Histone H2A monoubiquitination is associated with transcriptional repression and needs to be removed by deubiquitinases to facilitate gene transcription in eukaryotes.However,the deubiquitinase responsible for genome-...Histone H2A monoubiquitination is associated with transcriptional repression and needs to be removed by deubiquitinases to facilitate gene transcription in eukaryotes.However,the deubiquitinase responsible for genome-wide H2A deubiquitination in plants has yet to be identified.In this study,we found that the previously identified PWWP-EPCR-ARID-TRB(PEAT)complex components interact with both the ubiquitin-specific protease UBP5 and the redundant histone acetyltransferases HAM1 and HAM2(HAM1/2)to form a larger version of PEAT complex in Arabidopsis thaliana.UBP5 functions as an H2A deubiquitinase in a nucleosome substrate-dependent manner in vitro and mediates H2A deubiquitination at the whole-genome level in vivo.HAM1/2 are shared subunits of the PEAT complex and the conserved NuA4 histone acetyltransferase com-plex,and are responsible for histone H4K5 acetylation.Within the PEAT complex,the PWWP components(PWWP1,PWWP2,and PWWP3)directly interact with UBP5 and are necessary for UBP5-mediated H2A deu-biquitination,while the EPCR components(EPCR1 and EPCR2)directly interact with HAM1/2 and are required for HAM1/2-mediated H4K5acetylation.Collectively,our study not onlyidentifies dual roles of thePEAT com-plex in H2A deubiquitination and H4K5 acetylation but also illustrates how these processes collaborate at the whole-genome level to regulate the transcription and development in plants.展开更多
“Ionic wind”generators are used as the main propulsion system in ion propulsion unmanned aerial vehicles(UAVs).Owing to the large size and poor stiffness of the electrode array in the propulsion system,the electrode...“Ionic wind”generators are used as the main propulsion system in ion propulsion unmanned aerial vehicles(UAVs).Owing to the large size and poor stiffness of the electrode array in the propulsion system,the electrode array is prone to deformation under the flight load.In this work,the thrust characteristics and static aeroelastic properties of“ionic wind”propulsion systems were analyzed in detail.The simulation model for an“ionic wind”propulsion system was established by coupling a two-dimensional gas discharge model with a gas dynamics model.The influences of electrode voltage,spacing,size,and shape on the performance of the propulsion system were investigated.The fluid-solid interaction method was used to solve static aeroelastic characteristics under deformation.The aerodynamic and thrust performances of the elastic state and the rigid state were compared.It was found that the operating voltage,the distance between two electrodes,and the emitter radius had greater impacts on the thrust of the propulsion system.The propulsion system had a small contribution to the lift but a large contribution to the drag.In the elastic state,the lift coefficient accounted for 12.2%,and the drag coefficient accounted for 25.8%.Under the action of the downwash airflow from the wing,the propulsion system formed an upward moment around the center of mass,which contributed greatly to the pitching moment derivative of the whole aircraft.In the elastic state,the pitching moment derivative accounted for 29.7%.After elastic deformation,the thrust action point moved upward by 28.7 mm.Hence,the no lift pitching moment is reduced by 0.104 N$m,and the pitching moment coefficient is reduced by 0.014,causing a great impact on the longitudinal trimming of the whole aircraft.展开更多
An insulator surface charge may be responsible for flashover along the insulator surface.In this study,experimental investigations of post insulator surface charge are performed using a variety of voltage,gas type,and...An insulator surface charge may be responsible for flashover along the insulator surface.In this study,experimental investigations of post insulator surface charge are performed using a variety of voltage,gas type,and gas pressure conditions.Combining the model of surface charge transport,the dominant charge transition is revealed considering gas partial discharge.The results show that hetero‐polar charge accumulates near the high voltage electrodes on the insulator at one atmospheric pressure with an applied DC voltage ranging from-10 to-60 kV.The area ratio of the hetero‐polar charge increases from 23%to 53%.It also generates a reversed polarity of surface charges.Under-20 kV,the surface charge near the grounded electrode gradually becomes homo‐polar charges with the decrease of SF6 in 0.5 MPa SF6/N2 gas mixtures.In this case,the most dominant pathway for charge accumulation is through the insulation gas rather than the insulator.For the 20%SF6/80%N2 gas mixtures,homo‐polar charge speckles appear near the grounded plate electrode when the pressure of SF6/N2 gas mixtures decreases to 0.1 MPa.This means that the partial discharge occurs in gas side under a lower gas pressure.Refer to the presenting findings,the dominant charge transition on post in-sulators is provided as an important reference.展开更多
目的:收集关于神经示踪技术应用于实验针灸研究的相关文献,总结分析其在腧穴、经脉、脏腑等方面的应用状况。方法:本研究以"示踪技术OR神经示踪技术OR示踪剂OR神经示踪剂OR示踪OR神经示踪"和"针灸OR针刺OR电针OR耳针OR眼...目的:收集关于神经示踪技术应用于实验针灸研究的相关文献,总结分析其在腧穴、经脉、脏腑等方面的应用状况。方法:本研究以"示踪技术OR神经示踪技术OR示踪剂OR神经示踪剂OR示踪OR神经示踪"和"针灸OR针刺OR电针OR耳针OR眼针OR经脉OR穴区OR腧穴OR穴位注射"为检索词检索中国知网(CNKI,1979-2017)、万方数据知识平台(Wan-Fang Data,1990-2017)、维普资讯中文期刊服务平台(VIP Date,1989-2017);以"neural tracing technique OR neuroanatomical tracing OR neuronal tracers"and"acupuncture OR electroacupuncture OR auricular acupuncture OR eye acupuncture OR meridians OR acupuncture points OR acupoint injection"为关键词检索英文数据库PubMed(1997-2017)。结果:共收录与本研究相关的文献94篇。其中使用最多的神经示踪剂是辣根过氧化物酶和霍乱毒素亚单位B,采用的实验动物有大鼠、家兔、猫和猴等,示踪剂的注射部位以腧穴居多。示踪剂注射后动物的存活时间从1 d到12周不等,所标记的神经成分包括感觉、运动和自主神经系统相关的神经元及其神经纤维。这些文献主要揭示了腧穴和脏腑的神经支配具有区域性和节段性特征,二者之间存在密切的神经解剖学联系,而其相关的神经元和神经纤维的化学特征(通过免疫荧光组织化学染色显示)与针灸作用途径密切相关。结论:应用神经示踪技术可以从神经通路/环路及其相关化学性质等不同角度更加深入地了解针灸的作用途径,这也为该项技术在将来的实验针灸研究中发挥更大的作用奠定了基础。展开更多
Although the mechanism of DNA methylationmediated gene silencing is extensively studied, relatively little is known about how promoter methylated genes are protected from transcriptional silencing. SUVH1, an Arabidops...Although the mechanism of DNA methylationmediated gene silencing is extensively studied, relatively little is known about how promoter methylated genes are protected from transcriptional silencing. SUVH1, an Arabidopsis Su(var)3-9 homolog, was previously shown to be required for the expression of a few promoter methylated genes. By chromatin immunoprecipitation combined with sequencing, we demonstrate that SUVH1 binds to methylated genomic loci targeted by RNA-directed DNA methylation. SUVH1 and its homolog SUVH3 function partially redundantly and interact with three DNAJ domain-containing homologs, SDJ1, SDJ2, and SDJ3, thus forming a complex which we named SUVH-SDJ. The SUVH-SDJ complex components are co-localized in a large number of methylated promoters and are required for the expression of a subset of promoter methylated genes. We demonstrate that the SUVHSDJ complex components have transcriptional activation activity. SUVH1 and SUVH3 function synergistically with SDJ1,SDJ2, and SDJ3 and are required for plant viability. This study reveals how the SUVH-SDJ complex protects promoter methylated genes from transcriptional silencing and suggests that the transcriptional activation of promoter methylated genes mediated by the SUVH-SDJ complex may play a critical role in plant growth and development.展开更多
Rapid developments in EHV/UHV transmission systems require a deeper understanding of the mechanism of long air gap discharge.Leader propagation is one of the main processes in long gap breakdown.In this paper,the lead...Rapid developments in EHV/UHV transmission systems require a deeper understanding of the mechanism of long air gap discharge.Leader propagation is one of the main processes in long gap breakdown.In this paper,the leader propagation characteristics of real size±800 kV UHVDC transmission tower gaps under positive switching impulse voltages(185/2290μs)are investigated.An integrated observation platform consisting of an impulse voltage divider,a coaxial shunt,a high-speed video camera,and a set of integrated optical electric field sensors(IOES),is established.The waveforms of impulse voltage,discharge current,electric field variation at specific positions,and time-resolved photographs of discharge morphology are recorded.Axial leader velocity and the relationship between leader advancements and injected charge are obtained.The typical value of leader stable propagation velocity is 1.7–2.2 cm/μs,which varies slightly with the gap length and applied voltage amplitude.The leader velocity in the re-illumination process is much higher,and is seen as varying from 5 cm/μs to 30 cm/μs,with an average value around 10 cm/μs.The charge in leader channel per unit length is 20–40μC/m,which illustrates a near-direct proportion relationship between discharge current and leader velocity.The observed parameters are important for further simulation of the tower gap breakdown processes.展开更多
LHP1 mediates recruitment of the PRC2 histone methyltransferase complex to chromatin and thereby facilitates maintenance of H3K27me3 on FLC, a key flowering repressor gene. Here, we report that the PWWP domain protei...LHP1 mediates recruitment of the PRC2 histone methyltransferase complex to chromatin and thereby facilitates maintenance of H3K27me3 on FLC, a key flowering repressor gene. Here, we report that the PWWP domain proteins （PDPs） interact with FVE and MSI5 to suppress FLC expression and thereby promote flowering. We demonstrated that FVE, MSI5, and PDP3 were co-purified with LHP1. The H3K27me3 level on FLC was decreased in the pdp mutants as welt as in the fve/ msi5 double mutant. This study suggests that PDPs function together with FVE and MSI5 to regulate the function of the PRC2 complex on FLC.展开更多
Trimethylated histone H3 lysine 27(H3 K27 me3)is a repressive histone marker that regulates a variety of developmental processes,including those that determine flowering time.However,relatively little is known about t...Trimethylated histone H3 lysine 27(H3 K27 me3)is a repressive histone marker that regulates a variety of developmental processes,including those that determine flowering time.However,relatively little is known about the mechanism of how H3 K27 me3 is recognized to regulate transcription.Here,we identified BAH domain-containing transcriptional regulator 1(BDT1)as an H3 K27 me3 reader.BDT1 is responsible for preventing flowering by suppressing the expression of flowering genes.Mutation of the H3 K27 me3 recognition sites in the BAH domain disrupted the binding of BDT1 to H3 K27 me3,leading to de-repression of H3 K27 me3-enriched flowering genes and an earlyflowering phenotype.We also found that BDT1 interacts with a family of PHD finger-containing proteins,which we named PHD1–6,and with CPL2,a Pol II carboxyl terminal domain(CTD)phosphatase responsible for transcriptional repression.Pull-down assays showed that the PHD finger-containing proteins can enhance the binding of BDT1 to the H3 K27 me3 peptide.Mutations in all of the PHD genes caused increased expression of flowering genes and an earlyflowering phenotype.This study suggests that the binding of BDT1 to the H3 K27 me3 peptide,which is enhanced by PHD proteins,is critical for preventing early flowering.展开更多
In eukaryotes,MEDIATOR is a conserved multisubunit complex that links transcription factors and RNA polymerase II and that thereby facilitates transcriptional initiation.Although the composition of MEDIATOR has been w...In eukaryotes,MEDIATOR is a conserved multisubunit complex that links transcription factors and RNA polymerase II and that thereby facilitates transcriptional initiation.Although the composition of MEDIATOR has been well studied in yeast and mammals,relatively little is known about the composition of MEDIATOR in plants.By affinity purification followed by mass spectrometry,we identified 28 conserved MEDIATOR subunits in Arabidopsis thaliana,including putative MEDIATOR subunits that were not previously validated.Our results indicated that MED34,MED35,MED36,and MED37 are not Arabidopsis MEDIATOR subunits,as previously proposed.Our results also revealed that two homologous CBP/p300 histone acetyltransferases,HAC1 and HAC5(HAC1/5)are in fact plant-specific MEDIATOR subunits.The MEDIATOR subunits MED8 and MED25(MED8/25)are partially responsible for the association of MEDIATOR with HAC1/5,MED8/25 and HAC1/5 co-regulate gene expression and thereby affect flowering time and floral development.Our in vitro observations indicated that MED8 and HAC1 form liquid-like droplets by phase separation,and our in vivo observations indicated that these droplets co-localize in the nuclear bodies at a subset of nuclei.The formation of liquid-like droplets is required for MED8 to interact with RNA polymerase II.In summary,we have identified all of the components of Arabidopsis MEDIATOR and revealed the mechanism underlying the link of histone acetylation and transcriptional regulation.展开更多
The SAGA(Spt-Ada-Gcn5 acetyltransferase)complex is an evolutionarily conserved histone acetyltransferase complex that has a critical role in histone acetylation,gene expression,and various developmental processes in e...The SAGA(Spt-Ada-Gcn5 acetyltransferase)complex is an evolutionarily conserved histone acetyltransferase complex that has a critical role in histone acetylation,gene expression,and various developmental processes in eukaryotes.However,little is known about the composition and function of the SAGA complex in plants.In this study,we found that the SAGA complex in Arabidopsis thaliana contains not only conserved subunits but also four plant-specific subunits:three functionally redundant paralogs,SCSI,SCS2A,and SCS2B(SCS1/2A/2B),and a TAF-like subunit,TAFL.Mutations in SCS1/2A/2B lead to defective phenotypes similar to those caused by mutations in the genes encoding conserved SAGA subunits HAG1 and ADA2B,including delayed juvenile-to-adult phase transition,late flowering,and increased trichome density.Furthermore,we demonstrated that SCS1/2A/2B are required for the function of the SAGA complex in histone acetylation,thereby promoting the transcription of development-related genes.These results together suggest that SCS1/2A/2B are core subunits of the SAGA complex in Arabidopsis.Compared with SAGA complexes in other eukaryotes,the SAGA complexes in plants have evolved unique features that are necessary for normal growth and development.展开更多
The SU(VAR)-3-9-related protein family member SUVR2 has been previously identified to be involved in transcriptional gene silencing both in RNA-dependent and-independent pathways. It interacts with the chromatin-remod...The SU(VAR)-3-9-related protein family member SUVR2 has been previously identified to be involved in transcriptional gene silencing both in RNA-dependent and-independent pathways. It interacts with the chromatin-remodeling proteins CHR19,CHR27, and CHR28(CHR19/27/28), which are also involved in transcriptional gene silencing. Here our study demonstrated that SUVR2 is almost fully mono-sumoylated in vivo. We successfully identified the exact SUVR2 sumoylation site by combining in vitro mass spectrometric analysis and in vivo immunoblotting confirmation. The luminescence imaging assay and quantitative RT-PCR results demonstrated that SUVR2 sumoylation is involved in transcriptional gene silencing. Furthermore, we found that SUVR2 sumoylation is required for the interaction of SUVR2 with CHR19/27/28, which is consistent with the fact that SUMO proteins are necessary for transcriptional gene silencing. These results suggest that SUVR2 sumoylation contributes to transcriptional gene silencing by facilitating the interaction of SUVR2 with the chromatin-remodeling proteins CHR19/27/28.展开更多
Although two Enhancer of Polycomb-like proteins,EPL1 A and EPL1 B(EPL1 A/B),are known to be conserved and characteristic subunits of the Nu A4-type histone acetyltransferase complex in Arabidopsis thaliana,the biologi...Although two Enhancer of Polycomb-like proteins,EPL1 A and EPL1 B(EPL1 A/B),are known to be conserved and characteristic subunits of the Nu A4-type histone acetyltransferase complex in Arabidopsis thaliana,the biological function of EPL1 A/B and the mechanism by which EPL1 A/B function in the complex remain unknown.Here,we report that EPL1 A/B are required for the histone acetyltransferase activity of the Nu A4 complex on the nucleosomal histone H4 in vitro and for the enrichment of histone H4 K5 acetylation at thousands of protein-coding genes in vivo.Our results suggest that EPL1 A/B are required for linking the Nu A4 catalytic subunits HISTONE ACETYLTRANSFERASE OF THE MYST FAMILY 1(HAM1)and HAM2 with accessory subunits in the Nu A4 complex.EPL1 A/B function redundantly in regulating plant development especially in chlorophyll biosynthesis and de-etiolation.The EPL1 A/B-dependent transcription and H4 K5 Ac are enriched at genes involved in chlorophyll biosynthesis and photosynthesis.We also find that EAF6,another characteristic subunit of the Nu A4 complex,contributes to de-etiolation.These results suggest that the Arabidopsis Nu A4 complex components function as a whole to mediate histone acetylation and transcriptional activation specifically at light-responsive genes and are critical for photomorphogenesis.展开更多
基金supported by the National Natural Science Foundation of China(grant number:32025003).
文摘Histone H2A monoubiquitination is associated with transcriptional repression and needs to be removed by deubiquitinases to facilitate gene transcription in eukaryotes.However,the deubiquitinase responsible for genome-wide H2A deubiquitination in plants has yet to be identified.In this study,we found that the previously identified PWWP-EPCR-ARID-TRB(PEAT)complex components interact with both the ubiquitin-specific protease UBP5 and the redundant histone acetyltransferases HAM1 and HAM2(HAM1/2)to form a larger version of PEAT complex in Arabidopsis thaliana.UBP5 functions as an H2A deubiquitinase in a nucleosome substrate-dependent manner in vitro and mediates H2A deubiquitination at the whole-genome level in vivo.HAM1/2 are shared subunits of the PEAT complex and the conserved NuA4 histone acetyltransferase com-plex,and are responsible for histone H4K5 acetylation.Within the PEAT complex,the PWWP components(PWWP1,PWWP2,and PWWP3)directly interact with UBP5 and are necessary for UBP5-mediated H2A deu-biquitination,while the EPCR components(EPCR1 and EPCR2)directly interact with HAM1/2 and are required for HAM1/2-mediated H4K5acetylation.Collectively,our study not onlyidentifies dual roles of thePEAT com-plex in H2A deubiquitination and H4K5 acetylation but also illustrates how these processes collaborate at the whole-genome level to regulate the transcription and development in plants.
文摘“Ionic wind”generators are used as the main propulsion system in ion propulsion unmanned aerial vehicles(UAVs).Owing to the large size and poor stiffness of the electrode array in the propulsion system,the electrode array is prone to deformation under the flight load.In this work,the thrust characteristics and static aeroelastic properties of“ionic wind”propulsion systems were analyzed in detail.The simulation model for an“ionic wind”propulsion system was established by coupling a two-dimensional gas discharge model with a gas dynamics model.The influences of electrode voltage,spacing,size,and shape on the performance of the propulsion system were investigated.The fluid-solid interaction method was used to solve static aeroelastic characteristics under deformation.The aerodynamic and thrust performances of the elastic state and the rigid state were compared.It was found that the operating voltage,the distance between two electrodes,and the emitter radius had greater impacts on the thrust of the propulsion system.The propulsion system had a small contribution to the lift but a large contribution to the drag.In the elastic state,the lift coefficient accounted for 12.2%,and the drag coefficient accounted for 25.8%.Under the action of the downwash airflow from the wing,the propulsion system formed an upward moment around the center of mass,which contributed greatly to the pitching moment derivative of the whole aircraft.In the elastic state,the pitching moment derivative accounted for 29.7%.After elastic deformation,the thrust action point moved upward by 28.7 mm.Hence,the no lift pitching moment is reduced by 0.104 N$m,and the pitching moment coefficient is reduced by 0.014,causing a great impact on the longitudinal trimming of the whole aircraft.
基金supported by the National Natural Science Foundation of China,Grant Numbers:52237007 and 51977063Natural Science Foundation of Hunan Province,Grant Number:2022JJ20010.
文摘An insulator surface charge may be responsible for flashover along the insulator surface.In this study,experimental investigations of post insulator surface charge are performed using a variety of voltage,gas type,and gas pressure conditions.Combining the model of surface charge transport,the dominant charge transition is revealed considering gas partial discharge.The results show that hetero‐polar charge accumulates near the high voltage electrodes on the insulator at one atmospheric pressure with an applied DC voltage ranging from-10 to-60 kV.The area ratio of the hetero‐polar charge increases from 23%to 53%.It also generates a reversed polarity of surface charges.Under-20 kV,the surface charge near the grounded electrode gradually becomes homo‐polar charges with the decrease of SF6 in 0.5 MPa SF6/N2 gas mixtures.In this case,the most dominant pathway for charge accumulation is through the insulation gas rather than the insulator.For the 20%SF6/80%N2 gas mixtures,homo‐polar charge speckles appear near the grounded plate electrode when the pressure of SF6/N2 gas mixtures decreases to 0.1 MPa.This means that the partial discharge occurs in gas side under a lower gas pressure.Refer to the presenting findings,the dominant charge transition on post in-sulators is provided as an important reference.
文摘目的:收集关于神经示踪技术应用于实验针灸研究的相关文献,总结分析其在腧穴、经脉、脏腑等方面的应用状况。方法:本研究以"示踪技术OR神经示踪技术OR示踪剂OR神经示踪剂OR示踪OR神经示踪"和"针灸OR针刺OR电针OR耳针OR眼针OR经脉OR穴区OR腧穴OR穴位注射"为检索词检索中国知网(CNKI,1979-2017)、万方数据知识平台(Wan-Fang Data,1990-2017)、维普资讯中文期刊服务平台(VIP Date,1989-2017);以"neural tracing technique OR neuroanatomical tracing OR neuronal tracers"and"acupuncture OR electroacupuncture OR auricular acupuncture OR eye acupuncture OR meridians OR acupuncture points OR acupoint injection"为关键词检索英文数据库PubMed(1997-2017)。结果:共收录与本研究相关的文献94篇。其中使用最多的神经示踪剂是辣根过氧化物酶和霍乱毒素亚单位B,采用的实验动物有大鼠、家兔、猫和猴等,示踪剂的注射部位以腧穴居多。示踪剂注射后动物的存活时间从1 d到12周不等,所标记的神经成分包括感觉、运动和自主神经系统相关的神经元及其神经纤维。这些文献主要揭示了腧穴和脏腑的神经支配具有区域性和节段性特征,二者之间存在密切的神经解剖学联系,而其相关的神经元和神经纤维的化学特征(通过免疫荧光组织化学染色显示)与针灸作用途径密切相关。结论:应用神经示踪技术可以从神经通路/环路及其相关化学性质等不同角度更加深入地了解针灸的作用途径,这也为该项技术在将来的实验针灸研究中发挥更大的作用奠定了基础。
基金supported by grants from National Key Research and Development Program of China (2016YFA0500801)
文摘Although the mechanism of DNA methylationmediated gene silencing is extensively studied, relatively little is known about how promoter methylated genes are protected from transcriptional silencing. SUVH1, an Arabidopsis Su(var)3-9 homolog, was previously shown to be required for the expression of a few promoter methylated genes. By chromatin immunoprecipitation combined with sequencing, we demonstrate that SUVH1 binds to methylated genomic loci targeted by RNA-directed DNA methylation. SUVH1 and its homolog SUVH3 function partially redundantly and interact with three DNAJ domain-containing homologs, SDJ1, SDJ2, and SDJ3, thus forming a complex which we named SUVH-SDJ. The SUVH-SDJ complex components are co-localized in a large number of methylated promoters and are required for the expression of a subset of promoter methylated genes. We demonstrate that the SUVHSDJ complex components have transcriptional activation activity. SUVH1 and SUVH3 function synergistically with SDJ1,SDJ2, and SDJ3 and are required for plant viability. This study reveals how the SUVH-SDJ complex protects promoter methylated genes from transcriptional silencing and suggests that the transcriptional activation of promoter methylated genes mediated by the SUVH-SDJ complex may play a critical role in plant growth and development.
基金supported by the National Natural Science Foundation of China under Grant 51325703,51377094Fund of the National Priority Basic Research of China(2011CB209403)。
文摘Rapid developments in EHV/UHV transmission systems require a deeper understanding of the mechanism of long air gap discharge.Leader propagation is one of the main processes in long gap breakdown.In this paper,the leader propagation characteristics of real size±800 kV UHVDC transmission tower gaps under positive switching impulse voltages(185/2290μs)are investigated.An integrated observation platform consisting of an impulse voltage divider,a coaxial shunt,a high-speed video camera,and a set of integrated optical electric field sensors(IOES),is established.The waveforms of impulse voltage,discharge current,electric field variation at specific positions,and time-resolved photographs of discharge morphology are recorded.Axial leader velocity and the relationship between leader advancements and injected charge are obtained.The typical value of leader stable propagation velocity is 1.7–2.2 cm/μs,which varies slightly with the gap length and applied voltage amplitude.The leader velocity in the re-illumination process is much higher,and is seen as varying from 5 cm/μs to 30 cm/μs,with an average value around 10 cm/μs.The charge in leader channel per unit length is 20–40μC/m,which illustrates a near-direct proportion relationship between discharge current and leader velocity.The observed parameters are important for further simulation of the tower gap breakdown processes.
基金supported by the National Key Research and Development Program of China (2016YFA0500801)the 973 Program (2011CB812600) from the Chinese Ministry of Science and Technology (to X.J.H.)the National Natural Science Foundation of China (31370317 and 31571584 to B.W.)
文摘LHP1 mediates recruitment of the PRC2 histone methyltransferase complex to chromatin and thereby facilitates maintenance of H3K27me3 on FLC, a key flowering repressor gene. Here, we report that the PWWP domain proteins （PDPs） interact with FVE and MSI5 to suppress FLC expression and thereby promote flowering. We demonstrated that FVE, MSI5, and PDP3 were co-purified with LHP1. The H3K27me3 level on FLC was decreased in the pdp mutants as welt as in the fve/ msi5 double mutant. This study suggests that PDPs function together with FVE and MSI5 to regulate the function of the PRC2 complex on FLC.
基金supported by the National Natural Science Foundation of China(32025003)by the National Key Research and Development Program of China(2016YFA0500801)from the Chinese Ministry of Science and Technology。
文摘Trimethylated histone H3 lysine 27(H3 K27 me3)is a repressive histone marker that regulates a variety of developmental processes,including those that determine flowering time.However,relatively little is known about the mechanism of how H3 K27 me3 is recognized to regulate transcription.Here,we identified BAH domain-containing transcriptional regulator 1(BDT1)as an H3 K27 me3 reader.BDT1 is responsible for preventing flowering by suppressing the expression of flowering genes.Mutation of the H3 K27 me3 recognition sites in the BAH domain disrupted the binding of BDT1 to H3 K27 me3,leading to de-repression of H3 K27 me3-enriched flowering genes and an earlyflowering phenotype.We also found that BDT1 interacts with a family of PHD finger-containing proteins,which we named PHD1–6,and with CPL2,a Pol II carboxyl terminal domain(CTD)phosphatase responsible for transcriptional repression.Pull-down assays showed that the PHD finger-containing proteins can enhance the binding of BDT1 to the H3 K27 me3 peptide.Mutations in all of the PHD genes caused increased expression of flowering genes and an earlyflowering phenotype.This study suggests that the binding of BDT1 to the H3 K27 me3 peptide,which is enhanced by PHD proteins,is critical for preventing early flowering.
基金supported by the National Natural Science Foundation of China(32025003)by the National Key Research and Development Program of China(2016YFA0500801)from the Chinese Ministry of Science and Technology。
文摘In eukaryotes,MEDIATOR is a conserved multisubunit complex that links transcription factors and RNA polymerase II and that thereby facilitates transcriptional initiation.Although the composition of MEDIATOR has been well studied in yeast and mammals,relatively little is known about the composition of MEDIATOR in plants.By affinity purification followed by mass spectrometry,we identified 28 conserved MEDIATOR subunits in Arabidopsis thaliana,including putative MEDIATOR subunits that were not previously validated.Our results indicated that MED34,MED35,MED36,and MED37 are not Arabidopsis MEDIATOR subunits,as previously proposed.Our results also revealed that two homologous CBP/p300 histone acetyltransferases,HAC1 and HAC5(HAC1/5)are in fact plant-specific MEDIATOR subunits.The MEDIATOR subunits MED8 and MED25(MED8/25)are partially responsible for the association of MEDIATOR with HAC1/5,MED8/25 and HAC1/5 co-regulate gene expression and thereby affect flowering time and floral development.Our in vitro observations indicated that MED8 and HAC1 form liquid-like droplets by phase separation,and our in vivo observations indicated that these droplets co-localize in the nuclear bodies at a subset of nuclei.The formation of liquid-like droplets is required for MED8 to interact with RNA polymerase II.In summary,we have identified all of the components of Arabidopsis MEDIATOR and revealed the mechanism underlying the link of histone acetylation and transcriptional regulation.
基金the National Natural Science Foundation of China(32025003)the National Key Research and Development Program of China(2016YFA0500801)from the Chinese Ministry of Science and Technology.
文摘The SAGA(Spt-Ada-Gcn5 acetyltransferase)complex is an evolutionarily conserved histone acetyltransferase complex that has a critical role in histone acetylation,gene expression,and various developmental processes in eukaryotes.However,little is known about the composition and function of the SAGA complex in plants.In this study,we found that the SAGA complex in Arabidopsis thaliana contains not only conserved subunits but also four plant-specific subunits:three functionally redundant paralogs,SCSI,SCS2A,and SCS2B(SCS1/2A/2B),and a TAF-like subunit,TAFL.Mutations in SCS1/2A/2B lead to defective phenotypes similar to those caused by mutations in the genes encoding conserved SAGA subunits HAG1 and ADA2B,including delayed juvenile-to-adult phase transition,late flowering,and increased trichome density.Furthermore,we demonstrated that SCS1/2A/2B are required for the function of the SAGA complex in histone acetylation,thereby promoting the transcription of development-related genes.These results together suggest that SCS1/2A/2B are core subunits of the SAGA complex in Arabidopsis.Compared with SAGA complexes in other eukaryotes,the SAGA complexes in plants have evolved unique features that are necessary for normal growth and development.
基金supported by the National Key Research and Development Program of China (2016YFA0500801 to Xinjian He)
文摘The SU(VAR)-3-9-related protein family member SUVR2 has been previously identified to be involved in transcriptional gene silencing both in RNA-dependent and-independent pathways. It interacts with the chromatin-remodeling proteins CHR19,CHR27, and CHR28(CHR19/27/28), which are also involved in transcriptional gene silencing. Here our study demonstrated that SUVR2 is almost fully mono-sumoylated in vivo. We successfully identified the exact SUVR2 sumoylation site by combining in vitro mass spectrometric analysis and in vivo immunoblotting confirmation. The luminescence imaging assay and quantitative RT-PCR results demonstrated that SUVR2 sumoylation is involved in transcriptional gene silencing. Furthermore, we found that SUVR2 sumoylation is required for the interaction of SUVR2 with CHR19/27/28, which is consistent with the fact that SUMO proteins are necessary for transcriptional gene silencing. These results suggest that SUVR2 sumoylation contributes to transcriptional gene silencing by facilitating the interaction of SUVR2 with the chromatin-remodeling proteins CHR19/27/28.
基金supported by the National Natural Science Foundation of China(32025003)the National Key Research and Development Program of China(2016YFA0500801)from the Chinese Ministry of Science and Technology。
文摘Although two Enhancer of Polycomb-like proteins,EPL1 A and EPL1 B(EPL1 A/B),are known to be conserved and characteristic subunits of the Nu A4-type histone acetyltransferase complex in Arabidopsis thaliana,the biological function of EPL1 A/B and the mechanism by which EPL1 A/B function in the complex remain unknown.Here,we report that EPL1 A/B are required for the histone acetyltransferase activity of the Nu A4 complex on the nucleosomal histone H4 in vitro and for the enrichment of histone H4 K5 acetylation at thousands of protein-coding genes in vivo.Our results suggest that EPL1 A/B are required for linking the Nu A4 catalytic subunits HISTONE ACETYLTRANSFERASE OF THE MYST FAMILY 1(HAM1)and HAM2 with accessory subunits in the Nu A4 complex.EPL1 A/B function redundantly in regulating plant development especially in chlorophyll biosynthesis and de-etiolation.The EPL1 A/B-dependent transcription and H4 K5 Ac are enriched at genes involved in chlorophyll biosynthesis and photosynthesis.We also find that EAF6,another characteristic subunit of the Nu A4 complex,contributes to de-etiolation.These results suggest that the Arabidopsis Nu A4 complex components function as a whole to mediate histone acetylation and transcriptional activation specifically at light-responsive genes and are critical for photomorphogenesis.
