The original online version of this article (Ghozlan, M.H., EL-Argawy, E., Tokgöz, S., Lakshman, D.K. and Mitra, A. (2020) Plant Defense against Necrotrophic Pathogens. American Journal of Plant Sciences, 11, 212...The original online version of this article (Ghozlan, M.H., EL-Argawy, E., Tokgöz, S., Lakshman, D.K. and Mitra, A. (2020) Plant Defense against Necrotrophic Pathogens. American Journal of Plant Sciences, 11, 2122-2138. https://doi.org/10.4236/ajps.2020.1112149) was published mistakenly without another co-author, Nikita Gambhir. In this regard, we revise authors and “how to cite” sections by adding her name.展开更多
Production of reactive oxygen species(ROS)is a conserved immune response primarily mediated by NADPH oxidases(NOXs),also known in plants as respiratory burst oxidase homologs(RBOHs).Most microbe-associated molecular p...Production of reactive oxygen species(ROS)is a conserved immune response primarily mediated by NADPH oxidases(NOXs),also known in plants as respiratory burst oxidase homologs(RBOHs).Most microbe-associated molecular patterns(MAMPs)trigger a very fast and transient ROS burst in plants.However,recently,we found that lipopolysaccharides(LPS),a typical bacterial MAMP,triggered a biphasic ROS burst.In this study,we isolated mutants defective in LPS-triggered biphasic ROS burst(delt)in Arabidopsis,and cloned the DELT1 gene that was shown to encode RBOHD.In the delt1-2 allele,the antepenultimate residue,glutamic acid(E919),at the C-terminus of RBOHD was mutated to lysine(K).E919 is a highly conserved residue in NADPH oxidases,and a mutation of the corresponding residue E568 in human NOX2 has been reported to be one of the causes of chronic granulomatous disease.Consistently,we found that residue E919 was indispensable for RBOHD function in the MAMP-induced ROS burst and stomatal closure.It has been suggested that the mutation of this residue in other NADPH oxidases impairs the protein’s stability and complex assembly.However,we found that the E919K mutation did not affect RBOHD protein abundance or the ability of protein association,suggesting that the residue E919 in RBOHD might have a regulatory mechanism different from that of other NOXs.Taken together,our results confirm that the antepenultimate residue E is critical for NADPH oxidases and provide a new insight into the regulatory mechanisms of RBOHD.展开更多
Necrotrophic pathogenic bacteria, fungi and oomycetes are widely distributed and are responsible for significant crop losses. Host plants deploy different defense mechanisms and appropriate immune responses to defend ...Necrotrophic pathogenic bacteria, fungi and oomycetes are widely distributed and are responsible for significant crop losses. Host plants deploy different defense mechanisms and appropriate immune responses to defend them against these pathogens. Regardless of the pathogen’s lifestyle, infection activates plant immune responses either through Pathogen/Microbe Associated Molecular Pattern (P/MAMP) or through Effector Triggered Immunity (ETI). However, as R-genes are not usually associated with resistance to necrotrophs, resistance is largely dependent on the balanced interplay between crucial phytohormones in complex signaling pathways involving jasmonic acid (JA), ethylene, salicylic acid (SA) and abscisic acid (ABA). An increase in salicylic acid levels enhances susceptibility to necrotrophic pathogens but promotes resistance to hemibiotrophs, whereas a deficiency in SA or SA signaling has either no significant impact or affects resistance only at the primary infection site. The same fashion is observed for JA signaling system that appears to elicit resistance against diseases caused by necrotrophic pathogens and can trigger systemic immunity conferring resistance against them. On the other hand, ABA can play a positive or negative role in plant defense responses to necrotrophs as ABA-mediated defense responses are dependent on specific plant-pathogen interactions. Understanding plant immune response against necrotrophic pathogens may lead to the development of resistant or tolerant crop cultivars.展开更多
The flagellin-sensing mechanism is one of the most extensively studied topics in plant defense systems.This widespread interest arises from the ability of flagellin to trigger robust and extensive responses,establishi...The flagellin-sensing mechanism is one of the most extensively studied topics in plant defense systems.This widespread interest arises from the ability of flagellin to trigger robust and extensive responses,establishing it as a cornerstone for research into other defense mechanisms.Plants recognize bacterial flagellin epitopes through plasma-membrane-localized pattern-recognition receptors,initiating pattern-triggered immunity as the frontline defense against bacterial pathogens.In this review,we comprehensively summarize flagellin-sensing mechanisms and signal transduction pathways in plants.We compare the flagellin-sensing mechanisms of plants and mammals,focusing on epitope processing and recognition.We present detailed downstream signaling events,from receptor complex formation to transcriptional reprogramming.Furthermore,we highlight the evolutionary arms race between plants and bacteria and incorporate emerging insights into how flagellin-triggered responses are modulated by receptor networking,phytocytokines,and environmental factors.These findings suggest that flagellin-mediated immune responses are highly dynamic and context dependent.By synthesizing current knowledge and recent discoveries,this review provides updated perspectives on plant–microbe interactions and aims to inspire future research in plant immunity.展开更多
Under nutrient-limiting conditions, plants will enter into symbiosis with arbuscular mycorrhizal （AM） fungi for the enhancement of mineral nutrient acquisition from the surrounding soil. AM fungi live in close, intr...Under nutrient-limiting conditions, plants will enter into symbiosis with arbuscular mycorrhizal （AM） fungi for the enhancement of mineral nutrient acquisition from the surrounding soil. AM fungi live in close, intracellular association with plant roots where they transfer phosphate and nitrogen to the plant in exchange for carbon. They are obligate fungi, relying on their host as their only carbon source. Much has been discovered in the last decade concerning the signaling events during initiation of the AM symbiosis, including the identification of signaling molecules generated by both partners. This signaling occurs through symbiosis-specific gene products in the host plant, which are indispensable for normal AM development. At the same time, plants have adapted complex mechanisms for avoiding infection by pathogenic fungi, including an innate immune response to general microbial molecules, such as chitin present in fungal cell walls. How it is that AM fungal colonization is maintained without eliciting a defensive response from the host is still uncertain. In this review, we present a summary of the molecular signals and their elicited responses during initiation of the AM symbiosis, including plant immune responses and their suppression.展开更多
MYB34, MYB51, and MYB122 transcription factors are known as decisive regulators of indolic glucosinolate （IG） biosynthesis with a strong impact on expression of genes encoding CYP79B2 and CYP79B3 enzymes that redund...MYB34, MYB51, and MYB122 transcription factors are known as decisive regulators of indolic glucosinolate （IG） biosynthesis with a strong impact on expression of genes encoding CYP79B2 and CYP79B3 enzymes that redundantly convert tryptophan to indole-3-acetaldoxime （IAOx）. This intermediate represents a branching point for IG biosynthesis, and pathways leading to camalexin and indole-carboxylic acids （ICA）. Here we investigate how these MYBs affect the pathogen-triggered Trp metabolism. Our experiments indicated that these three MYBs affect not only IG production but also constitutive biosynthesis of other IAOx- derived metabolites. Strikingly, the PENETRATION 2 （PEN2）-dependent IG-metabolism products, which are absent in myb34/51/122 and pen2 mutants, were indispensable for full flg22-mediated induction of other IAOx-dedved compounds. However, germ induction and accumulation of ICAs and camalexin upon path- ogen infection was not compromised in myb34/51/122 plants, despite strongly reduced IG levels. Hence, in comparison with cyp79B2/B3, which lacks all IAOx-derived metabolites, we found myb34/51/122 an ideal tool to analyze IG contribution to resistance against the necrotrophic fungal pathogen Plectosphaerella cucumerina. The susceptibility of myb34/51/122 was similar to that of pen2, but much lower than susceptibility of cyp79B2/B3, indicating that MYB34/51/122 contribute to resistance toward P. cucumerina exclu- sively through IG biosynthesis, and that PEN2 is the main leaf myrosinase activating IGs in response to microbial pathogens.展开更多
Plants possess innate Immune systems to prevent most potential Infections. The ancient and conserved innate immune responses are triggered by microbe-associated molecular patterns （MAMPs） and play important roles in...Plants possess innate Immune systems to prevent most potential Infections. The ancient and conserved innate immune responses are triggered by microbe-associated molecular patterns （MAMPs） and play important roles in broad-spectrum defenses. However, successful bacterial pathogens evolved type Ⅲ virulence effectors to suppress MAMP-medlated immunity. To survive, plants further developed highly specific resistance （R） genes to trigger gene-for-gene-mediated immunity and turn the virulent pathogens into avirulent ones. We summarize here the very recent advances in this dynamic coevolution of plantbacterium interaction.展开更多
Verticillium wilt diseases caused by the soil-borne fungus Verticillium dahliae result in devastating yield losses in many economically important crops annually. Here, we identified a novel ethyleneinducing xylanase(E...Verticillium wilt diseases caused by the soil-borne fungus Verticillium dahliae result in devastating yield losses in many economically important crops annually. Here, we identified a novel ethyleneinducing xylanase(EIX)-like protein, VdEIX3, from V. dahliae, which exhibits immunity-inducing activity in Nicotiana benthamiana. In vitro-purified VdEIX3 can induce strong oxidative burst, activate the expression of defense-related genes, and increase resistance against oomycete and fungal pathogens in N. benthamiana. VdEIX3 orthologs of other Verticillium pathogens also induce cell death in N. benthamiana, which form a new type of EIX protein family that is distinct from the known EIX proteins. A leucine-rich repeat receptor-like protein, NbEIX2, regulates the perception of VdEIX3 in N. benthamiana. Our results demonstrate that VdEIX3 is a novel EIX-like protein that can be recognized by N. benthamiana NbEIX2, and also suggest that NbEIX2 is a promising receptor-like protein that is potentially applicable to transgenic breeding for improving resistance to Verticillium wilt diseases.展开更多
Mitogen-activated protein kinase(MAPK) cascades play pivotal roles in plant defense against phytopathogens downstream of immune receptor complexes. The amplitude and duration of MAPK activation must be strictly contro...Mitogen-activated protein kinase(MAPK) cascades play pivotal roles in plant defense against phytopathogens downstream of immune receptor complexes. The amplitude and duration of MAPK activation must be strictly controlled, but the underlying mechanism remains unclear. Here, we identified Arabidopsis CPL1(C-terminal domain phosphatase-like 1)as a negative regulator of microbe-associated molecular pattern(MAMP)-triggered immunity via a forward-genetic screen. Disruption of CPL1 significantly enhanced plant resistance to Pseudomonas pathogens induced by the bacterial peptide fg22. Furthermore, fg22-induced MPK3/MPK4/MPK6 phosphorylation was dramatically elevated in cpl1 mutants but severely impaired in CPL1 overexpression lines, suggesting that CPL1 might interfere with fg22-induced MAPK activation. Indeed, CPL1 directly interacted with MPK3 and MPK6, as well as the upstream MKK4 and MKK5. A firefy luciferase-based complementation assay indicated that the interaction between MKK4/MKK5 and MPK3/MPK6 was significantly reduced in the presence of CPL1. These results suggest that CPL1 plays a novel regulatory role in suppressing MAMP-induced MAPK cascade activation and MAMP-triggered immunity to bacterial pathogens.展开更多
文摘The original online version of this article (Ghozlan, M.H., EL-Argawy, E., Tokgöz, S., Lakshman, D.K. and Mitra, A. (2020) Plant Defense against Necrotrophic Pathogens. American Journal of Plant Sciences, 11, 2122-2138. https://doi.org/10.4236/ajps.2020.1112149) was published mistakenly without another co-author, Nikita Gambhir. In this regard, we revise authors and “how to cite” sections by adding her name.
基金the National Natural Science Foundation of China(No.31622006)the Postdoctoral Science Foundation of China(Nos.2018M630683 and 2018T110601)
文摘Production of reactive oxygen species(ROS)is a conserved immune response primarily mediated by NADPH oxidases(NOXs),also known in plants as respiratory burst oxidase homologs(RBOHs).Most microbe-associated molecular patterns(MAMPs)trigger a very fast and transient ROS burst in plants.However,recently,we found that lipopolysaccharides(LPS),a typical bacterial MAMP,triggered a biphasic ROS burst.In this study,we isolated mutants defective in LPS-triggered biphasic ROS burst(delt)in Arabidopsis,and cloned the DELT1 gene that was shown to encode RBOHD.In the delt1-2 allele,the antepenultimate residue,glutamic acid(E919),at the C-terminus of RBOHD was mutated to lysine(K).E919 is a highly conserved residue in NADPH oxidases,and a mutation of the corresponding residue E568 in human NOX2 has been reported to be one of the causes of chronic granulomatous disease.Consistently,we found that residue E919 was indispensable for RBOHD function in the MAMP-induced ROS burst and stomatal closure.It has been suggested that the mutation of this residue in other NADPH oxidases impairs the protein’s stability and complex assembly.However,we found that the E919K mutation did not affect RBOHD protein abundance or the ability of protein association,suggesting that the residue E919 in RBOHD might have a regulatory mechanism different from that of other NOXs.Taken together,our results confirm that the antepenultimate residue E is critical for NADPH oxidases and provide a new insight into the regulatory mechanisms of RBOHD.
文摘Necrotrophic pathogenic bacteria, fungi and oomycetes are widely distributed and are responsible for significant crop losses. Host plants deploy different defense mechanisms and appropriate immune responses to defend them against these pathogens. Regardless of the pathogen’s lifestyle, infection activates plant immune responses either through Pathogen/Microbe Associated Molecular Pattern (P/MAMP) or through Effector Triggered Immunity (ETI). However, as R-genes are not usually associated with resistance to necrotrophs, resistance is largely dependent on the balanced interplay between crucial phytohormones in complex signaling pathways involving jasmonic acid (JA), ethylene, salicylic acid (SA) and abscisic acid (ABA). An increase in salicylic acid levels enhances susceptibility to necrotrophic pathogens but promotes resistance to hemibiotrophs, whereas a deficiency in SA or SA signaling has either no significant impact or affects resistance only at the primary infection site. The same fashion is observed for JA signaling system that appears to elicit resistance against diseases caused by necrotrophic pathogens and can trigger systemic immunity conferring resistance against them. On the other hand, ABA can play a positive or negative role in plant defense responses to necrotrophs as ABA-mediated defense responses are dependent on specific plant-pathogen interactions. Understanding plant immune response against necrotrophic pathogens may lead to the development of resistant or tolerant crop cultivars.
基金supported by grants from the Institute for Basic Science(IBS-R021-D1-2025-a00)the National Research Foundation of Korea(RS-2024-00338015)to H.-S.L.and by the Startup Fund from Duke Kunshan University to E.Y.K.D.-H.Lsupported by a postdoctoral fellowship from the National Research Foundation of Korea(NRF-2021R1A6A3A03039464).No conflict of interest is declared.
文摘The flagellin-sensing mechanism is one of the most extensively studied topics in plant defense systems.This widespread interest arises from the ability of flagellin to trigger robust and extensive responses,establishing it as a cornerstone for research into other defense mechanisms.Plants recognize bacterial flagellin epitopes through plasma-membrane-localized pattern-recognition receptors,initiating pattern-triggered immunity as the frontline defense against bacterial pathogens.In this review,we comprehensively summarize flagellin-sensing mechanisms and signal transduction pathways in plants.We compare the flagellin-sensing mechanisms of plants and mammals,focusing on epitope processing and recognition.We present detailed downstream signaling events,from receptor complex formation to transcriptional reprogramming.Furthermore,we highlight the evolutionary arms race between plants and bacteria and incorporate emerging insights into how flagellin-triggered responses are modulated by receptor networking,phytocytokines,and environmental factors.These findings suggest that flagellin-mediated immune responses are highly dynamic and context dependent.By synthesizing current knowledge and recent discoveries,this review provides updated perspectives on plant–microbe interactions and aims to inspire future research in plant immunity.
基金Financial support for this research program was provided by the US National Science Foundation (IOS‐0842720)an award from the US National Science Foundation Graduate Research Fellowship (DGE‐1144153)
文摘Under nutrient-limiting conditions, plants will enter into symbiosis with arbuscular mycorrhizal （AM） fungi for the enhancement of mineral nutrient acquisition from the surrounding soil. AM fungi live in close, intracellular association with plant roots where they transfer phosphate and nitrogen to the plant in exchange for carbon. They are obligate fungi, relying on their host as their only carbon source. Much has been discovered in the last decade concerning the signaling events during initiation of the AM symbiosis, including the identification of signaling molecules generated by both partners. This signaling occurs through symbiosis-specific gene products in the host plant, which are indispensable for normal AM development. At the same time, plants have adapted complex mechanisms for avoiding infection by pathogenic fungi, including an innate immune response to general microbial molecules, such as chitin present in fungal cell walls. How it is that AM fungal colonization is maintained without eliciting a defensive response from the host is still uncertain. In this review, we present a summary of the molecular signals and their elicited responses during initiation of the AM symbiosis, including plant immune responses and their suppression.
文摘MYB34, MYB51, and MYB122 transcription factors are known as decisive regulators of indolic glucosinolate （IG） biosynthesis with a strong impact on expression of genes encoding CYP79B2 and CYP79B3 enzymes that redundantly convert tryptophan to indole-3-acetaldoxime （IAOx）. This intermediate represents a branching point for IG biosynthesis, and pathways leading to camalexin and indole-carboxylic acids （ICA）. Here we investigate how these MYBs affect the pathogen-triggered Trp metabolism. Our experiments indicated that these three MYBs affect not only IG production but also constitutive biosynthesis of other IAOx- derived metabolites. Strikingly, the PENETRATION 2 （PEN2）-dependent IG-metabolism products, which are absent in myb34/51/122 and pen2 mutants, were indispensable for full flg22-mediated induction of other IAOx-dedved compounds. However, germ induction and accumulation of ICAs and camalexin upon path- ogen infection was not compromised in myb34/51/122 plants, despite strongly reduced IG levels. Hence, in comparison with cyp79B2/B3, which lacks all IAOx-derived metabolites, we found myb34/51/122 an ideal tool to analyze IG contribution to resistance against the necrotrophic fungal pathogen Plectosphaerella cucumerina. The susceptibility of myb34/51/122 was similar to that of pen2, but much lower than susceptibility of cyp79B2/B3, indicating that MYB34/51/122 contribute to resistance toward P. cucumerina exclu- sively through IG biosynthesis, and that PEN2 is the main leaf myrosinase activating IGs in response to microbial pathogens.
基金Publication of this paper is supported by the National Natural Science Foundation of China （30624808） and Science Publication Foundation of the Chinese Academy of Sciences.
文摘Plants possess innate Immune systems to prevent most potential Infections. The ancient and conserved innate immune responses are triggered by microbe-associated molecular patterns （MAMPs） and play important roles in broad-spectrum defenses. However, successful bacterial pathogens evolved type Ⅲ virulence effectors to suppress MAMP-medlated immunity. To survive, plants further developed highly specific resistance （R） genes to trigger gene-for-gene-mediated immunity and turn the virulent pathogens into avirulent ones. We summarize here the very recent advances in this dynamic coevolution of plantbacterium interaction.
基金This study was supported by the Fundamental Research Funds for the Central Universities(KYLH201703)the National Natural Science Foundation of China(31625023)。
文摘Verticillium wilt diseases caused by the soil-borne fungus Verticillium dahliae result in devastating yield losses in many economically important crops annually. Here, we identified a novel ethyleneinducing xylanase(EIX)-like protein, VdEIX3, from V. dahliae, which exhibits immunity-inducing activity in Nicotiana benthamiana. In vitro-purified VdEIX3 can induce strong oxidative burst, activate the expression of defense-related genes, and increase resistance against oomycete and fungal pathogens in N. benthamiana. VdEIX3 orthologs of other Verticillium pathogens also induce cell death in N. benthamiana, which form a new type of EIX protein family that is distinct from the known EIX proteins. A leucine-rich repeat receptor-like protein, NbEIX2, regulates the perception of VdEIX3 in N. benthamiana. Our results demonstrate that VdEIX3 is a novel EIX-like protein that can be recognized by N. benthamiana NbEIX2, and also suggest that NbEIX2 is a promising receptor-like protein that is potentially applicable to transgenic breeding for improving resistance to Verticillium wilt diseases.
基金supported by the National Natural Science Foundation of China (grant no. 31671991 to FC)。
文摘Mitogen-activated protein kinase(MAPK) cascades play pivotal roles in plant defense against phytopathogens downstream of immune receptor complexes. The amplitude and duration of MAPK activation must be strictly controlled, but the underlying mechanism remains unclear. Here, we identified Arabidopsis CPL1(C-terminal domain phosphatase-like 1)as a negative regulator of microbe-associated molecular pattern(MAMP)-triggered immunity via a forward-genetic screen. Disruption of CPL1 significantly enhanced plant resistance to Pseudomonas pathogens induced by the bacterial peptide fg22. Furthermore, fg22-induced MPK3/MPK4/MPK6 phosphorylation was dramatically elevated in cpl1 mutants but severely impaired in CPL1 overexpression lines, suggesting that CPL1 might interfere with fg22-induced MAPK activation. Indeed, CPL1 directly interacted with MPK3 and MPK6, as well as the upstream MKK4 and MKK5. A firefy luciferase-based complementation assay indicated that the interaction between MKK4/MKK5 and MPK3/MPK6 was significantly reduced in the presence of CPL1. These results suggest that CPL1 plays a novel regulatory role in suppressing MAMP-induced MAPK cascade activation and MAMP-triggered immunity to bacterial pathogens.
