The NAC(NAM,ATAF1/2,and CUC2)is a defense-associated transcription factor(TF)family that positively regulates defense responses to pathogen infection.TaNAC069 positively regulates resistance in wheat to Puccinia triti...The NAC(NAM,ATAF1/2,and CUC2)is a defense-associated transcription factor(TF)family that positively regulates defense responses to pathogen infection.TaNAC069 positively regulates resistance in wheat to Puccinia triticina(Pt).However,the molecular mechanism of its interaction with a Pt effector is not clear.We found that Pt effector Pt-1234 interacts with TaNAC069 to subvert host immunity during Pt infection.Quantitative real-time PCR analysis showed that expression of Pt-1234 was significantly upregulated during the early stage of Pt infection.Protein-mediated cell death assays in wheat showed that the Pt-1234 protein was unable to induce cell death in wheat near-isogenic lines carrying different leaf rust resistance genes,whereas it suppressed BAX-induced cell death in leaves of Nicotiana benthamiana.Silencing of Pt-1234 by host-induced gene silencing(HIGS)significantly reduced the virulence of Pt in the susceptible wheat variety Thatcher.The C subdomain of TaNAC069 was responsible for its interaction with Pt-1234,and the E subdomain was required for TaNAC069-mediated defense responses to Pt in planta.These findings indicate that Pt utilizes Pt-1234 to interact with wheat transcription factor TaNAC069 through its C subdomain,thereby modulating wheat immunity.展开更多
An accurate assessment of host and pathogen gene expression during infection is critical for understanding the molecular aspects of host-pathogen interactions.Often,pathogen-derived transcripts are difficult to ascert...An accurate assessment of host and pathogen gene expression during infection is critical for understanding the molecular aspects of host-pathogen interactions.Often,pathogen-derived transcripts are difficult to ascertain at early infection stages owing to the unfavourable transcript representation compared to the host genes.In this study,we compare two sequencing techniques,RNAseq and enrichment sequencing(RenSeq and PenSeq)of cDNA,to investigate gene expression patterns in the doubled monoploid potato(DM)infected with the late blight pathogen Phytophthora infestans.Our results reveal distinct advantages of cDNA RenSeq and PenSeq over traditional RNAseq in terms of target gene representation and transcriptional quantification at early infection stages.Throughout the infection time course,cDNA enrichment sequencing enables transcriptomic analyses for more targeted host and pathogen genes.For highly expressed genes that were sampled in parallel by both cDNA enrichment and RNAseq,a high level of concordance in expression profiles is observed,indicative of at least semi-quantitative gene expression representation following enrichment.展开更多
Rice blast disease caused by Magnaporthe oryzae poses a serious threat to rice security worldwide.This filamentous pathogen modulates rice defense responses by secreting effectors to facilitate infection.The phytohorm...Rice blast disease caused by Magnaporthe oryzae poses a serious threat to rice security worldwide.This filamentous pathogen modulates rice defense responses by secreting effectors to facilitate infection.The phytohormone jasmonic acid(JA)plays crucial roles in the response to rice blast fungus.However,how M.oryzae disrupts JA-mediated resistance in rice is not well understood.In this study,we identify a new effector,a chloroplast-targeting protein(MoCHT1),from M.oryzae.Knocking out MoCHT1 decreases virulence,whereas heterologous expression of MoCHT1 in rice compromises disease resistance.MoCHT1 interacts with a rice LESION AND LAMINA BENDING(OsLLB)protein,a negative regulator of JA biosynthesis in the chloroplast.Loss-of-function of Os LLB leads to increased JA accumulation,thereby improving resistance to rice blast.The interaction between MoCHT1 and OsLLB results in the inhibition of OsLLB degradation,consequently reducing JA accumulation,thereby impairing JA content and decreasing plant disease resistance.Overall,this study reveals the molecular mechanism by which M.oryzae utilizes MoCHT1 to subvert rice JA signaling,broadening our understanding of how pathogens circumvent host immune responses by manipulating plant defense hormone biosynthesis.展开更多
LysM proteins contain the lysin domain(LysM),bind chitin and are found in various organisms including fungi.In phytopathogenic fungi,certain LysM proteins act as effectors to inhibit host immunity,thus increasing fung...LysM proteins contain the lysin domain(LysM),bind chitin and are found in various organisms including fungi.In phytopathogenic fungi,certain LysM proteins act as effectors to inhibit host immunity,thus increasing fungal virulence.However,our understanding of the LysM protein family in Setosphaeria turcica is limited.In this study,eight StLysM genes are identified and designated as StLysM1 to StLysM8.The analysis of sequence features indicates that five proteins(StLysM1,StLysM2,StLysM5,StLysM6,and StLysM7)are potential effectors.Phylogenetic analysis suggests that the StLysMs are divided into fungal/bacterial and fungus-specific subclasses.Domain architecture analysis reveals that the five StLysM effectors exclusively harbor the LysM domain,whereas the other three StLysM proteins contain additional functional domains.Sequence conservation analysis shows that the fungal-specific LysM domain sequences share the ^(8)GDxTC^(12) and ^(29)WNP^(31) motifs as well as three highly conserved cysteine residues.Conversely,the LysM domain sequences from the bacterial/fungal branch have few conserved sites.Moreover,expression profiling analysis shows that the StLysM1 gene is significantly upregulated during the infection of maize.Yeast secretion assays and transient expression experiments demonstrate that StLysM1 is a secreted protein that can suppress BAX/INF1-induced programmed cell death in Nicotiana benthamiana.Further functional analysis suggests that St Lys M1 cannot interact with itself but it can bind chitin.The transient expression of StLysM1 inhibits the chitin-triggered plant immune response,increasing susceptibility to the phytopathogenic fungus Botrytis cinerea in N.benthamiana.This study reveals that the S.turcica LySM protein family consists of eight members,highlighting the significance of StLysM1 as a vital effector in regulating plant immunity.The results provide insight into StLysMs and establish a foundation for understanding the roles of StLysM proteins in the pathogenic process of S.turcica.展开更多
Inorganic phosphate(Pi)homeostasis in plants is regulated by inositol pyrophosphates(PP-InsPs),which mediate phosphate starvation responses.While beneficial microorganisms,such as arbuscular mycorrhizal fungi,contribu...Inorganic phosphate(Pi)homeostasis in plants is regulated by inositol pyrophosphates(PP-InsPs),which mediate phosphate starvation responses.While beneficial microorganisms,such as arbuscular mycorrhizal fungi,contribute to phosphate uptake,pathogenic fungi often exploit phosphate metabolism to enhance virulence.However,the exact mechanisms by which pathogens manipulate plant phosphate signaling remain largely unknown.Here,we highlight a recent study by Ulrich Schaffrath and colleagues(Science,2025)revealing that plant pathogenic fungi deploy conserved Nudix hydrolase effectors to hydrolyze PP-InsPs,thereby mimicking phosphate starvation and suppressing host immunity.These findings not only expand our understanding of plantpathogen interactions,but also open new avenues for crop protection and resistance breeding.展开更多
The sugar beet cyst nematode(Heterodera schachtii) is one of the most destructive pathogens in sugar beet production, which causes serious economic losses every year. Few molecular details of effectors of H. schachtii...The sugar beet cyst nematode(Heterodera schachtii) is one of the most destructive pathogens in sugar beet production, which causes serious economic losses every year. Few molecular details of effectors of H. schachtii parasitism are known. We analyzed the genome and transcriptome data of H. schachtii and identified multiple potential predicted proteins. After filtering out predicted proteins with high homology to other plant-parasitic nematodes, we performed functional validation of the remaining effector proteins. 37 putative effectors of H. schachtii were screened based on the Nicotiana benthamiana system for identifying the effectors that inhibit plant immune response, eventually determines 13 candidate effectors could inhibit cell death caused by Bax. Among the 13 effectors, nine have the ability to inhibit GPA2/RBP1-induced cell death. All 13 effectortriggered immunity(ETI) suppressor genes were analyzed by qRT-PCR and confirmed to result in a significant downregulation of one or more defense genes during infection compared to empty vector. For in situ hybridization,13 effectors were specifically expressed and located in esophageal gland cells. These data and functional analysis set the stage for further studies on the interaction of H. schachtii with host and H. schachtii parasitic control.展开更多
Plants deploy a two-layered immune system:pathogen-associated molecular pattern(PAMP)-triggered immunity(PTl)and effector-triggered immunity(ETI).While PTI is initiated by cell surface receptors,ETI relies on intracel...Plants deploy a two-layered immune system:pathogen-associated molecular pattern(PAMP)-triggered immunity(PTl)and effector-triggered immunity(ETI).While PTI is initiated by cell surface receptors,ETI relies on intracellular NLR receptors that recognize pathogen effectors(Jones et al.,2024).The nucleoporin CONSTITUTIVE EXPRESSER OF PATHOGENESIS-RELATED GENES 5(CPR5)is a key negative regulator of ETI.CPR5 integrates nuclear transport,cell cycle control,and RNA processing to suppress immune signaling(Wang et al.,2014;Gu et al.,2016;Peng et al.,2022).Recent work revealed that CPR5 also modulates immunity through another nucleoporin,GUANYLATE-BINDING PROTEIN-LIKE 3(GBPL3),which interaCtS with PWWP-DOMAIN INTERACTOR OF POLYCOMBS1(PWO1),a key component of the chromatin-associated methyltransferase POLYCOMB REPRESSIVE COMPLEX 2(PRC2)(Reimann et al.,2023;Pan et al.,2025).These findings suggest unexplored roles for chromatin remodeling in the CPR5-mediated immunity.展开更多
To fulfill the demands for higher quality,efficiency and flexibility in aviation industry,a multi-functional end effector is designed to automate the drilling and riveting processes in assembling carbon fiber reinforc...To fulfill the demands for higher quality,efficiency and flexibility in aviation industry,a multi-functional end effector is designed to automate the drilling and riveting processes in assembling carbon fiber reinforced polymer(CFRP)and aluminum components for a robotic aircraft assembly system.To meet the specific functional requirements for blind rivet installation on CFRP and aluminum materials,additional modules are incorporated on the end effector aside of the basic processing modules for drilling.And all of these processing modules allow for a onestep-drilling-countersinking process,hole inspection,automatic rivet feed,rivet geometry check,sealant application,rivet insertion and installation.Besides,to guarantee the better quality of the hole drilled and joints riveted,several online detection and adjustment measures are applied to this end effector,including the reference detection and perpendicular calibration,which could effectively ensure the positioning precision and perpendicular accuracy as demanded.Finally,the test result shows that this end effector is capable of producing each hole to a positioning precision within ±0.5 mm,aperpendicular accuracy within 0.3°,a diameter tolerance of H8,and a countersink depth tolerance of±0.01 mm.Moreover,it could drill and rivet up to three joints per minute,with acceptable shearing and tensile strength.展开更多
The innate immune system is the first line of defense against invading pathogens. Innate immune cells recognize molecular patterns from the pathogen and mount a response to resolve the infection. The production of pro...The innate immune system is the first line of defense against invading pathogens. Innate immune cells recognize molecular patterns from the pathogen and mount a response to resolve the infection. The production of proinflammatory cytokines and reactive oxygen species, phagocytosis, and induced programmed cell death are processes initiated by innate immune cells in order to combat invading pathogens. However, pathogens have evolved various virulence mechanisms to subvert these responses. One strategy utilized by Gram-negative bacterial pathogens is the deployment of a complex machine termed the type Ⅲ secretion system(T3SS). The T3SS is composed of a syringe-like needle structure and the effector proteins that are injected directly into a target host cell to disrupt a cellular response. The three human pathogenic Yersinia spp.(Y. pestis, Y. enterocolitica, and Y. pseudotuberculosis) are Gramnegative bacteria that share in common a 70 kb virulence plasmid which encodes the T3 SS. Translocation of the Yersinia effector proteins(YopE, YopH, YopT, YopM, YpkA/YopO, and YopP/J) into the target host cell results in disruption of the actin cytoskeleton to inhibit phagocytosis, downregulation of proinflammatory cytokine/chemokine production, and induction of cellular apoptosis of the target cell. Over the past 25 years, studies on the Yersinia effector proteins have unveiled tremendous knowledge of how the effectors enhance Yersinia virulence. Recently, the long awaited crystal structure of YpkA has been solved providing further insights into the activation of the YpkA kinase domain. Multisite autophosphorylation by YpkA to activate its kinase domain was also shown and postulated to serve as a mechanism to bypass regulation by host phosphatases. In addition, novel Yersinia effector protein targets, such as caspase-1, and signaling pathways including activation of the inflammasome were identified. In this review, we summarize the recent discoveries made on Yersinia effector proteins and their contribution to Yersinia pathogenesis.展开更多
The end-effector of the large space manipulator is employed to assist the manipulator in handling and manipulating large payloads on orbit.Currently,there are few researches about the end-effector,and the existing end...The end-effector of the large space manipulator is employed to assist the manipulator in handling and manipulating large payloads on orbit.Currently,there are few researches about the end-effector,and the existing end-effectors have some disadvantages,such as poor misalignment tolerance capability and complex mechanical components.According to the end positioning errors and the residual vibration characters of the large space manipulators,two basic performance requirements of the end-effector which include the capabilities of misalignment tolerance and soft capture are proposed.And the end-effector should accommodate the following misalignments of the mechanical interface.The translation misalignments in axial and radial directions and the angular misalignments in roll,pitch and yaw are ±100 mm,100 mm,±10°,±15°,±15°,respectively.Seven end-effector schemes are presented and the capabilities of misalignment tolerance and soft capture are analyzed elementarily.The three fingers-three petals end-effector and the steel cable-snared end-effector are the most feasible schemes among the seven schemes,and they are designed in detail.The capabilities of misalignment tolerance and soft capture are validated and evaluated,through the experiment on the micro-gravity simulating device and the dynamic analysis in ADAMS software.The results show that the misalignment tolerance capabilities of these two schemes could satisfy the requirement.And the translation misalignment tolerances in axial and radial directions and the angular misalignment tolerances in roll,pitch and yaw of the steel cable-snared end-effector are 30mm,15mm,6°,3° and 3° larger than those of the three fingers-three petals end-effector,respectively.And the contact force of the steel cable-snared end-effector is smaller and smoother than that of the three fingers-three petals end-effector.The end-effector schemes and research methods are beneficial to the developments of the large space manipulator end-effctor and the space docking mechanism.展开更多
基金funded by State Key Laboratory of North China Crop Improvement and Regulation(NCCIR2023ZZ-10)the National Natural Science Foundation of China(32172384 and 31501623)+1 种基金the Natural Science Foundation of Hebei(C2020204028)the Science and Technology Research Project of Higher Education of Hebei(ZC2023178).
文摘The NAC(NAM,ATAF1/2,and CUC2)is a defense-associated transcription factor(TF)family that positively regulates defense responses to pathogen infection.TaNAC069 positively regulates resistance in wheat to Puccinia triticina(Pt).However,the molecular mechanism of its interaction with a Pt effector is not clear.We found that Pt effector Pt-1234 interacts with TaNAC069 to subvert host immunity during Pt infection.Quantitative real-time PCR analysis showed that expression of Pt-1234 was significantly upregulated during the early stage of Pt infection.Protein-mediated cell death assays in wheat showed that the Pt-1234 protein was unable to induce cell death in wheat near-isogenic lines carrying different leaf rust resistance genes,whereas it suppressed BAX-induced cell death in leaves of Nicotiana benthamiana.Silencing of Pt-1234 by host-induced gene silencing(HIGS)significantly reduced the virulence of Pt in the susceptible wheat variety Thatcher.The C subdomain of TaNAC069 was responsible for its interaction with Pt-1234,and the E subdomain was required for TaNAC069-mediated defense responses to Pt in planta.These findings indicate that Pt utilizes Pt-1234 to interact with wheat transcription factor TaNAC069 through its C subdomain,thereby modulating wheat immunity.
基金supported by the Rural & Environment Science & Analytical Services (RESAS) Division of the Scottish Government through project JHI-B1-1the Biotechnology and Biological Sciences Research Council (BBSRC) through awards BB/ S015663/1+2 种基金BB/X009068/1Research Leaders 2025 fellowship funded by European Union’s Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement no. 754380the Research/Scientific Computing teams at The James Hutton Institute and NIAB for providing computational resources and technical support for the “UK’s Crop Diversity Bioinformatics HPC” (BBSRC grant BB/ S019669/1)。
文摘An accurate assessment of host and pathogen gene expression during infection is critical for understanding the molecular aspects of host-pathogen interactions.Often,pathogen-derived transcripts are difficult to ascertain at early infection stages owing to the unfavourable transcript representation compared to the host genes.In this study,we compare two sequencing techniques,RNAseq and enrichment sequencing(RenSeq and PenSeq)of cDNA,to investigate gene expression patterns in the doubled monoploid potato(DM)infected with the late blight pathogen Phytophthora infestans.Our results reveal distinct advantages of cDNA RenSeq and PenSeq over traditional RNAseq in terms of target gene representation and transcriptional quantification at early infection stages.Throughout the infection time course,cDNA enrichment sequencing enables transcriptomic analyses for more targeted host and pathogen genes.For highly expressed genes that were sampled in parallel by both cDNA enrichment and RNAseq,a high level of concordance in expression profiles is observed,indicative of at least semi-quantitative gene expression representation following enrichment.
基金funded by the Biological Breeding-National Science and Technology Major Projects(2023ZD04070)the National Natural Science Foundation of China(31970284,31900385)+1 种基金the Fujian Provincial Science and Technology Key Project(2022NZ030014)the Natural Science Foundation of Fujian Province,China(2023J01483,2022J01616)。
文摘Rice blast disease caused by Magnaporthe oryzae poses a serious threat to rice security worldwide.This filamentous pathogen modulates rice defense responses by secreting effectors to facilitate infection.The phytohormone jasmonic acid(JA)plays crucial roles in the response to rice blast fungus.However,how M.oryzae disrupts JA-mediated resistance in rice is not well understood.In this study,we identify a new effector,a chloroplast-targeting protein(MoCHT1),from M.oryzae.Knocking out MoCHT1 decreases virulence,whereas heterologous expression of MoCHT1 in rice compromises disease resistance.MoCHT1 interacts with a rice LESION AND LAMINA BENDING(OsLLB)protein,a negative regulator of JA biosynthesis in the chloroplast.Loss-of-function of Os LLB leads to increased JA accumulation,thereby improving resistance to rice blast.The interaction between MoCHT1 and OsLLB results in the inhibition of OsLLB degradation,consequently reducing JA accumulation,thereby impairing JA content and decreasing plant disease resistance.Overall,this study reveals the molecular mechanism by which M.oryzae utilizes MoCHT1 to subvert rice JA signaling,broadening our understanding of how pathogens circumvent host immune responses by manipulating plant defense hormone biosynthesis.
基金supported by the S&T Program of Hebei,China(23567601H)the Hebei Provincial Central Leading Local Science and Technology Development Fund Project,China(236Z6508G)+1 种基金the Basic Research Funds for Provincial Universities in Hebei Province,China(KY2022037 and KY2021042)the Natural Science Foundation of Hebei Province,China(C2023204100 and C2021204136)。
文摘LysM proteins contain the lysin domain(LysM),bind chitin and are found in various organisms including fungi.In phytopathogenic fungi,certain LysM proteins act as effectors to inhibit host immunity,thus increasing fungal virulence.However,our understanding of the LysM protein family in Setosphaeria turcica is limited.In this study,eight StLysM genes are identified and designated as StLysM1 to StLysM8.The analysis of sequence features indicates that five proteins(StLysM1,StLysM2,StLysM5,StLysM6,and StLysM7)are potential effectors.Phylogenetic analysis suggests that the StLysMs are divided into fungal/bacterial and fungus-specific subclasses.Domain architecture analysis reveals that the five StLysM effectors exclusively harbor the LysM domain,whereas the other three StLysM proteins contain additional functional domains.Sequence conservation analysis shows that the fungal-specific LysM domain sequences share the ^(8)GDxTC^(12) and ^(29)WNP^(31) motifs as well as three highly conserved cysteine residues.Conversely,the LysM domain sequences from the bacterial/fungal branch have few conserved sites.Moreover,expression profiling analysis shows that the StLysM1 gene is significantly upregulated during the infection of maize.Yeast secretion assays and transient expression experiments demonstrate that StLysM1 is a secreted protein that can suppress BAX/INF1-induced programmed cell death in Nicotiana benthamiana.Further functional analysis suggests that St Lys M1 cannot interact with itself but it can bind chitin.The transient expression of StLysM1 inhibits the chitin-triggered plant immune response,increasing susceptibility to the phytopathogenic fungus Botrytis cinerea in N.benthamiana.This study reveals that the S.turcica LySM protein family consists of eight members,highlighting the significance of StLysM1 as a vital effector in regulating plant immunity.The results provide insight into StLysMs and establish a foundation for understanding the roles of StLysM proteins in the pathogenic process of S.turcica.
基金the financial support from China Youth Science Foundation(22207037).
文摘Inorganic phosphate(Pi)homeostasis in plants is regulated by inositol pyrophosphates(PP-InsPs),which mediate phosphate starvation responses.While beneficial microorganisms,such as arbuscular mycorrhizal fungi,contribute to phosphate uptake,pathogenic fungi often exploit phosphate metabolism to enhance virulence.However,the exact mechanisms by which pathogens manipulate plant phosphate signaling remain largely unknown.Here,we highlight a recent study by Ulrich Schaffrath and colleagues(Science,2025)revealing that plant pathogenic fungi deploy conserved Nudix hydrolase effectors to hydrolyze PP-InsPs,thereby mimicking phosphate starvation and suppressing host immunity.These findings not only expand our understanding of plantpathogen interactions,but also open new avenues for crop protection and resistance breeding.
基金supported by the Open Fund of the Key Laboratory of Integrated Pest Management on Crop in Northwestern Oasis,Ministry of Agriculture and Rural Affairsof China(KFJJ202101)the National KeyR&D Program of China(2021YFD1400100)+1 种基金the National Natural Science Foundation of China(31972247)the Tianchi Talent Introduction Program in Xinjiang Uygur Autonomous Region,China and the Science and Technology Innovation Project of the Chinese Academy of Agricultural Sciences.
文摘The sugar beet cyst nematode(Heterodera schachtii) is one of the most destructive pathogens in sugar beet production, which causes serious economic losses every year. Few molecular details of effectors of H. schachtii parasitism are known. We analyzed the genome and transcriptome data of H. schachtii and identified multiple potential predicted proteins. After filtering out predicted proteins with high homology to other plant-parasitic nematodes, we performed functional validation of the remaining effector proteins. 37 putative effectors of H. schachtii were screened based on the Nicotiana benthamiana system for identifying the effectors that inhibit plant immune response, eventually determines 13 candidate effectors could inhibit cell death caused by Bax. Among the 13 effectors, nine have the ability to inhibit GPA2/RBP1-induced cell death. All 13 effectortriggered immunity(ETI) suppressor genes were analyzed by qRT-PCR and confirmed to result in a significant downregulation of one or more defense genes during infection compared to empty vector. For in situ hybridization,13 effectors were specifically expressed and located in esophageal gland cells. These data and functional analysis set the stage for further studies on the interaction of H. schachtii with host and H. schachtii parasitic control.
基金supported by grants from the National Natural Science Foundation of China(32270290)the Shanghai Engineering Research Center of Plant Germplasm Resources(17DZ2252700).
文摘Plants deploy a two-layered immune system:pathogen-associated molecular pattern(PAMP)-triggered immunity(PTl)and effector-triggered immunity(ETI).While PTI is initiated by cell surface receptors,ETI relies on intracellular NLR receptors that recognize pathogen effectors(Jones et al.,2024).The nucleoporin CONSTITUTIVE EXPRESSER OF PATHOGENESIS-RELATED GENES 5(CPR5)is a key negative regulator of ETI.CPR5 integrates nuclear transport,cell cycle control,and RNA processing to suppress immune signaling(Wang et al.,2014;Gu et al.,2016;Peng et al.,2022).Recent work revealed that CPR5 also modulates immunity through another nucleoporin,GUANYLATE-BINDING PROTEIN-LIKE 3(GBPL3),which interaCtS with PWWP-DOMAIN INTERACTOR OF POLYCOMBS1(PWO1),a key component of the chromatin-associated methyltransferase POLYCOMB REPRESSIVE COMPLEX 2(PRC2)(Reimann et al.,2023;Pan et al.,2025).These findings suggest unexplored roles for chromatin remodeling in the CPR5-mediated immunity.
基金supported by the National Natural Science Foundations of China(Nos.5157051626,51475225)
文摘To fulfill the demands for higher quality,efficiency and flexibility in aviation industry,a multi-functional end effector is designed to automate the drilling and riveting processes in assembling carbon fiber reinforced polymer(CFRP)and aluminum components for a robotic aircraft assembly system.To meet the specific functional requirements for blind rivet installation on CFRP and aluminum materials,additional modules are incorporated on the end effector aside of the basic processing modules for drilling.And all of these processing modules allow for a onestep-drilling-countersinking process,hole inspection,automatic rivet feed,rivet geometry check,sealant application,rivet insertion and installation.Besides,to guarantee the better quality of the hole drilled and joints riveted,several online detection and adjustment measures are applied to this end effector,including the reference detection and perpendicular calibration,which could effectively ensure the positioning precision and perpendicular accuracy as demanded.Finally,the test result shows that this end effector is capable of producing each hole to a positioning precision within ±0.5 mm,aperpendicular accuracy within 0.3°,a diameter tolerance of H8,and a countersink depth tolerance of±0.01 mm.Moreover,it could drill and rivet up to three joints per minute,with acceptable shearing and tensile strength.
基金Supported by the ASM Robert D Watkins Graduate FellowshipUC Davis Hellman Fellowship
文摘The innate immune system is the first line of defense against invading pathogens. Innate immune cells recognize molecular patterns from the pathogen and mount a response to resolve the infection. The production of proinflammatory cytokines and reactive oxygen species, phagocytosis, and induced programmed cell death are processes initiated by innate immune cells in order to combat invading pathogens. However, pathogens have evolved various virulence mechanisms to subvert these responses. One strategy utilized by Gram-negative bacterial pathogens is the deployment of a complex machine termed the type Ⅲ secretion system(T3SS). The T3SS is composed of a syringe-like needle structure and the effector proteins that are injected directly into a target host cell to disrupt a cellular response. The three human pathogenic Yersinia spp.(Y. pestis, Y. enterocolitica, and Y. pseudotuberculosis) are Gramnegative bacteria that share in common a 70 kb virulence plasmid which encodes the T3 SS. Translocation of the Yersinia effector proteins(YopE, YopH, YopT, YopM, YpkA/YopO, and YopP/J) into the target host cell results in disruption of the actin cytoskeleton to inhibit phagocytosis, downregulation of proinflammatory cytokine/chemokine production, and induction of cellular apoptosis of the target cell. Over the past 25 years, studies on the Yersinia effector proteins have unveiled tremendous knowledge of how the effectors enhance Yersinia virulence. Recently, the long awaited crystal structure of YpkA has been solved providing further insights into the activation of the YpkA kinase domain. Multisite autophosphorylation by YpkA to activate its kinase domain was also shown and postulated to serve as a mechanism to bypass regulation by host phosphatases. In addition, novel Yersinia effector protein targets, such as caspase-1, and signaling pathways including activation of the inflammasome were identified. In this review, we summarize the recent discoveries made on Yersinia effector proteins and their contribution to Yersinia pathogenesis.
基金supported by National Hi-tech Research and Development Program of China(863 Program,Grant No. 2006AA04Z228)
文摘The end-effector of the large space manipulator is employed to assist the manipulator in handling and manipulating large payloads on orbit.Currently,there are few researches about the end-effector,and the existing end-effectors have some disadvantages,such as poor misalignment tolerance capability and complex mechanical components.According to the end positioning errors and the residual vibration characters of the large space manipulators,two basic performance requirements of the end-effector which include the capabilities of misalignment tolerance and soft capture are proposed.And the end-effector should accommodate the following misalignments of the mechanical interface.The translation misalignments in axial and radial directions and the angular misalignments in roll,pitch and yaw are ±100 mm,100 mm,±10°,±15°,±15°,respectively.Seven end-effector schemes are presented and the capabilities of misalignment tolerance and soft capture are analyzed elementarily.The three fingers-three petals end-effector and the steel cable-snared end-effector are the most feasible schemes among the seven schemes,and they are designed in detail.The capabilities of misalignment tolerance and soft capture are validated and evaluated,through the experiment on the micro-gravity simulating device and the dynamic analysis in ADAMS software.The results show that the misalignment tolerance capabilities of these two schemes could satisfy the requirement.And the translation misalignment tolerances in axial and radial directions and the angular misalignment tolerances in roll,pitch and yaw of the steel cable-snared end-effector are 30mm,15mm,6°,3° and 3° larger than those of the three fingers-three petals end-effector,respectively.And the contact force of the steel cable-snared end-effector is smaller and smoother than that of the three fingers-three petals end-effector.The end-effector schemes and research methods are beneficial to the developments of the large space manipulator end-effctor and the space docking mechanism.
