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Oome S, Van den Ackerveken G. Comparative and functional analysis of the widely occurring family of Nep1-like proteins. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2014; 27:1081-94. [PMID: 25025781 DOI: 10.1094/mpmi-04-14-0118-r] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Nep1-like proteins (NLP) are best known for their cytotoxic activity in dicot plants. NLP are taxonomically widespread among microbes with very different lifestyles. To learn more about this enigmatic protein family, we analyzed more than 500 available NLP protein sequences from fungi, oomycetes, and bacteria. Phylogenetic clustering showed that, besides the previously documented two types, an additional, more divergent, third NLP type could be distinguished. By closely examining the three NLP types, we identified a noncytotoxic subgroup of type 1 NLP (designated type 1a), which have substitutions in amino acids making up a cation-binding pocket that is required for cytotoxicity. Type 2 NLP were found to contain a putative calcium-binding motif, which was shown to be required for cytotoxicity. Members of both type 1 and type 2 NLP were found to possess additional cysteine residues that, based on their predicted proximity, make up potential disulfide bridges that could provide additional stability to these secreted proteins. Type 1 and type 2 NLP, although both cytotoxic to plant cells, differ in their ability to induce necrosis when artificially targeted to different cellular compartments in planta, suggesting they have different mechanisms of cytotoxicity.
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Zhou BJ, Jia PS, Gao F, Guo HS. Molecular characterization and functional analysis of a necrosis- and ethylene-inducing, protein-encoding gene family from Verticillium dahliae. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:964-75. [PMID: 22414440 DOI: 10.1094/mpmi-12-11-0319] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Verticillium dahliae Kleb. is a hemibiotrophic, phytopathogenic fungus that causes wilt disease in a wide range of crops, including cotton. Successful host colonization by hemibiotrophic pathogens requires the induction of plant cell death to provide the saprophytic nutrition for the transition from the biotrophic to the necrotrophic stage. In this study, we identified a necrosis-inducing Phytophthora protein (NPP1) domain-containing protein family containing nine genes in a virulent, defoliating isolate of V. dahliae (V592), named the VdNLP genes. Functional analysis demonstrated that only two of these VdNLP genes, VdNLP1 and VdNLP2, encoded proteins that were capable of inducing necrotic lesions and triggering defense responses in Nicotiana benthamiana, Arabidopsis, and cotton plants. Both VdNLP1 and VdNLP2 induced the wilting of cotton seedling cotyledons. However, gene-deletion mutants targeted by VdNLP1, VdNLP2, or both did not affect the pathogenicity of V. dahliae V592 in cotton infection. Similar expression and induction patterns were found for seven of the nine VdNLP transcripts. Through a comparison of the conserved amino acid residues of VdNLP with different necrosis-inducing activities, combined with mutagenesis-based analyses, we identified several novel conserved amino acid residues, in addition to the known conserved heptapeptide GHRHDWE motif and the cysteine residues of the NPP domain-containing protein, that are indispensable for the necrosis-inducing activity of the VdNLP2 protein.
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Affiliation(s)
- Bang-Jun Zhou
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
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Cabral A, Oome S, Sander N, Küfner I, Nürnberger T, Van den Ackerveken G. Nontoxic Nep1-like proteins of the downy mildew pathogen Hyaloperonospora arabidopsidis: repression of necrosis-inducing activity by a surface-exposed region. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:697-708. [PMID: 22235872 DOI: 10.1094/mpmi-10-11-0269] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The genome of the downy mildew pathogen Hyaloperonospora arabidopsidis encodes necrosis and ethylene-inducing peptide 1 (Nep1)-like proteins (NLP). Although NLP are widely distributed in eukaryotic and prokaryotic plant pathogens, it was surprising to find these proteins in the obligate biotrophic oomycete H. arabidopsidis. Therefore, we analyzed the H. arabidopsidis NLP (HaNLP) family and identified 12 HaNLP genes and 15 pseudogenes. Most of the 27 genes form an H. arabidopsidis-specific cluster when compared with other oomycete NLP genes, suggesting this class of effectors has recently expanded in H. arabidopsidis. HaNLP transcripts were mainly detected during early infection stages. Agrobacterium tumefaciens-mediated transient expression and infiltration of recombinant NLP into tobacco and Arabidopsis leaves revealed that all HaNLP tested are noncytotoxic proteins. Even HaNLP3, which is most similar to necrosis-inducing NLP proteins of other oomycetes and which contains all amino acids that are critical for necrosis-inducing activity, did not induce necrosis. Chimeras constructed between HaNLP3 and the necrosis-inducing PsojNIP protein demonstrated that most of the HaNLP3 protein is functionally equivalent to PsojNIP, except for an exposed domain that prevents necrosis induction. The early expression and species-specific expansion of the HaNLP genes is suggestive of an alternative function of noncytolytic NLP proteins during biotrophic infection of plants.
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Affiliation(s)
- Adriana Cabral
- Plant-microbe interactions, Department of Biology, Utrecht University, Padualaan 8, 3508 CH Utrecht, The Netherlands
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da Silva LF, Dias CV, Cidade LC, Mendes JS, Pirovani CP, Alvim FC, Pereira GAG, Aragão FJL, Cascardo JCM, Costa MGC. Expression of an oxalate decarboxylase impairs the necrotic effect induced by Nep1-like protein (NLP) of Moniliophthora perniciosa in transgenic tobacco. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2011; 24:839-48. [PMID: 21405988 DOI: 10.1094/mpmi-12-10-0286] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Oxalic acid (OA) and Nep1-like proteins (NLP) are recognized as elicitors of programmed cell death (PCD) in plants, which is crucial for the pathogenic success of necrotrophic plant pathogens and involves reactive oxygen species (ROS). To determine the importance of oxalate as a source of ROS for OA- and NLP-induced cell death, a full-length cDNA coding for an oxalate decarboxylase (FvOXDC) from the basidiomycete Flammulina velutipes, which converts OA into CO(2) and formate, was overexpressed in tobacco plants. The transgenic plants contained less OA and more formic acid compared with the control plants and showed enhanced resistance to cell death induced by exogenous OA and MpNEP2, an NLP of the hemibiotrophic fungus Moniliophthora perniciosa. This resistance was correlated with the inhibition of ROS formation in the transgenic plants inoculated with OA, MpNEP2, or a combination of both PCD elicitors. Taken together, these results have established a pivotal function for oxalate as a source of ROS required for the PCD-inducing activity of OA and NLP. The results also indicate that FvOXDC represents a potentially novel source of resistance against OA- and NLP-producing pathogens such as M. perniciosa, the causal agent of witches' broom disease of cacao (Theobroma cacao L.).
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Affiliation(s)
- Leonardo F da Silva
- Centro de Biotecnologia e Genetica, Universidade Estadual de Santa Cruz, Brazil
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Motteram J, Küfner I, Deller S, Brunner F, Hammond-Kosack KE, Nürnberger T, Rudd JJ. Molecular characterization and functional analysis of MgNLP, the sole NPP1 domain-containing protein, from the fungal wheat leaf pathogen Mycosphaerella graminicola. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2009; 22:790-9. [PMID: 19522561 DOI: 10.1094/mpmi-22-7-0790] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Analysis of the fully sequenced genome of the wheat leaf-specific fungal pathogen Mycosphaerella graminicola identified only a single gene encoding a member of the necrosis- and ethylene-inducing peptide 1 (Nep1)-like protein family (NLP). NLP proteins have frequently been shown to trigger cell death and the activation of defense signaling reactions in dicotyledonous plants. However, complete loss-of-function reverse genetics analyses for their importance in the virulence of eukaryotic plant pathogens are generally lacking. Real-time quantitative polymerase chain reaction on MgNLP demonstrated the gene to be specifically expressed in planta. Peak expression was observed during the immediate presymptomatic phase of colonization of a susceptible host genotype. This was followed by a dramatic decrease during disease lesion formation which, in this system, exhibits characteristics of host programmed cell death (PCD). No comparable peak in transcript levels was seen during an incompatible interaction with a host genotype exhibiting gene-for-gene-based disease resistance. Heterologously expressed MgNLP protein induced necrotic cell death and the activation of defense-related genes when infiltrated into Arabidopsis leaves but not in leaves of a susceptible wheat genotype. MgNLP infiltration also failed to stimulate wheat mitogen-activated protein kinase activities. Finally, targeted deletion of M. graminicola MgNLP caused no detectable reduction in plant pathogenicity or virulence, suggesting that this protein is not a major virulence determinant during fungal infection of its host plant. To our knowledge, this represents the first complete loss-of-function analysis of NLP in a eukaryotic plant pathogen and we discuss our findings in the context of possible functions for NLP in pathogens which only infect monocotyledonous plants.
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Affiliation(s)
- Juliet Motteram
- Centre for Sustainable Pest and Disease Management, Department of Plant Pathology and Microbiology, Rothamsted Research, Harpenden, Herts, UK
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Cechin AL, Sinigaglia M, Lemke N, Echeverrigaray S, Cabrera OG, Pereira GAG, Mombach JCM. Cupin: a candidate molecular structure for the Nep1-like protein family. BMC PLANT BIOLOGY 2008; 8:50. [PMID: 18447914 PMCID: PMC2396628 DOI: 10.1186/1471-2229-8-50] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2007] [Accepted: 04/30/2008] [Indexed: 05/10/2023]
Abstract
BACKGROUND NEP1-like proteins (NLPs) are a novel family of microbial elicitors of plant necrosis. Some NLPs induce a hypersensitive-like response in dicot plants though the basis for this response remains unclear. In addition, the spatial structure and the role of these highly conserved proteins are not known. RESULTS We predict a 3d-structure for the beta-rich section of the NLPs based on alignments, prediction tools and molecular dynamics. We calculated a consensus sequence from 42 NLPs proteins, predicted its secondary structure and obtained a high quality alignment of this structure and conserved residues with the two Cupin superfamily motifs. The conserved sequence GHRHDWE and several common residues, especially some conserved histidines, in NLPs match closely the two cupin motifs. Besides other common residues shared by dicot Auxin-Binding Proteins (ABPs) and NLPs, an additional conserved histidine found in all dicot ABPs was also found in all NLPs at the same position. CONCLUSION We propose that the necrosis inducing protein class belongs to the Cupin superfamily. Based on the 3d-structure, we are proposing some possible functions for the NLPs.
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Affiliation(s)
- Adelmo L Cechin
- Programa de Pós-Graduação em Computação Aplicada, Unisinos, Av. Unisinos – 950, São Leopoldo, Brasil
| | - Marialva Sinigaglia
- Programa de Pós-Graduação em Computação Aplicada, Unisinos, Av. Unisinos – 950, São Leopoldo, Brasil
| | - Ney Lemke
- Departamento de Física e Biofísica, UNESP, Dist. Rubião Jr. sn, Botucatu, Brasil
| | - Sérgio Echeverrigaray
- Instituto de Biotecnologia, UCS, R. Francisco Getúlio Vargas 1130, Caxias do Sul, Brasil
| | - Odalys G Cabrera
- Departamento de Genética e Evolução, IB/UNICAMP, Campinas, Brasil
| | | | - José CM Mombach
- Centro de Ciências Rurais, UFPampa/UFSM, São Gabriel, Brasil
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Staats M, VAN Baarlen P, Schouten A, VAN Kan JAL. Functional analysis of NLP genes from Botrytis elliptica. MOLECULAR PLANT PATHOLOGY 2007; 8:209-14. [PMID: 20507492 DOI: 10.1111/j.1364-3703.2007.00382.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
SUMMARY We functionally analysed two Nep1-like protein (NLP) genes from Botrytis elliptica (a specialized pathogen of lily), encoding proteins homologous to the necrosis and ethylene-inducing protein (NEP1) from Fusarium oxysporum. Single gene replacement mutants were made for BeNEP1 and BeNEP2, providing the first example of transformation and successful targeted mutagenesis in this fungus. The virulence of both mutants on lily leaves was not affected. BeNEP1 and BeNEP2 were individually expressed in the yeast Pichia pastoris, and the necrosis-inducing activity was tested by infiltration of both proteins into leaves of several monocots and eudicots. Necrotic symptoms developed on the eudicots tobacco, Nicotiana benthamiana and Arabidopsis thaliana, and cell death was induced in tomato cell suspensions. No necrotic symptoms developed on leaves of the monocots rice, maize and lily. These results support the hypothesis that the necrosis-inducing activity of NLPs is limited to eudicots. We conclude that NLPs are not essential virulence factors and they do not function as host-selective toxins for B. elliptica.
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Affiliation(s)
- Martijn Staats
- Wageningen University, Laboratory of Phytopathology, Wageningen, The Netherlands
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Kanneganti TD, Huitema E, Cakir C, Kamoun S. Synergistic interactions of the plant cell death pathways induced by Phytophthora infestans Nepl-like protein PiNPP1.1 and INF1 elicitin. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:854-63. [PMID: 16903351 DOI: 10.1094/mpmi-19-0854] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Cell death plays a ubiquitous role in plant-microbe interactions, given that it is associated with both susceptible and resistance interactions. A class of cell death-inducing proteins, termed Nepl-like proteins (NLPs), has been reported in bacteria, fungi, and oomycetes. These proteins induce nonspecific necrosis in a variety of dicotyledonous plants. Here, we describe three members of the NLP family from the oomycete Phytophthora infestans (PiNPP1.1, PiNPP1.2, and PiNPP1.3). Using agroinfection with a binary Potato virus X vector, we showed that PiNPP1.1 induces cell death in Nicotiana benthamiana and the host plant tomato. Expression analyses indicated that PiNPP1.1 is up-regulated during late stages of infection of tomato by P. infestans. We compared PiNPP1.1 necrosis-inducing activity to INF1 elicitin, a well-studied protein that triggers the hypersensitive response in Nicotiana spp. Using virus-induced gene silencing, we showed that the cell death induced by PiNPP1.1 is dependent on the ubiquitin ligase-associated protein SGT1 and the heat-shock protein HSP90. In addition, cell death triggered by PiNPP1.1 but not that by INF1 was dependent on the defense-signaling proteins COI1, MEK2, NPR1, and TGA2.2, suggesting distinct signaling requirements. Combined expression of PiNPP1.1 and INF1 in N. benthamiana resulted in enhanced cell death, suggesting synergistic interplay between the two cell-death responses. Altogether, these results point to potentially distinct but interacting cell-death pathways induced by PiNPP1.1 and INF1 in plants.
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Affiliation(s)
- Thirumala-Devi Kanneganti
- Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, 1680 Madison Ave., Wooster, OH 44691, USA
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Sharathchandra RG, Geetha NP, Amruthesh KN, Kini KR, Sarosh BR, Shetty NP, Shetty HS. Isolation and characterisation of a protein elicitor from Sclerospora graminicola and elicitor-mediated induction of defence responses in cultured cells of Pennisetum glaucum. FUNCTIONAL PLANT BIOLOGY : FPB 2006; 33:267-278. [PMID: 32689234 DOI: 10.1071/fp05197] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2005] [Accepted: 10/10/2005] [Indexed: 06/11/2023]
Abstract
Sclerospora graminicola (Sacc.) Schroet., an oomycete pathogen of Pennisetum glaucum (L.) R.Br. infects the meristematic tissues of young seedlings. The motile zoospores from the sporangia encyst, germinate and penetrate the plant tissue. Resistance to the invading pathogen is governed by the specific recognition of conserved pathogen-associated proteins or elicitors. In the present study, a zoospore protein was isolated and purified to homogeneity by a combination of size exclusion and high-performance liquid chromatography (HPLC). The crude fractionated protein was able to elicit an array of defence responses in resistant and susceptible cells of pearl millet. Treatment of cultured cells of pearl millet with partially purified elicitor protein resulted in a rapid loss of cell viability in the resistant cells and the percentage of cell death was higher in the resistant than in the susceptible cells. Cultures of resistant cells showed a sharp increase in the extra cellular pH compared with susceptible cells when treated with the crude elicitor. Increased oxidative burst was also recorded in the cells treated with the crude elicitor. The purified elicitor showed unique properties. The purified protein was acidic with a pI of 5.6 as revealed by isoelectric focusing (IEF) and matrix-assisted laser desorption ionisation (MALDI) analysis showed that the elicitor had a molecular mass of 7040 daltons. The primary structure determined by N-terminal Edman degradation and searches with BLAST did not reveal similarities to any known plant pathogenic or oomycete elicitor. Higher activities of the important defence-related enzymes phenylalanine ammonia lyase (PAL) and peroxidase in the resistant cell cultures than in the susceptible cell cultures treated with the purified elicitor were clearly evident. Studies of gene expression by northern blotting with heterologus peroxidase, PAL and oxalate oxidase probes showed that the mRNA transcripts were strongly up-regulated in resistant cell cultures within 30 min of elicitor treatment. The purified elicitor also demonstrated a very strong concentration-dependent sterol binding. The purified elicitor protein belongs to a class of low molecular weight oomycete elicitors with sterol carrier properties. The identified low molecular weight protein elicitor displays unique properties that can be exploited for synthesis of novel molecules for eco-friendly crop protection.
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Affiliation(s)
- R G Sharathchandra
- Downy Mildew Research Laboratory, Department of Studies in Applied Botany and Biotechnology, University of Mysore, Manasagangotri Mysore-570 006, India
| | - N P Geetha
- Downy Mildew Research Laboratory, Department of Studies in Applied Botany and Biotechnology, University of Mysore, Manasagangotri Mysore-570 006, India
| | - K N Amruthesh
- Downy Mildew Research Laboratory, Department of Studies in Applied Botany and Biotechnology, University of Mysore, Manasagangotri Mysore-570 006, India
| | - K Ramachandra Kini
- Downy Mildew Research Laboratory, Department of Studies in Applied Botany and Biotechnology, University of Mysore, Manasagangotri Mysore-570 006, India
| | - B R Sarosh
- Downy Mildew Research Laboratory, Department of Studies in Applied Botany and Biotechnology, University of Mysore, Manasagangotri Mysore-570 006, India
| | - N P Shetty
- Section for Plant Pathology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark
| | - H S Shetty
- Downy Mildew Research Laboratory, Department of Studies in Applied Botany and Biotechnology, University of Mysore, Manasagangotri Mysore-570 006, India
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Mattinen L, Tshuikina M, Mäe A, Pirhonen M. Identification and characterization of Nip, necrosis-inducing virulence protein of Erwinia carotovora subsp. carotovora. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:1366-75. [PMID: 15597742 DOI: 10.1094/mpmi.2004.17.12.1366] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Erwinia carotovora subsp. carotovora is a gram-negative bacterium that causes soft rot disease of many cultivated crops. When a collection of E. carotovora subsp. carotovora isolates was analyzed on a Southern blot using the harpin-encoding gene hrpN as probe, several harpinless isolates were found. Regulation of virulence determinants in one of these, strain SCC3193, has been characterized extensively. It is fully virulent on potato and in Arabidopsis thaliana. An RpoS (SigmaS) mutant of SCC3193, producing elevated levels of secreted proteins, was found to cause lesions resembling the hypersensitive response when infiltrated into tobacco leaf tissue. This phenotype was evident only when bacterial cells had been cultivated on solid minimal medium at low pH and temperature. The protein causing'the cell death was purified and sequenced, and the corresponding gene was cloned. The deduced sequence of the necrosis-inducing protein (Nip) showed homology to necrosis- and ethylene-inducing elicitors of fungi and oomycetes. A mutant strain of E. carotovora subsp. carotovora lacking the nip gene showed reduced virulence in potato tuber assay but was unaffected in virulence in potato stem or on other tested host plants.
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Affiliation(s)
- Laura Mattinen
- Department of Applied Biology, FIN-00014, University of Helsinki, Finland
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Pemberton CL, Salmond GPC. The Nep1-like proteins-a growing family of microbial elicitors of plant necrosis. MOLECULAR PLANT PATHOLOGY 2004; 5:353-9. [PMID: 20565603 DOI: 10.1111/j.1364-3703.2004.00235.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
SUMMARY A novel family of microbial elicitors of plant necrosis has been identified. Designated Nep1-like proteins (NLPs), after the first family member isolated, they range from 24 to 26 kDa and are found in a variety of taxonomically unrelated micro-organisms. These include several fungi and oomycetes, as well as Gram-positive and Gram-negative bacteria. Some NLPs induce a hypersensitive-like response in plants, although the basis for initiation of this response remains unclear. Similarly, the cellular role of such highly conserved proteins is undetermined. It is not clear whether the NLPs are dedicated elicitors of plant defences or whether this induction occurs as a result of another activity.
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Affiliation(s)
- Clare L Pemberton
- Department of Biochemistry, Cambridge University, Tennis Court Road, Cambridge CB2 1QW, UK
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Nürnberger T, Brunner F, Kemmerling B, Piater L. Innate immunity in plants and animals: striking similarities and obvious differences. Immunol Rev 2004; 198:249-66. [PMID: 15199967 DOI: 10.1111/j.0105-2896.2004.0119.x] [Citation(s) in RCA: 720] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Innate immunity constitutes the first line of defense against attempted microbial invasion, and it is a well-described phenomenon in vertebrates and insects. Recent pioneering work has revealed striking similarities between the molecular organization of animal and plant systems for nonself recognition and anti-microbial defense. Like animals, plants have acquired the ability to recognize invariant pathogen-associated molecular patterns (PAMPs) that are characteristic of microbial organisms but which are not found in potential host plants. Such structures, also termed general elicitors of plant defense, are often indispensable for the microbial lifestyle and, upon receptor-mediated perception, inevitably betray the invader to the plant's surveillance system. Remarkable similarities have been uncovered in the molecular mode of PAMP perception in animals and plants, including the discovery of plant receptors resembling mammalian Toll-like receptors or cytoplasmic nucleotide-binding oligomerization domain leucine-rich repeat proteins. Moreover, molecular building blocks of PAMP-induced signaling cascades leading to the transcriptional activation of immune response genes are shared among the two kingdoms. In particular, nitric oxide as well as mitogen-activated protein kinase cascades have been implicated in triggering innate immune responses, part of which is the production of antimicrobial compounds. In addition to PAMP-mediated pathogen defense, disease resistance programs are often initiated upon plant-cultivar-specific recognition of microbial race-specific virulence factors, a recognition specificity that is not known from animals.
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Affiliation(s)
- Thorsten Nürnberger
- Institut für Pflanzenbiochemie, Abteilung Stress- und Entwicklungsbiologie, Halle/Saale, Germany.
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Tyler BM. Molecular basis of recognition between phytophthora pathogens and their hosts. ANNUAL REVIEW OF PHYTOPATHOLOGY 2002; 40:137-167. [PMID: 12147757 DOI: 10.1146/annurev.phyto.40.120601.125310] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Recognition is the earliest step in any direct plant-microbe interaction. Recognition between Phytophthora pathogens, which are oomycetes, phylogenetically distinct from fungi, has been studied at two levels. Recognition of the host by the pathogen has focused on recognition of chemical, electrical, and physical features of plant roots by zoospores. Both host-specific factors such as isoflavones, and host-nonspecific factors such as amino acids, calcium, and electrical fields, influence zoospore taxis, encystment, cyst germination, and hyphal chemotropism in guiding the pathogen to potential infection sites. Recognition of the pathogen by the host defense machinery has been analyzed using biochemical and genetic approaches. Biochemical approaches have identified chemical elicitors of host defense responses, and in some cases, their cognate receptors from the host. Some elicitors, such as glucans and fatty acids, have broad host ranges, whereas others such as elicitins have narrow host ranges. Most elicitors identified appear to contribute primarily to basic or nonhost resistance. Genetic analysis has identified host resistance (R) genes and pathogen avirulence (Avr) genes that interact in a gene-for-gene manner. One Phytophthora Avr gene, Avr1b from P. sojae, has been cloned and characterized. It encodes a secreted elicitor that triggers a system-wide defense response in soybean plants carrying the cognate R gene, Rps1b.
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Affiliation(s)
- Brett M Tyler
- Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
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