission formally ended on 31 December 2017. The last major milestone was the release of the final version of the salinity retrieval (Version 5). Version 5 meets the mission requirements for accuracy, and reflects the continuing progress and understanding developed by the science team over the lifetime of the mission. Further progress is possible, and several issues remained unresolved at the end of the mission that are relevant to future salinity retrievals. The understanding developed with Aquarius is being transferred to radiometer observations over the ocean from NASA’s Soil Moisture Active Passive (SMAP) satellite, and salinity from SMAP with accuracy approaching that of Aquarius are already being produced.
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Aquarius Final Release Product and Full Range Calibration of L-Band Radiometers
IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018Co-Authors: Emmanuel P. Dinnat, David Le Vine, Liang HongAbstract:Aquarius final product V5.0 has been released. The dataset includes close to four years of global radiometric measurements at L-band. The mission's objective was to monitor sea surface salinity, but other applications of its data over land and the cryosphere have been developed. For this reason, it is important to have accurate calibration over the full range of antenna temperatures from natural targets. It is also needed in order to combine Aquarius measurements with other L-band sensors. Aquarius calibration is strongly focused on the ocean. We present a research product which is part of the final release and aims at producing an accurate calibration from the low end (celestial sky) to the high end (land and ice) of the brightness temperature scale. We calibrate the Aquarius radiometers using measurements over the Sky and oceans and assess the new calibration using measurements over land.
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IGARSS - Aquarius Final Release Product and Full Range Calibration of L-Band Radiometers
IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018Co-Authors: Emmanuel P. Dinnat, David M. Le Vine, Liang HongAbstract:Aquarius final product V5.0 has been released. The dataset includes close to four years of global radiometric measurements at L-band. The mission's objective was to monitor sea surface salinity, but other applications of its data over land and the cryosphere have been developed. For this reason, it is important to have accurate calibration over the full range of antenna temperatures from natural targets. It is also needed in order to combine Aquarius measurements with other L-band sensors. Aquarius calibration is strongly focused on the ocean. We present a research product which is part of the final release and aims at producing an accurate calibration from the low end (celestial sky) to the high end (land and ice) of the brightness temperature scale. We calibrate the Aquarius radiometers using measurements over the Sky and oceans and assess the new calibration using measurements over land.
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Status of Aquarius Salinity
2018 IEEE 15th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment (MicroRad), 2018Co-Authors: David Le Vine, Gary Lagerloef, Thomas Meissner, Emmanuel P. Dinnat, Liang Hong, Frank J. WentzAbstract:Aquarius, an L-band radar/radiometer instrument combination designed to measure ocean salinity. It was launched June 10, 2011 as part of the Aquarius/SAC-D observatory, a partnership between NASA, which provided Aquarius, and the Argentine space agency (CONAE) which provided the spacecraft bus, SAC-D. The observatory was lost four years later on June 7, 2015 when a failure in the power distribution network resulted in loss of control of the spacecraft. The Aquarius Mission formally ended December 31, 2017. The last major milestone was the release of the Project's final version of the salinity retrieval (Version 5.0). Version 5.0 meets the Mission requirements for accuracy and reflects the continuing progress and understanding developed by the Science Team over the lifetime of the mission.
P. De Matthaeis - One of the best experts on this subject based on the ideXlab platform.
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Radio Frequency Interference (RFI) Products on the Aquarius Website
IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018Co-Authors: P. De Matthaeis, D. Le M. Vine, Y. Soida, V. TsontosAbstract:Aquarius has produced maps of salinity by measuring Earth's natural emissions at L-band. However, measurements made by its instruments are affected by the presence of Radio Frequency Interference (RFI). For this reason, RFI detection algorithms had been implemented, both for the radiometer and the scatterometer, in order to reduce the impact of RFI on science data. In an effort to improve understanding of L-band RFI, the Aquarius mission has generated a new series of products. This contribution presents how these products were produced as well as the information that they contain. These products will be available starting at the end of January 2018 on the Aquarius website.
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IGARSS - Radio Frequency Interference (RFI) Products on the Aquarius Website
IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018Co-Authors: P. De Matthaeis, D.m. Le Vine, Y. Soida, V. TsontosAbstract:Aquarius has produced maps of salinity by measuring Earth's natural emissions at L-band. However, measurements made by its instruments are affected by the presence of Radio Frequency Interference (RFI). For this reason, RFI detection algorithms had been implemented, both for the radiometer and the scatterometer, in order to reduce the impact of RFI on science data. In an effort to improve understanding of L-band RFI, the Aquarius mission has generated a new series of products. This contribution presents how these products were produced as well as the information that they contain. These products will be available starting at the end of January 2018 on the Aquarius website.
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Aquarius status and recent results
Radio Science, 2014Co-Authors: D. Le M. Vine, P. De Matthaeis, S. Abraham, G.s.e Lagerloef, Emmanuel P. Dinnat, C. UtkuAbstract:Aquarius is a combination active/passive instrument at L band designed to map sea surface salinity globally from space. The radiometer (passive) is the primary instrument for retrieving salinity, and the scatterometer (active) provides information to correct for a major source of error, sea surface roughness (waves). In addition, the radiometer includes a number of special features designed to meet the goal for this challenging measurement, including measurement of the third Stokes parameter to help with the correction for Faraday rotation and rapid sampling to help with the mitigation of radio frequency interference. Aquarius was launched on 10 June 2011 aboard the Aquarius/SAC-D observatory and has been working well. The salinity retrieval continues to improve, and the special features suggest the potential for new applications of remote sensing from space at L band.
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Aquarius Active/Passive RFI Environment at L-Band
IEEE Geoscience and Remote Sensing Letters, 2014Co-Authors: D.m. Le Vine, P. De MatthaeisAbstract:Active/Passive instrument combinations (i.e., radiometer and radar) are being developed at L-band for remote sensing of sea surface salinity and soil moisture. Aquarius is already in orbit and SMAP is planned for launch in the Fall of 2014. Aquarius has provided for the first time a simultaneous look at the Radio Frequency Interference (RFI) environment from space for both active and passive instruments. The RFI environment for the radiometer observations is now reasonably well known and examples from Aquarius are presented in this manuscript that show that RFI is an important consideration for the scatterometer as well. In particular, extensive areas of the USA, Europe and Asia exhibit strong RFI in both the radiometer band at 1.41 GHz and in the band at 1.26 GHz employed by the Aquarius scatterometer. Furthermore, in areas such as the USA, where RFI at 1.4 GHz is relatively well controlled, RFI in the scatterometer band maybe the limiting consideration for the operation of combination active/passive instruments.
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Aquarius active passive rfi environment at l band
IEEE Geoscience and Remote Sensing Letters, 2014Co-Authors: D. Le M. Vine, P. De MatthaeisAbstract:Active/Passive instrument combinations (i.e., radiometer and radar) are being developed at L-band for remote sensing of sea surface salinity and soil moisture. Aquarius is already in orbit and SMAP is planned for launch in the Fall of 2014. Aquarius has provided for the first time a simultaneous look at the Radio Frequency Interference (RFI) environment from space for both active and passive instruments. The RFI environment for the radiometer observations is now reasonably well known and examples from Aquarius are presented in this manuscript that show that RFI is an important consideration for the scatterometer as well. In particular, extensive areas of the USA, Europe and Asia exhibit strong RFI in both the radiometer band at 1.41 GHz and in the band at 1.26 GHz employed by the Aquarius scatterometer. Furthermore, in areas such as the USA, where RFI at 1.4 GHz is relatively well controlled, RFI in the scatterometer band maybe the limiting consideration for the operation of combination active/passive instruments.
Gary Lagerloef - One of the best experts on this subject based on the ideXlab platform.
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Status of Aquarius and Salinity Continuity
Remote Sensing, 2018Co-Authors: David M. Le Vine, Frank J. Wentz, Thomas Meissner, Emmanuel P. Dinnat, Gary LagerloefAbstract:Aquarius is an L-band radar/radiometer instrument combination that has been designed to measure ocean salinity. It was launched on 10 June 2011 as part of the Aquarius/SAC-D observatory. The observatory is a partnership between the United States National Aeronautics and Space Agency (NASA), which provided Aquarius, and the Argentinian space agency, Comisiόn Nacional de Actividades Espaciales (CONAE), which provided the spacecraft bus, Satelite de Aplicaciones Cientificas (SAC-D). The observatory was lost four years later on 7 June 2015 when a failure in the power distribution network resulted in the loss of control of the spacecraft. The Aquarius Mission formally ended on 31 December 2017. The last major milestone was the release of the final version of the salinity retrieval (Version 5). Version 5 meets the mission requirements for accuracy, and reflects the continuing progress and understanding developed by the science team over the lifetime of the mission. Further progress is possible, and several issues remained unresolved at the end of the mission that are relevant to future salinity retrievals. The understanding developed with Aquarius is being transferred to radiometer observations over the ocean from NASA’s Soil Moisture Active Passive (SMAP) satellite, and salinity from SMAP with accuracy approaching that of Aquarius are already being produced.
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Assessment of Aquarius Sea Surface Salinity
Remote Sensing, 2018Co-Authors: Gary Lagerloef, Oleg Melnichenko, Thomas Meissner, Peter HackerAbstract:Aquarius was the first NASA satellite to observe the sea surface salinity (SSS) over the global ocean. The mission successfully collected data from 25 August 2011 to 7 June 2015. The Aquarius project released its final version (Version-5) of the SSS data product in December 2017. The purpose of this paper is to summarize the validation results from the Aquarius Validation Data System (AVDS) and other statistical methods, and to provide a general view of the Aquarius SSS quality to the users. The results demonstrate that Aquarius has met the mission target measurement accuracy requirement of 0.2 psu on monthly averages on 150 km scale. From the triple point analysis using Aquarius, in situ field and Hybrid Coordinate Ocean Model (HYCOM) products, the root mean square errors of Aquarius Level-2 and Level-3 data are estimated to be 0.17 psu and 0.13 psu, respectively. It is important that caution should be exercised when using Aquarius salinity data in areas with high radio frequency interference (RFI) and heavy rainfall, close to the coast lines where leakage of land signals may significantly affect the quality of the SSS data, and at high-latitude oceans where the L-band radiometer has poor sensitivity to SSS.
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Status of Aquarius Salinity
2018 IEEE 15th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment (MicroRad), 2018Co-Authors: David Le Vine, Gary Lagerloef, Thomas Meissner, Emmanuel P. Dinnat, Liang Hong, Frank J. WentzAbstract:Aquarius, an L-band radar/radiometer instrument combination designed to measure ocean salinity. It was launched June 10, 2011 as part of the Aquarius/SAC-D observatory, a partnership between NASA, which provided Aquarius, and the Argentine space agency (CONAE) which provided the spacecraft bus, SAC-D. The observatory was lost four years later on June 7, 2015 when a failure in the power distribution network resulted in loss of control of the spacecraft. The Aquarius Mission formally ended December 31, 2017. The last major milestone was the release of the Project's final version of the salinity retrieval (Version 5.0). Version 5.0 meets the Mission requirements for accuracy and reflects the continuing progress and understanding developed by the Science Team over the lifetime of the mission.
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Verifying Aquarius Radiometer Calibration Drift Using in Situ Data
2018 IEEE 15th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment (MicroRad), 2018Co-Authors: Gary Lagerloef, David CareyAbstract:The Aquarius satellite mission was developed to measure the ocean's sea surface salinity (SSS) field and to investigate the links between changes in the global water cycle, ocean circulation and climate variability. The mission ended in June 2015 because of a power supply malfunction on the satellite. A recent data re-calibration and re-processing as produced Aquarius data version V5.0, released in December 2017. Key Aquarius science objectives were to (1) map the mean SSS field, (2) measure the annual SSS cycle, and (3) document interannual variations, within a three-year minimum duration. This study addresses objectives (2) and (3) by using co-located in situ data to verify that there is no significant spurious radiometer calibration drift on these time scales. The analysis converts the in situ salinity and temperature data (primarily from Argo floats) to an expected radiometer brightness temperature (TB), and computes the differences of these from the Aquarius radiometer-derived TB. The crux of the analysis is separating the sensor drift from the varying environmental corrections in the retrieval algorithm. The approach is to aggregate these co-located Tb differences within geographical zones (for example northern and southern hemispheres, ascending and descending passes), and then comparing the differences between these zones (double-difference). Next, regression analyses isolate the sensor variations from the environmental ones. The key assumption is that the long term (seasonal to interannual) radiometer calibration drift is a common signal among the various zones. This report explains this calculation and presents the results achieved with Aquarius V5.0 ocean salinity data release. Calibration histories for each of the six Aquarius radiometer channels are derived. The residuals are attributed to environmental model errors within each zone. Understanding these remains more problematic. The future study will be to adapt the technique to SMAP, and eventually SMOS measurements to enable a systematic cross-calibration of the different satellite systems and obtain a reliable combined multi-year time series for studying ocean trends.
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Recent improvements in L-band observations of ocean salinity by Aquarius
2016 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM), 2016Co-Authors: Emmanuel P. Dinnat, Gary Lagerloef, David Le Vine, Yan Soldo, Thomas MeissnerAbstract:Aquarius is an L-band system combining active and passive sensors and has observed the oceans, as well as land and the cryosphere, for almost 4 years. We present the latest improvements in the Aquarius algorithm for the retrieval of sea surface salinity.
D. Le M. Vine - One of the best experts on this subject based on the ideXlab platform.
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Radio Frequency Interference (RFI) Products on the Aquarius Website
IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018Co-Authors: P. De Matthaeis, D. Le M. Vine, Y. Soida, V. TsontosAbstract:Aquarius has produced maps of salinity by measuring Earth's natural emissions at L-band. However, measurements made by its instruments are affected by the presence of Radio Frequency Interference (RFI). For this reason, RFI detection algorithms had been implemented, both for the radiometer and the scatterometer, in order to reduce the impact of RFI on science data. In an effort to improve understanding of L-band RFI, the Aquarius mission has generated a new series of products. This contribution presents how these products were produced as well as the information that they contain. These products will be available starting at the end of January 2018 on the Aquarius website.
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Status of Aquarius and the salinity retrieval
2016 14th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment (MicroRad), 2016Co-Authors: D. Le M. Vine, E.p. Dinnat, F. Wentz, T. Miessner, G. LagerloefAbstract:Aquarius is a radiometer/scatterometer combination specifically designed for remote sensing of sea surface salinity. The instrument was launched on June 10, 2011 as part of the Aquarius/SAC-D observatory. The observatory and all instruments were lost on June 7, 2015 when a power failure on the satellite resulted in loss of control of the observatory. Mission operations have ended and the Aquarius science team is preparing a final reprocessing of the data. Among the improvements expected are correction for reflected radiation from the galaxy and an instrument-only correction for small “wiggles” in the calibration. Aquarius leaves a legacy of almost 4 years of data that are unique for accuracy and the combined active/passive look at the surface. This paper reports the status of mission and preliminary results of a new development in calibration.
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Aquarius status and recent results
Radio Science, 2014Co-Authors: D. Le M. Vine, P. De Matthaeis, S. Abraham, G.s.e Lagerloef, Emmanuel P. Dinnat, C. UtkuAbstract:Aquarius is a combination active/passive instrument at L band designed to map sea surface salinity globally from space. The radiometer (passive) is the primary instrument for retrieving salinity, and the scatterometer (active) provides information to correct for a major source of error, sea surface roughness (waves). In addition, the radiometer includes a number of special features designed to meet the goal for this challenging measurement, including measurement of the third Stokes parameter to help with the correction for Faraday rotation and rapid sampling to help with the mitigation of radio frequency interference. Aquarius was launched on 10 June 2011 aboard the Aquarius/SAC-D observatory and has been working well. The salinity retrieval continues to improve, and the special features suggest the potential for new applications of remote sensing from space at L band.
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Aquarius active passive rfi environment at l band
IEEE Geoscience and Remote Sensing Letters, 2014Co-Authors: D. Le M. Vine, P. De MatthaeisAbstract:Active/Passive instrument combinations (i.e., radiometer and radar) are being developed at L-band for remote sensing of sea surface salinity and soil moisture. Aquarius is already in orbit and SMAP is planned for launch in the Fall of 2014. Aquarius has provided for the first time a simultaneous look at the Radio Frequency Interference (RFI) environment from space for both active and passive instruments. The RFI environment for the radiometer observations is now reasonably well known and examples from Aquarius are presented in this manuscript that show that RFI is an important consideration for the scatterometer as well. In particular, extensive areas of the USA, Europe and Asia exhibit strong RFI in both the radiometer band at 1.41 GHz and in the band at 1.26 GHz employed by the Aquarius scatterometer. Furthermore, in areas such as the USA, where RFI at 1.4 GHz is relatively well controlled, RFI in the scatterometer band maybe the limiting consideration for the operation of combination active/passive instruments.
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Aquarius radiometer status
2014 13th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment (MicroRad), 2014Co-Authors: D. Le M. Vine, T Meissner, P. De Matthaeis, C. Utku, J.r. Piepmeier, E.p. Dinnat, S. Abraham, G.s.e Lagerloef, Frank J. WentzAbstract:Aquarius was launched on June 10, 2011 as part of the Aquarius/SAC-D observatory and the instrument has been operating continuously since being turned on in August of the same year. The initial map of sea surface salinity was released one month later (September) and the quality of the retrieval has continuously improved since then. The Aquarius radiometers include several special features such as measurement of the third Stokes parameter, fast sampling, and careful thermal control, and a combined passive/active instrument. Aquarius is working well and in addition to helping measure salinity, the radiometer special features are generating new results.
Guillermo E Parada - One of the best experts on this subject based on the ideXlab platform.
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the helicase Aquarius emb 4 is required to overcome intronic barriers to allow nuclear rnai pathways to heritably silence transcription
Developmental Cell, 2017Co-Authors: Alper Akay, Tomas Di Domenico, Kin Man Suen, Amena Nabih, Guillermo E ParadaAbstract:Small RNAs play a crucial role in genome defense against transposable elements and guide Argonaute proteins to nascent RNA transcripts to induce co-transcriptional gene silencing. However, the molecular basis of this process remains unknown. Here, we identify the conserved RNA helicase Aquarius/EMB-4 as a direct and essential link between small RNA pathways and the transcriptional machinery in Caenorhabditis elegans. Aquarius physically interacts with the germline Argonaute HRDE-1. Aquarius is required to initiate small-RNA-induced heritable gene silencing. HRDE-1 and Aquarius silence overlapping sets of genes and transposable elements. Surprisingly, removal of introns from a target gene abolishes the requirement for Aquarius, but not HRDE-1, for small RNA-dependent gene silencing. We conclude that Aquarius allows small RNA pathways to compete for access to nascent transcripts undergoing co-transcriptional splicing in order to detect and silence transposable elements. Thus, Aquarius and HRDE-1 act as gatekeepers coordinating gene expression and genome defense.
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the Aquarius emb 4 helicase licenses co transcriptional gene silencing
bioRxiv, 2016Co-Authors: Alper Akay, Tomas Di Domenico, Kin Man Suen, Amena Nabih, Guillermo E Parada, Mark Larance, Ragini Medhi, Ahmet C Berkyurek, Christopher J Wedeles, Xinlian ZhangAbstract:Small RNAs (sRNAs) play an ancient role in genome defence against transposable elements. In animals, plants and fungi small RNAs guide Argonaute proteins to nascent RNA transcripts to induce co-transcriptional gene silencing. In animals the link between small RNA pathways and the transcriptional machinery remains unclear. Here we show that the Caenorhabditis elegans germline Argonaute HRDE-1 physically interacts with the conserved RNA helicase Aquarius/EMB-4. We demonstrate that the Aquarius/EMB-4 helicase activity is required to initiate small RNA-induced co-transcriptional gene silencing. HRDE-1 and Aquarius/EMB-4 are required to silence the transcription of overlapping sets of transposable elements. Surprisingly, removal of introns from a small RNA pathway target abolishes the requirement for Aquarius/EMB-4, but not HRDE-1, for gene silencing. We conclude that the Aquarius/EMB-4 helicase activity allows HRDE-1/sRNA complexes to efficiently engage nascent RNA transcripts - in competition with the general RNA processing machinery. We postulate that Aquarius/EMB-4 facilitates the surveillance of the nascent transcriptome to detect and silence transposable elements through small RNA pathways.
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The Aquarius/EMB-4 helicase licenses co-transcriptional gene silencing
bioRxiv, 2016Co-Authors: Alper Akay, Tomas Di Domenico, Kin Man Suen, Amena Nabih, Guillermo E Parada, Mark Larance, Ragini Medhi, Ahmet C Berkyurek, Christopher J Wedeles, Xinlian ZhangAbstract:Small RNAs (sRNAs) play an ancient role in genome defence against transposable elements. In animals, plants and fungi small RNAs guide Argonaute proteins to nascent RNA transcripts to induce co-transcriptional gene silencing. In animals the link between small RNA pathways and the transcriptional machinery remains unclear. Here we show that the Caenorhabditis elegans germline Argonaute HRDE-1 physically interacts with the conserved RNA helicase Aquarius/EMB-4. We demonstrate that the Aquarius/EMB-4 helicase activity is required to initiate small RNA-induced co-transcriptional gene silencing. HRDE-1 and Aquarius/EMB-4 are required to silence the transcription of overlapping sets of transposable elements. Surprisingly, removal of introns from a small RNA pathway target abolishes the requirement for Aquarius/EMB-4, but not HRDE-1, for gene silencing. We conclude that the Aquarius/EMB-4 helicase activity allows HRDE-1/sRNA complexes to efficiently engage nascent RNA transcripts - in competition with the general RNA processing machinery. We postulate that Aquarius/EMB-4 facilitates the surveillance of the nascent transcriptome to detect and silence transposable elements through small RNA pathways.
