Nonhost resistance is a phenomenon that enables plants to protect themselves against the majority of potential pathogens, and thus has a great potential for application in plant protection. We recently found that CfHN...Nonhost resistance is a phenomenon that enables plants to protect themselves against the majority of potential pathogens, and thus has a great potential for application in plant protection. We recently found that CfHNNI1 （for Cladosporium fulvum host and nonhost plant necrosis inducer 1） is an inducer of plant hypersensitive response （HR） and nonhost resistance. In this study, its functional mechanism was analyzed. CfHNN11 was a single copy gene in C. fulvum genome. The functional ORF of the CfHNN11 cDNA was ATG3-TAG780, which showed homology with genes encoding bZIP transcription factors. The functional ORF included in frame an inner one ATG273-TAG780, which was sufficient to induce HR in plants. CfIINN11 induced plant HR in a dose-dependent manner. CfHNNIl-induced necrosis in NahG transgenic tomato plants was significantly stronger than that in their wild type controls. However, the necrosis in Nr and defl tomato mutants was similar to that in their corresponding wild type plants. These data demonstrate that induction of HR and nonhost resistance by CfHNNI1 is negatively regulated by salicylic acid signalling pathway but independent of ethylene and jasmonic acid signalling pathways.展开更多
Xanthomonas oryzae pv.oryzae(Xoo),the causal agent of bacterial leaf blight in rice,delivers transcription activator-like effector(TALE)proteins into host cells to activate susceptibility or resistance(R)genes that pr...Xanthomonas oryzae pv.oryzae(Xoo),the causal agent of bacterial leaf blight in rice,delivers transcription activator-like effector(TALE)proteins into host cells to activate susceptibility or resistance(R)genes that promote disease or immunity,respectively.Nonhost plants serve as potential reservoirs of R genes;consequently,nonhost R genes may trap TALEs to trigger an immune response.In this study,we screened 17 Xoo TALEs for their ability to induce a hypersensitive response(HR)in the nonhost plant Nicotiana benthamiana(Nb);only AvrXa10 elicited an HR when transiently expressed in Nb.The HR generated by AvrXa10 required both the central repeat region and the activation domain,suggesting a specific interaction between AvrXa10 and a potential R-like gene in nonhost plants.Evans blue staining and ion leakage measurements confirmed that the AvrXa10-triggered HR was a form of cell death,and the transient expression of AvrXa10 in Nb induced immune responses.Genes targeted by AvrXa10 in the Nb genome were identified by transcriptome profiling and prediction of effector binding sites.Using several approaches(in vivo reporter assays,electrophoretic mobility-shift assays,targeted designer TALEs,and on-spot gene silencing),we confirmed that AvrXa10 targets NbZnFP1,a C2H2-type zinc finger protein that resides in the nucleus.Functional analysis indicated that overexpression of NbZnFP1 and its rice orthologs triggered cell death in rice protoplasts.An NbZnFP1 ortholog was also identified in tomato and was specifically activated by AvrXa10.These results demonstrate that NbZnFP1 is a nonhost R gene that traps AvrXa10 to promote plant immunity in Nb.展开更多
Plants are exposed to many potentially pathogenic microbes in the environment, but each species is only susceptible to a limited number of pathogens. The broad resistance is referred to as nonhost re-sistance. To date...Plants are exposed to many potentially pathogenic microbes in the environment, but each species is only susceptible to a limited number of pathogens. The broad resistance is referred to as nonhost re-sistance. To date, little is known about the underlying mechanism of nonhost resistance and the sig-naling transduction process. Here we describe a simple method for isolating Arabidopsis nonhost re-sistance mutants against a nonadapted bacterial pathogen. A RAP2.6 promoter-driven LUC reporter system was developed to replace the tedious bacterial growth assay during the primary screening. The RAP2.6-LUC reporter gene is normally induced by the virulent bacterium Pseudomonas syringae pv tomato but not the nonadapted bacterium P. syringae pv phaseolicola. By using this method we iso-lated 4 mutants displaying strong reporter activity in response to P. syringae pv phaseolicola, which were characterized in some details. ebs1, ebs2, ebs3, and ebs4 (enhanced bacterial susceptibility) were compromised in resistance against P. syringae pv phaseolicola and/or P. syringae pv tomato. In addi-tion, ebs4 showed enhanced hypersensitive response to the incompatible bacterium P. syringae pv tomato (avrB). These results demonstrated that the method is suited for large scale screening for nonhost resistance mutants.展开更多
Tree colonization and feeding activity of the invasive wood-borer Asian longhorn beetle （Anoplophora glabripennis）, an Asian pest introduced into North America and Europe, was studied in a newly invaded area in Ital...Tree colonization and feeding activity of the invasive wood-borer Asian longhorn beetle （Anoplophora glabripennis）, an Asian pest introduced into North America and Europe, was studied in a newly invaded area in Italy. The hypothesis be- ing tested was that the reproductive success of the insect depend on habitat type and tree suitability. Adult beetles were caged on branches of host and nonhost species, in both urban and forest habitats. Two months later, number and size of feeding patches on plant tissues, eggs laid, and surviving larvae were assessed. Bark concentration of C and N was also measured from the same trees. Results indicated that the mean area of plant tissues consumed by adult feeding was significantly larger on trees growing in forest than in urban habitat, although within the same habitat there were no differences between susceptible and nonsusceptible trees. ALB tree colonization, in terms of number of eggs laid and young larvae survival, was not affected by habitat while it was higher on susceptible trees. Although trees growing in forests had a lower nitrogen concentration, they allowed colo- nization rates similar to those of trees growing in the urban habitat. Hence, the amount of carbon and nitrogen did not fully explain tree suitability or habitat selection. We suggest compensatory feeding as a potential mechanism that might explain this peculiar situation, as supported by a more intensive feeding activity recorded on trees in the forest. Suitability of different trees may be due to other factors, such as secondary chemical compounds.展开更多
Hyphal cell wall crude elicitor(CWE)of rice blast pathogen could induce hypersensitive response in tobacco and induce other nonhost plants to be resistant to other fungal pathogens.When corn was treated with CWE,they ...Hyphal cell wall crude elicitor(CWE)of rice blast pathogen could induce hypersensitive response in tobacco and induce other nonhost plants to be resistant to other fungal pathogens.When corn was treated with CWE,they inhibited the infection of Exserohilum turcicum and Curvularia lunata,and when plants of capsicum and cucumber were treated with CWE,they inhibited the infection of Colletotrichum gloeospori-oides.CWE solution showed no bioactivity on spore germination and hyphal growth of the experiment fungi in vitro.Nonhost resistance induced by CWE to other fungal pathogens was not complete resistance.The induced resistant effect(IRE)increased as CWE concentration increased,however,IRE had somehow satura-ted concentration of CWE.Induced nonhost resistance by incompatible pathogen was quantitative to other compatible pathogens.The induced resistance was best at 2 or 3 d after CWE treatment,and then decreased.IRE was about 20 percent in 10 d after CWE treatment.展开更多
基金financially supported by grants from the National Basic Research Program of China (2009CB119000)the Genetically Modified Organisms Breeding Major Projects (2009ZX08009-044B)+2 种基金the PCSIRT Project (IRT0943)the Fundamental Research Funds for the Central Universities (2011XZZX006)the Program for New Century 151 Talents of Zhejiang Province, China
文摘Nonhost resistance is a phenomenon that enables plants to protect themselves against the majority of potential pathogens, and thus has a great potential for application in plant protection. We recently found that CfHNNI1 （for Cladosporium fulvum host and nonhost plant necrosis inducer 1） is an inducer of plant hypersensitive response （HR） and nonhost resistance. In this study, its functional mechanism was analyzed. CfHNN11 was a single copy gene in C. fulvum genome. The functional ORF of the CfHNN11 cDNA was ATG3-TAG780, which showed homology with genes encoding bZIP transcription factors. The functional ORF included in frame an inner one ATG273-TAG780, which was sufficient to induce HR in plants. CfIINN11 induced plant HR in a dose-dependent manner. CfHNNIl-induced necrosis in NahG transgenic tomato plants was significantly stronger than that in their wild type controls. However, the necrosis in Nr and defl tomato mutants was similar to that in their corresponding wild type plants. These data demonstrate that induction of HR and nonhost resistance by CfHNNI1 is negatively regulated by salicylic acid signalling pathway but independent of ethylene and jasmonic acid signalling pathways.
基金This work was supported by the National Natural Science Foundation of China(31830072)the National Key Research and Development Program of China(2016YFD0100601)the National Transgenic Major Program(2016ZX08001-002).
文摘Xanthomonas oryzae pv.oryzae(Xoo),the causal agent of bacterial leaf blight in rice,delivers transcription activator-like effector(TALE)proteins into host cells to activate susceptibility or resistance(R)genes that promote disease or immunity,respectively.Nonhost plants serve as potential reservoirs of R genes;consequently,nonhost R genes may trap TALEs to trigger an immune response.In this study,we screened 17 Xoo TALEs for their ability to induce a hypersensitive response(HR)in the nonhost plant Nicotiana benthamiana(Nb);only AvrXa10 elicited an HR when transiently expressed in Nb.The HR generated by AvrXa10 required both the central repeat region and the activation domain,suggesting a specific interaction between AvrXa10 and a potential R-like gene in nonhost plants.Evans blue staining and ion leakage measurements confirmed that the AvrXa10-triggered HR was a form of cell death,and the transient expression of AvrXa10 in Nb induced immune responses.Genes targeted by AvrXa10 in the Nb genome were identified by transcriptome profiling and prediction of effector binding sites.Using several approaches(in vivo reporter assays,electrophoretic mobility-shift assays,targeted designer TALEs,and on-spot gene silencing),we confirmed that AvrXa10 targets NbZnFP1,a C2H2-type zinc finger protein that resides in the nucleus.Functional analysis indicated that overexpression of NbZnFP1 and its rice orthologs triggered cell death in rice protoplasts.An NbZnFP1 ortholog was also identified in tomato and was specifically activated by AvrXa10.These results demonstrate that NbZnFP1 is a nonhost R gene that traps AvrXa10 to promote plant immunity in Nb.
基金the Shanghai Leading Academic Discipline Project (Grant No. B209)a grant from Chinese Ministry of Science and Technology to Zhou Jian Min (Grant No. 2003AA210080)
文摘Plants are exposed to many potentially pathogenic microbes in the environment, but each species is only susceptible to a limited number of pathogens. The broad resistance is referred to as nonhost re-sistance. To date, little is known about the underlying mechanism of nonhost resistance and the sig-naling transduction process. Here we describe a simple method for isolating Arabidopsis nonhost re-sistance mutants against a nonadapted bacterial pathogen. A RAP2.6 promoter-driven LUC reporter system was developed to replace the tedious bacterial growth assay during the primary screening. The RAP2.6-LUC reporter gene is normally induced by the virulent bacterium Pseudomonas syringae pv tomato but not the nonadapted bacterium P. syringae pv phaseolicola. By using this method we iso-lated 4 mutants displaying strong reporter activity in response to P. syringae pv phaseolicola, which were characterized in some details. ebs1, ebs2, ebs3, and ebs4 (enhanced bacterial susceptibility) were compromised in resistance against P. syringae pv phaseolicola and/or P. syringae pv tomato. In addi-tion, ebs4 showed enhanced hypersensitive response to the incompatible bacterium P. syringae pv tomato (avrB). These results demonstrated that the method is suited for large scale screening for nonhost resistance mutants.
文摘Tree colonization and feeding activity of the invasive wood-borer Asian longhorn beetle （Anoplophora glabripennis）, an Asian pest introduced into North America and Europe, was studied in a newly invaded area in Italy. The hypothesis be- ing tested was that the reproductive success of the insect depend on habitat type and tree suitability. Adult beetles were caged on branches of host and nonhost species, in both urban and forest habitats. Two months later, number and size of feeding patches on plant tissues, eggs laid, and surviving larvae were assessed. Bark concentration of C and N was also measured from the same trees. Results indicated that the mean area of plant tissues consumed by adult feeding was significantly larger on trees growing in forest than in urban habitat, although within the same habitat there were no differences between susceptible and nonsusceptible trees. ALB tree colonization, in terms of number of eggs laid and young larvae survival, was not affected by habitat while it was higher on susceptible trees. Although trees growing in forests had a lower nitrogen concentration, they allowed colo- nization rates similar to those of trees growing in the urban habitat. Hence, the amount of carbon and nitrogen did not fully explain tree suitability or habitat selection. We suggest compensatory feeding as a potential mechanism that might explain this peculiar situation, as supported by a more intensive feeding activity recorded on trees in the forest. Suitability of different trees may be due to other factors, such as secondary chemical compounds.
文摘Hyphal cell wall crude elicitor(CWE)of rice blast pathogen could induce hypersensitive response in tobacco and induce other nonhost plants to be resistant to other fungal pathogens.When corn was treated with CWE,they inhibited the infection of Exserohilum turcicum and Curvularia lunata,and when plants of capsicum and cucumber were treated with CWE,they inhibited the infection of Colletotrichum gloeospori-oides.CWE solution showed no bioactivity on spore germination and hyphal growth of the experiment fungi in vitro.Nonhost resistance induced by CWE to other fungal pathogens was not complete resistance.The induced resistant effect(IRE)increased as CWE concentration increased,however,IRE had somehow satura-ted concentration of CWE.Induced nonhost resistance by incompatible pathogen was quantitative to other compatible pathogens.The induced resistance was best at 2 or 3 d after CWE treatment,and then decreased.IRE was about 20 percent in 10 d after CWE treatment.
