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Abdeeva IA, Maloshenok LG, Pogorelko GV, Bruskin SA. Using an RNA Aptamer to Inhibit the Action of Effector Proteins of Plant Pathogens. Int J Mol Sci 2023; 24:16604. [PMID: 38068927 PMCID: PMC10705891 DOI: 10.3390/ijms242316604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 11/10/2023] [Accepted: 11/18/2023] [Indexed: 12/18/2023] Open
Abstract
In previous work, we experimentally demonstrated the possibility of using RNA aptamers to inhibit endogenous protein expression and their function within plant cells In the current work, we show that our proposed method is suitable for inhibiting the functions of exogenous, foreign proteins delivered into the plant via various mechanisms, including pathogen proteins. Stringent experimentation produced robust RNA aptamers that are able to bind to the recombinant HopU1 effector protein of P. syringae bacteria. This research uses genetic engineering methods to constitutively express/transcribe HopU1 RNA aptamers in transgenic A. thaliana. Our findings support the hypothesis that HopU1 aptamers can actively interfere with the function of the HopU1 protein and thereby increase resistance to phytopathogens of the genus P. syringae pv. tomato DC 3000.
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Affiliation(s)
- Inna A. Abdeeva
- N.I. Vavilov Institute of General Genetics Russian Academy of Sciences, Gubkina Str. 3, 119333 Moscow, Russia (S.A.B.)
| | - Liliya G. Maloshenok
- N.I. Vavilov Institute of General Genetics Russian Academy of Sciences, Gubkina Str. 3, 119333 Moscow, Russia (S.A.B.)
| | - Gennady V. Pogorelko
- N.I. Vavilov Institute of General Genetics Russian Academy of Sciences, Gubkina Str. 3, 119333 Moscow, Russia (S.A.B.)
- Department of Plant Pathology and Microbiology, Iowa State University, Ames, IA 50011, USA
| | - Sergey A. Bruskin
- N.I. Vavilov Institute of General Genetics Russian Academy of Sciences, Gubkina Str. 3, 119333 Moscow, Russia (S.A.B.)
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2
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Bertoni G. Xanthomonas counteracts host immunity by targeting the exocyst complex. THE PLANT CELL 2022; 34:3166-3167. [PMID: 35762457 PMCID: PMC9421458 DOI: 10.1093/plcell/koac173] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 06/01/2022] [Indexed: 06/15/2023]
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3
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Wen T, Wu X, Hu L, Qiu Y, Rui L, Zhang Y, Ding X, Ye J. A novel pine wood nematode effector, BxSCD1, suppresses plant immunity and interacts with an ethylene-forming enzyme in pine. MOLECULAR PLANT PATHOLOGY 2021; 22:1399-1412. [PMID: 34396673 PMCID: PMC8518578 DOI: 10.1111/mpp.13121] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 07/27/2021] [Accepted: 07/28/2021] [Indexed: 05/13/2023]
Abstract
The plant-parasitic nematode Bursaphelenchus xylophilus, the causal agent of pine wilt disease (PWD), causes enormous economic loss every year. Currently, little is known about the pathogenic mechanisms of PWD. Several effectors have been identified in B. xylophilus, but their functions and host targets have yet to be elucidated. Here, we demonstrated that BxSCD1 suppresses cell death and inhibits B. xylophilus PAMP BxCDP1-triggered immunity in Nicotiana benthamiana and Pinus thunbergii. BxSCD1 was transcriptionally upregulated in the early stage of B. xylophilus infection. In situ hybridization experiments showed that BxSCD1 was specifically expressed in the dorsal glands and intestine. Cysteine residues are essential for the function of BxSCD1. Transient expression of BxSCD1 in N. benthamiana revealed that it was primarily targeted to the cytoplasm and nucleus. The morbidity was significantly reduced in P. thunbergii infected with B. xylophilus when BxSCD1 was silenced. We identified 1-aminocyclopropane-1-carboxylate oxidase 1, the actual ethylene-forming enzyme, as a host target of BxSCD1 by yeast two-hybrid and coimmunoprecipitation. Overall, this study illustrated that BxSCD1 played a critical role in the B. xylophilus-plant interaction.
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Affiliation(s)
- Tong‐Yue Wen
- Co‐Innovation Center for Sustainable Forestry in Southern ChinaCollege of ForestryNanjing Forestry UniversityNanjingChina
- Jiangsu Key Laboratory for Prevention and Management of Invasive SpeciesNanjing Forestry UniversityNanjingChina
| | - Xiao‐Qin Wu
- Co‐Innovation Center for Sustainable Forestry in Southern ChinaCollege of ForestryNanjing Forestry UniversityNanjingChina
- Jiangsu Key Laboratory for Prevention and Management of Invasive SpeciesNanjing Forestry UniversityNanjingChina
| | - Long‐Jiao Hu
- Co‐Innovation Center for Sustainable Forestry in Southern ChinaCollege of ForestryNanjing Forestry UniversityNanjingChina
- Jiangsu Key Laboratory for Prevention and Management of Invasive SpeciesNanjing Forestry UniversityNanjingChina
| | - Yi‐Jun Qiu
- Co‐Innovation Center for Sustainable Forestry in Southern ChinaCollege of ForestryNanjing Forestry UniversityNanjingChina
- Jiangsu Key Laboratory for Prevention and Management of Invasive SpeciesNanjing Forestry UniversityNanjingChina
| | - Lin Rui
- Co‐Innovation Center for Sustainable Forestry in Southern ChinaCollege of ForestryNanjing Forestry UniversityNanjingChina
- Jiangsu Key Laboratory for Prevention and Management of Invasive SpeciesNanjing Forestry UniversityNanjingChina
| | - Yan Zhang
- Co‐Innovation Center for Sustainable Forestry in Southern ChinaCollege of ForestryNanjing Forestry UniversityNanjingChina
- Jiangsu Key Laboratory for Prevention and Management of Invasive SpeciesNanjing Forestry UniversityNanjingChina
| | - Xiao‐Lei Ding
- Co‐Innovation Center for Sustainable Forestry in Southern ChinaCollege of ForestryNanjing Forestry UniversityNanjingChina
- Jiangsu Key Laboratory for Prevention and Management of Invasive SpeciesNanjing Forestry UniversityNanjingChina
| | - Jian‐Ren Ye
- Co‐Innovation Center for Sustainable Forestry in Southern ChinaCollege of ForestryNanjing Forestry UniversityNanjingChina
- Jiangsu Key Laboratory for Prevention and Management of Invasive SpeciesNanjing Forestry UniversityNanjingChina
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Huang G, Liu Z, Gu B, Zhao H, Jia J, Fan G, Meng Y, Du Y, Shan W. An RXLR effector secreted by Phytophthora parasitica is a virulence factor and triggers cell death in various plants. MOLECULAR PLANT PATHOLOGY 2019; 20:356-371. [PMID: 30320960 PMCID: PMC6637884 DOI: 10.1111/mpp.12760] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
RXLR effectors encoded by Phytophthora species play a central role in pathogen-plant interactions. An understanding of the biological functions of RXLR effectors is conducive to the illumination of the pathogenic mechanisms and the development of disease control strategies. However, the virulence function of Phytophthora parasitica RXLR effectors is poorly understood. Here, we describe the identification of a P. parasitica RXLR effector gene, PPTG00121 (PpE4), which is highly transcribed during the early stages of infection. Live cell imaging of P. parasitica transformants expressing a full-length PpE4 (E4FL)-mCherry protein indicated that PpE4 is secreted and accumulates around haustoria during plant infection. Silencing of PpE4 in P. parasitica resulted in significantly reduced virulence on Nicotiana benthamiana. Transient expression of PpE4 in N. benthamiana in turn restored the pathogenicity of the PpE4-silenced lines. Furthermore, the expression of PpE4 in both N. benthamiana and Arabidopsis thaliana consistently enhanced plant susceptibility to P. parasitica. These results indicate that PpE4 contributes to pathogen infection. Finally, heterologous expression experiments showed that PpE4 triggers non-specific cell death in a variety of plants, including tobacco, tomato, potato and A. thaliana. Virus-induced gene silencing assays revealed that PpE4-induced cell death is dependent on HSP90, NPK and SGT1, suggesting that PpE4 is recognized by the plant immune system. In conclusion, PpE4 is an important virulence RXLR effector of P. parasitica and recognized by a wide range of host plants.
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Affiliation(s)
- Guiyan Huang
- State Key Laboratory of Crop Stress Biology for Arid AreasNorthwest A&F UniversityYanglingShaanxi712100China
- College of Life SciencesNorthwest A&F UniversityYanglingShaanxi712100China
| | - Zhirou Liu
- State Key Laboratory of Crop Stress Biology for Arid AreasNorthwest A&F UniversityYanglingShaanxi712100China
- College of Plant ProtectionNorthwest A&F UniversityYanglingShaanxi712100China
| | - Biao Gu
- State Key Laboratory of Crop Stress Biology for Arid AreasNorthwest A&F UniversityYanglingShaanxi712100China
- College of Plant ProtectionNorthwest A&F UniversityYanglingShaanxi712100China
| | - Hong Zhao
- State Key Laboratory of Crop Stress Biology for Arid AreasNorthwest A&F UniversityYanglingShaanxi712100China
- College of Plant ProtectionNorthwest A&F UniversityYanglingShaanxi712100China
| | - Jinbu Jia
- State Key Laboratory of Crop Stress Biology for Arid AreasNorthwest A&F UniversityYanglingShaanxi712100China
- College of Plant ProtectionNorthwest A&F UniversityYanglingShaanxi712100China
- Institute of Plant and Food Science, Department of BiologySouthern University of Science and TechnologyShenzhen518055China
| | - Guangjin Fan
- State Key Laboratory of Crop Stress Biology for Arid AreasNorthwest A&F UniversityYanglingShaanxi712100China
- College of Plant ProtectionNorthwest A&F UniversityYanglingShaanxi712100China
| | - Yuling Meng
- State Key Laboratory of Crop Stress Biology for Arid AreasNorthwest A&F UniversityYanglingShaanxi712100China
- College of AgronomyNorthwest A&F UniversityYanglingShaanxi712100China
| | - Yu Du
- State Key Laboratory of Crop Stress Biology for Arid AreasNorthwest A&F UniversityYanglingShaanxi712100China
- College of HorticultureNorthwest A&F UniversityYanglingShaanxi712100China
| | - Weixing Shan
- State Key Laboratory of Crop Stress Biology for Arid AreasNorthwest A&F UniversityYanglingShaanxi712100China
- College of AgronomyNorthwest A&F UniversityYanglingShaanxi712100China
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Abstract
The interactions between fungi and plants encompass a spectrum of ecologies ranging from saprotrophy (growth on dead plant material) through pathogenesis (growth of the fungus accompanied by disease on the plant) to symbiosis (growth of the fungus with growth enhancement of the plant). We consider pathogenesis in this article and the key roles played by a range of pathogen-encoded molecules that have collectively become known as effectors.
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Jing L, Guo D, Hu W, Niu X. The prediction of a pathogenesis-related secretome of Puccinia helianthi through high-throughput transcriptome analysis. BMC Bioinformatics 2017; 18:166. [PMID: 28284182 PMCID: PMC5346188 DOI: 10.1186/s12859-017-1577-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 03/03/2017] [Indexed: 11/11/2022] Open
Abstract
Background Many plant pathogen secretory proteins are known to be elicitors or pathogenic factors,which play an important role in the host-pathogen interaction process. Bioinformatics approaches make possible the large scale prediction and analysis of secretory proteins from the Puccinia helianthi transcriptome. The internet-based software SignalP v4.1, TargetP v1.01, Big-PI predictor, TMHMM v2.0 and ProtComp v9.0 were utilized to predict the signal peptides and the signal peptide-dependent secreted proteins among the 35,286 ORFs of the P. helianthi transcriptome. Results 908 ORFs (accounting for 2.6% of the total proteins) were identified as putative secretory proteins containing signal peptides. The length of the majority of proteins ranged from 51 to 300 amino acids (aa), while the signal peptides were from 18 to 20 aa long. Signal peptidase I (SpI) cleavage sites were found in 463 of these putative secretory signal peptides. 55 proteins contained the lipoprotein signal peptide recognition site of signal peptidase II (SpII). Out of 908 secretory proteins, 581 (63.8%) have functions related to signal recognition and transduction, metabolism, transport and catabolism. Additionally, 143 putative secretory proteins were categorized into 27 functional groups based on Gene Ontology terms, including 14 groups in biological process, seven in cellular component, and six in molecular function. Gene ontology analysis of the secretory proteins revealed an enrichment of hydrolase activity. Pathway associations were established for 82 (9.0%) secretory proteins. A number of cell wall degrading enzymes and three homologous proteins specific to Phytophthora sojae effectors were also identified, which may be involved in the pathogenicity of the sunflower rust pathogen. Conclusions This investigation proposes a new approach for identifying elicitors and pathogenic factors. The eventual identification and characterization of 908 extracellularly secreted proteins will advance our understanding of the molecular mechanisms of interactions between sunflower and rust pathogen and will enhance our ability to intervene in disease states. Electronic supplementary material The online version of this article (doi:10.1186/s12859-017-1577-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lan Jing
- Department of Plant Pathology, Inner Mongolia Agricultural University, Hohhot, 010019, China.
| | - Dandan Guo
- Department of Plant Pathology, Inner Mongolia Agricultural University, Hohhot, 010019, China
| | - Wenjie Hu
- Department of Plant Pathology, Inner Mongolia Agricultural University, Hohhot, 010019, China
| | - Xiaofan Niu
- Division of Plant Sciences, University of Missouri, Columbia, MO, 65211, USA
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Bentham A, Burdett H, Anderson PA, Williams SJ, Kobe B. Animal NLRs provide structural insights into plant NLR function. ANNALS OF BOTANY 2017; 119:827-702. [PMID: 27562749 PMCID: PMC5378188 DOI: 10.1093/aob/mcw171] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 05/26/2016] [Accepted: 06/07/2016] [Indexed: 05/18/2023]
Abstract
BACKGROUND The plant immune system employs intracellular NLRs (nucleotide binding [NB], leucine-rich repeat [LRR]/nucleotide-binding oligomerization domain [NOD]-like receptors) to detect effector proteins secreted into the plant cell by potential pathogens. Activated plant NLRs trigger a range of immune responses, collectively known as the hypersensitive response (HR), which culminates in death of the infected cell. Plant NLRs show structural and functional resemblance to animal NLRs involved in inflammatory and innate immune responses. Therefore, knowledge of the activation and regulation of animal NLRs can help us understand the mechanism of action of plant NLRs, and vice versa. SCOPE This review provides an overview of the innate immune pathways in plants and animals, focusing on the available structural and biochemical information available for both plant and animal NLRs. We highlight the gap in knowledge between the animal and plant systems, in particular the lack of structural information for plant NLRs, with crystal structures only available for the N-terminal domains of plant NLRs and an integrated decoy domain, in contrast to the more complete structures available for animal NLRs. We assess the similarities and differences between plant and animal NLRs, and use the structural information on the animal NLR pair NAIP/NLRC4 to derive a plausible model for plant NLR activation. CONCLUSIONS Signalling by cooperative assembly formation (SCAF) appears to operate in most innate immunity pathways, including plant and animal NLRs. Our proposed model of plant NLR activation includes three key steps: (1) initially, the NLR exists in an inactive auto-inhibited state; (2) a combination of binding by activating elicitor and ATP leads to a structural rearrangement of the NLR; and (3) signalling occurs through cooperative assembly of the resistosome. Further studies, structural and biochemical in particular, will be required to provide additional evidence for the different features of this model and shed light on the many existing variations, e.g. helper NLRs and NLRs containing integrated decoys.
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Affiliation(s)
- Adam Bentham
- School of Biological Sciences, Flinders University, Adelaide, SA 5001, Australia
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Hayden Burdett
- School of Biological Sciences, Flinders University, Adelaide, SA 5001, Australia
| | - Peter A. Anderson
- School of Biological Sciences, Flinders University, Adelaide, SA 5001, Australia
| | - Simon J. Williams
- School of Biological Sciences, Flinders University, Adelaide, SA 5001, Australia
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Queensland 4072, Australia
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra 2601, Australia
| | - Bostjan Kobe
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Queensland 4072, Australia
- For correspondence. E-mail
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Khatabi B, Wen RH, Hajimorad MR. Fitness penalty in susceptible host is associated with virulence of Soybean mosaic virus on Rsv1-genotype soybean: a consequence of perturbation of HC-Pro and not P3. MOLECULAR PLANT PATHOLOGY 2013; 14:885-97. [PMID: 23782556 PMCID: PMC6638797 DOI: 10.1111/mpp.12054] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The multigenic Rsv1 locus in the soybean plant introduction (PI) 'PI96983' confers extreme resistance against the majority of Soybean mosaic virus (SMV) strains, including SMV-N, but not SMV-G7 and SMV-G7d. In contrast, in susceptible soybean cultivars lacking a functional Rsv1 locus, such as 'Williams82' (rsv1), SMV-N induces severe disease symptoms and accumulates to a high level, whereas both SMV-G7 and SMV-G7d induce mild symptoms and accumulate to a significantly lower level. Gain of virulence by SMV-N on Rsv1-genotype soybean requires concurrent mutations in both the helper-component proteinase (HC-Pro) and P3 cistrons. This is because of the presence of at least two resistance (R) genes, probably belonging to the nucleotide-binding leucine-rich repeat (NB-LRR) class, within the Rsv1 locus, independently mediating the recognition of HC-Pro or P3. In this study, we show that the majority of experimentally evolved mutational pathways that disrupt the avirulence functions of SMV-N on Rsv1-genotype soybean also result in mild symptoms and reduced accumulation, relative to parental SMV-N, in Williams82 (rsv1). Furthermore, the evaluation of SMV-N-derived HC-Pro and P3 chimeras, containing homologous sequences from virulent SMV-G7 or SMV-G7d strains, as well as SMV-N-derived variants containing HC-Pro or P3 point mutation(s) associated with gain of virulence, reveals a direct correlation between the perturbation of HC-Pro and a fitness penalty in Williams82 (rsv1). Collectively, these data demonstrate that gain of virulence by SMV on Rsv1-genotype soybean results in fitness loss in a previously susceptible soybean genotype, this being a consequence of mutations in HC-Pro, but not in P3.
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Affiliation(s)
- B Khatabi
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN, 37996, USA
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de León IP, Montesano M. Activation of Defense Mechanisms against Pathogens in Mosses and Flowering Plants. Int J Mol Sci 2013; 14:3178-200. [PMID: 23380962 PMCID: PMC3588038 DOI: 10.3390/ijms14023178] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 01/23/2013] [Accepted: 01/23/2013] [Indexed: 01/09/2023] Open
Abstract
During evolution, plants have developed mechanisms to cope with and adapt to different types of stress, including microbial infection. Once the stress is sensed, signaling pathways are activated, leading to the induced expression of genes with different roles in defense. Mosses (Bryophytes) are non-vascular plants that diverged from flowering plants more than 450 million years ago, allowing comparative studies of the evolution of defense-related genes and defensive metabolites produced after microbial infection. The ancestral position among land plants, the sequenced genome and the feasibility of generating targeted knock-out mutants by homologous recombination has made the moss Physcomitrella patens an attractive model to perform functional studies of plant genes involved in stress responses. This paper reviews the current knowledge of inducible defense mechanisms in P. patens and compares them to those activated in flowering plants after pathogen assault, including the reinforcement of the cell wall, ROS production, programmed cell death, activation of defense genes and synthesis of secondary metabolites and defense hormones. The knowledge generated in P. patens together with comparative studies in flowering plants will help to identify key components in plant defense responses and to design novel strategies to enhance resistance to biotic stress.
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Affiliation(s)
- Inés Ponce de León
- Departamento de Biología Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Avenida Italia 3318, CP 11600, Montevideo, Uruguay
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +598-24872605; Fax: +598-24875548
| | - Marcos Montesano
- Laboratorio de Fisiología Vegetal, Centro de Investigaciones Nucleares, Facultad de Ciencias, Mataojo 2055, CP 11400, Montevideo, Uruguay; E-Mail:
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TMV-Gate vectors: gateway compatible tobacco mosaic virus based expression vectors for functional analysis of proteins. Sci Rep 2012; 2:874. [PMID: 23166857 PMCID: PMC3500846 DOI: 10.1038/srep00874] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 10/29/2012] [Indexed: 02/08/2023] Open
Abstract
Plant viral expression vectors are advantageous for high-throughput functional characterization studies of genes due to their capability for rapid, high-level transient expression of proteins. We have constructed a series of tobacco mosaic virus (TMV) based vectors that are compatible with Gateway technology to enable rapid assembly of expression constructs and exploitation of ORFeome collections. In addition to the potential of producing recombinant protein at grams per kilogram FW of leaf tissue, these vectors facilitate either N- or C-terminal fusions to a broad series of epitope tag(s) and fluorescent proteins. We demonstrate the utility of these vectors in affinity purification, immunodetection and subcellular localisation studies. We also apply the vectors to characterize protein-protein interactions and demonstrate their utility in screening plant pathogen effectors. Given its broad utility in defining protein properties, this vector series will serve as a useful resource to expedite gene characterization efforts.
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van Damme M, Bozkurt TO, Cakir C, Schornack S, Sklenar J, Jones AME, Kamoun S. The Irish potato famine pathogen Phytophthora infestans translocates the CRN8 kinase into host plant cells. PLoS Pathog 2012; 8:e1002875. [PMID: 22927814 PMCID: PMC3426532 DOI: 10.1371/journal.ppat.1002875] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 07/10/2012] [Indexed: 11/19/2022] Open
Abstract
Phytopathogenic oomycetes, such as Phytophthora infestans, secrete an arsenal of effector proteins that modulate plant innate immunity to enable infection. We describe CRN8, a host-translocated effector of P. infestans that has kinase activity in planta. CRN8 is a modular protein of the CRN effector family. The C-terminus of CRN8 localizes to the host nucleus and triggers cell death when the protein is expressed in planta. Cell death induction by CRN8 is dependent on its localization to the plant nucleus, which requires a functional nuclear localization signal (NLS). The C-terminal sequence of CRN8 has similarity to a serine/threonine RD kinase domain. We demonstrated that CRN8 is a functional RD kinase and that its auto-phosphorylation is dependent on an intact catalytic site. Co-immunoprecipitation experiments revealed that CRN8 forms a dimer or multimer. Heterologous expression of CRN8 in planta resulted in enhanced virulence by P. infestans. In contrast, in planta expression of the dominant-negative CRN8(R469A;D470A) resulted in reduced P. infestans infection, further implicating CRN8 in virulence. Overall, our results indicate that similar to animal parasites, plant pathogens also translocate biochemically active kinase effectors inside host cells.
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Affiliation(s)
- Mireille van Damme
- The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom
- Laboratory of Phytopathology, Wageningen University, Wageningen, The Netherlands
| | - Tolga O. Bozkurt
- The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom
| | - Cahid Cakir
- United States Department of Agriculture-Agricultural Research Service, The Plant Stress and Germplasm Development Unit, Lubbock, Texas, United States of America
| | | | - Jan Sklenar
- The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom
| | | | - Sophien Kamoun
- The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom
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12
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Potnis N, Minsavage G, Smith JK, Hurlbert JC, Norman D, Rodrigues R, Stall RE, Jones JB. Avirulence proteins AvrBs7 from Xanthomonas gardneri and AvrBs1.1 from Xanthomonas euvesicatoria contribute to a novel gene-for-gene interaction in pepper. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:307-20. [PMID: 22112215 DOI: 10.1094/mpmi-08-11-0205] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A novel hypersensitive resistance (HR) in Capsicum baccatum var. pendulum against the bacterial spot of pepper pathogen, Xanthomonas gardneri, was introgressed into C. annuum cv. Early Calwonder (ECW) to create the near-isogenic line designated as ECW-70R. A corresponding avirulence gene avrBs7, in X. gardneri elicited a strong HR in ECW-70R. A homolog of avrBs7, avrBs1.1, was found in X. euvesicatoria 85-10, which showed delayed HR on ECW-70R leaves. Genetic analysis confirmed the presence of a single dominant resistance gene, Bs7, corresponding to the two avr genes. Both AvrBs7 and AvrBs1.1 share a consensus protein tyrosine phosphatase (PTP) active site domain and can dephosphorylate para-nitrophenyl phosphate. Mutation of Cys(265) to Ser in the PTP domain and subsequent loss of enzymatic activity and HR activity indicated the importance of the PTP domain in the recognition of the Avr protein by the Bs7 gene transcripts. Superpositioning of AvrBs7 and AvrBs1.1 homology models indicated variation in the geometry of the loops adjacent to the active sites. These predicted structural differences might be responsible for the differences in HR timing due to differential activation of the resistance gene. Mutating the PTP domain of AvrBs1.1 to match that of AvrBs7 failed to activate HR on ECW-70R, indicating the possibility of differential substrate specificities between AvrBs1.1 and AvrBs7.
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Affiliation(s)
- Neha Potnis
- Department of Plant Pathology, University of Florida, Gainesville, FL, USA
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13
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Wang Q, Han C, Ferreira AO, Yu X, Ye W, Tripathy S, Kale SD, Gu B, Sheng Y, Sui Y, Wang X, Zhang Z, Cheng B, Dong S, Shan W, Zheng X, Dou D, Tyler BM, Wang Y. Transcriptional programming and functional interactions within the Phytophthora sojae RXLR effector repertoire. THE PLANT CELL 2011; 23:2064-86. [PMID: 21653195 PMCID: PMC3160037 DOI: 10.1105/tpc.111.086082] [Citation(s) in RCA: 301] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 04/05/2011] [Accepted: 05/25/2011] [Indexed: 05/18/2023]
Abstract
The genome of the soybean pathogen Phytophthora sojae contains nearly 400 genes encoding candidate effector proteins carrying the host cell entry motif RXLR-dEER. Here, we report a broad survey of the transcription, variation, and functions of a large sample of the P. sojae candidate effectors. Forty-five (12%) effector genes showed high levels of polymorphism among P. sojae isolates and significant evidence for positive selection. Of 169 effectors tested, most could suppress programmed cell death triggered by BAX, effectors, and/or the PAMP INF1, while several triggered cell death themselves. Among the most strongly expressed effectors, one immediate-early class was highly expressed even prior to infection and was further induced 2- to 10-fold following infection. A second early class, including several that triggered cell death, was weakly expressed prior to infection but induced 20- to 120-fold during the first 12 h of infection. The most strongly expressed immediate-early effectors could suppress the cell death triggered by several early effectors, and most early effectors could suppress INF1-triggered cell death, suggesting the two classes of effectors may target different functional branches of the defense response. In support of this hypothesis, misexpression of key immediate-early and early effectors severely reduced the virulence of P. sojae transformants.
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Affiliation(s)
- Qunqing Wang
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Changzhi Han
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Adriana O. Ferreira
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia 24061
| | - Xiaoli Yu
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Wenwu Ye
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Sucheta Tripathy
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia 24061
| | - Shiv D. Kale
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia 24061
| | - Biao Gu
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia 24061
- College of Plant Protection and Shaanxi Key Laboratory of Molecular Biology for Agriculture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Yuting Sheng
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Yangyang Sui
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Xiaoli Wang
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Zhengguang Zhang
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Baoping Cheng
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Suomeng Dong
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Weixing Shan
- College of Plant Protection and Shaanxi Key Laboratory of Molecular Biology for Agriculture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Xiaobo Zheng
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), Nanjing 210095, China
| | - Daolong Dou
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia 24061
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), Nanjing 210095, China
| | - Brett M. Tyler
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia 24061
| | - Yuanchao Wang
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), Nanjing 210095, China
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14
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Jeong Y, Cheong H, Choi O, Kim JK, Kang Y, Kim J, Lee S, Koh S, Moon JS, Hwang I. An HrpB-dependent but type III-independent extracellular aspartic protease is a virulence factor of Ralstonia solanacearum. MOLECULAR PLANT PATHOLOGY 2011; 12:373-80. [PMID: 21453432 PMCID: PMC6640462 DOI: 10.1111/j.1364-3703.2010.00679.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The host specificity of Ralstonia solanacearum, the causal organism of bacterial wilt on many solanaceous crops, is poorly understood. To identify a gene conferring host specificity of the bacterium, SL341 (virulent to hot pepper but avirulent to potato) and SL2029 (virulent to potato but avirulent to hot pepper) were chosen as representative strains. We identified a gene, rsa1, from SL2029 that confers avirulence to SL341 in hot pepper. The rsa1 gene encoding an 11.8-kDa protein possessed the perfect consensus hrp(II) box motif upstream of the gene. Although the expression of rsa1 was activated by HrpB, a transcriptional activator for hrp gene expression, Rsa1 protein was secreted in an Hrp type III secretion-independent manner. Rsa1 exhibited weak homology with an aspartic protease, cathepsin D, and possessed protease activity. Two specific aspartic protease inhibitors, pepstatin A and diazoacetyl-d,l-norleucine methyl ester, inhibited the protease activity of Rsa1. Substitution of two aspartic acid residues with alanine at positions 54 and 59 abolished protease activity. The SL2029 rsa1 mutant was much less virulent than the wild-type strain, but did not induce disease symptoms in hot pepper. These data indicate that Rsa1 is an extracellular aspartic protease and plays an important role for the virulence of SL2029 in potato.
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Affiliation(s)
- Yeonhwa Jeong
- Department of Agricultural Biotechnology, Seoul National University, Seoul, South Korea
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15
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Mokryakov MV, Abdeev IA, Piruzyan ES, Schaad NW, Ignatov AN. Diversity of effector genes in plant pathogenic bacteria of genus Xanthomonas. Microbiology (Reading) 2010. [DOI: 10.1134/s002626171001008x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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16
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Oh SK, Young C, Lee M, Oliva R, Bozkurt TO, Cano LM, Win J, Bos JI, Liu HY, van Damme M, Morgan W, Choi D, Van der Vossen EA, Vleeshouwers VG, Kamoun S. In planta expression screens of Phytophthora infestans RXLR effectors reveal diverse phenotypes, including activation of the Solanum bulbocastanum disease resistance protein Rpi-blb2. THE PLANT CELL 2009; 21:2928-47. [PMID: 19794118 PMCID: PMC2768934 DOI: 10.1105/tpc.109.068247] [Citation(s) in RCA: 253] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Revised: 08/01/2009] [Accepted: 09/08/2009] [Indexed: 05/07/2023]
Abstract
The Irish potato famine pathogen Phytophthora infestans is predicted to secrete hundreds of effector proteins. To address the challenge of assigning biological functions to computationally predicted effector genes, we combined allele mining with high-throughput in planta expression. We developed a library of 62 infection-ready P. infestans RXLR effector clones, obtained using primer pairs corresponding to 32 genes and assigned activities to several of these genes. This approach revealed that 16 of the 62 examined effectors cause phenotypes when expressed inside plant cells. Besides the well-studied AVR3a effector, two additional effectors, PexRD8 and PexRD36(45-1), suppressed the hypersensitive cell death triggered by the elicitin INF1, another secreted protein of P. infestans. One effector, PexRD2, promoted cell death in Nicotiana benthamiana and other solanaceous plants. Finally, two families of effectors induced hypersensitive cell death specifically in the presence of the Solanum bulbocastanum late blight resistance genes Rpi-blb1 and Rpi-blb2, thereby exhibiting the activities expected for Avrblb1 and Avrblb2. The AVRblb2 family was then studied in more detail and found to be highly variable and under diversifying selection in P. infestans. Structure-function experiments indicated that a 34-amino acid region in the C-terminal half of AVRblb2 is sufficient for triggering Rpi-blb2 hypersensitivity and that a single positively selected AVRblb2 residue is critical for recognition by Rpi-blb2.
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Affiliation(s)
- Sang-Keun Oh
- Department of Plant Pathology, Ohio State University-Ohio Agricultural Research and Development Center, Wooster, Ohio 44691
- Department of Plant Sciences, College of Agriculture and Life Sciences, Seoul National University, Seoul 151-742, Korea
| | - Carolyn Young
- Department of Plant Pathology, Ohio State University-Ohio Agricultural Research and Development Center, Wooster, Ohio 44691
| | - Minkyoung Lee
- Department of Plant Pathology, Ohio State University-Ohio Agricultural Research and Development Center, Wooster, Ohio 44691
| | - Ricardo Oliva
- The Sainsbury Laboratory, Norwich NR4 7UH, United Kingdom
| | | | | | - Joe Win
- The Sainsbury Laboratory, Norwich NR4 7UH, United Kingdom
| | | | - Hsin-Yin Liu
- Department of Plant Pathology, Ohio State University-Ohio Agricultural Research and Development Center, Wooster, Ohio 44691
| | | | - William Morgan
- Department of Biology, The College of Wooster, Wooster, Ohio 44691
| | - Doil Choi
- Department of Plant Sciences, College of Agriculture and Life Sciences, Seoul National University, Seoul 151-742, Korea
| | | | | | - Sophien Kamoun
- Department of Plant Pathology, Ohio State University-Ohio Agricultural Research and Development Center, Wooster, Ohio 44691
- The Sainsbury Laboratory, Norwich NR4 7UH, United Kingdom
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17
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Engineering key components in a synthetic eukaryotic signal transduction pathway. Mol Syst Biol 2009; 5:270. [PMID: 19455134 PMCID: PMC2694678 DOI: 10.1038/msb.2009.28] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Accepted: 04/16/2009] [Indexed: 12/16/2022] Open
Abstract
Signal transduction underlies how living organisms detect and respond to stimuli. A goal of synthetic biology is to rewire natural signal transduction systems. Bacteria, yeast, and plants sense environmental aspects through conserved histidine kinase (HK) signal transduction systems. HK protein components are typically comprised of multiple, relatively modular, and conserved domains. Phosphate transfer between these components may exhibit considerable cross talk between the otherwise apparently linear pathways, thereby establishing networks that integrate multiple signals. We show that sequence conservation and cross talk can extend across kingdoms and can be exploited to produce a synthetic plant signal transduction system. In response to HK cross talk, heterologously expressed bacterial response regulators, PhoB and OmpR, translocate to the nucleus on HK activation. Using this discovery, combined with modification of PhoB (PhoB-VP64), we produced a key component of a eukaryotic synthetic signal transduction pathway. In response to exogenous cytokinin, PhoB-VP64 translocates to the nucleus, binds a synthetic PlantPho promoter, and activates gene expression. These results show that conserved-signaling components can be used across kingdoms and adapted to produce synthetic eukaryotic signal transduction pathways.
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18
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Rybak M, Minsavage GV, Stall RE, Jones JB. Identification of Xanthomonas citri ssp. citri host specificity genes in a heterologous expression host. MOLECULAR PLANT PATHOLOGY 2009; 10:249-62. [PMID: 19236573 PMCID: PMC6640320 DOI: 10.1111/j.1364-3703.2008.00528.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We provide the first conclusive evidence that Xanthomonas axonopodis pv. citri Asiatic strain (Xac-A) and, in particular, Xac-A(w), a unique citrus canker A strain isolated from Key lime in Wellington, Florida, induces a hypersensitive reaction (HR) in grapefruit leaves. Using the heterologous tomato pathogen X. perforans, as a recipient of the Xac-A(w) genomic library, we identified a 1599-bp open reading frame responsible for HR in grapefruit, but not Key lime, and designated it avrGf1. Xac-A(w)DeltaavrGf1 produced typical, although visibly reduced, citrus canker symptoms (i.e. raised pustules) in grapefruit and typical canker symptoms in Key lime. We also determined that the X. perforans transconjugant carrying an Xac-A(w) hrpG elicited HR in grapefruit and Key lime leaves, and that xopA in X. perforans was partly responsible for HR. Xac-A transconjugants carrying the X. perforans xopA were reduced in ability to grow in grapefruit leaves relative to wild-type Xac-A. The X. perforans xopA appears to be a host-limiting factor. An avrBs3 homologue, which contained 18.5 repeats and induced HR in tomato, was designated avrTaw. This gene, when expressed in a pustule-minus Xac-A(w), did not complement pustule formation; however, pthA(w), a functional pthA homologue, complemented the mutant strain to produce typical pustules in Key lime, but markedly reduced pustules in grapefruit. Both avrBs3 homologues, when expressed in a typical Xac-A strain, resulted in typical citrus canker pustules in grapefruit, indicating that neither homologue suppressed pustule size in grapefruit. Xac-A(w) contains other unidentified factors that suppress development in grapefruit.
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Affiliation(s)
- Myrian Rybak
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA
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19
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Tian D, Yin Z. Constitutive heterologous expression of avrXa27 in rice containing the R gene Xa27 confers enhanced resistance to compatible Xanthomonas oryzae strains. MOLECULAR PLANT PATHOLOGY 2009; 10:29-39. [PMID: 19161350 PMCID: PMC6640292 DOI: 10.1111/j.1364-3703.2008.00509.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The vascular pathogen Xanthomonas oryzae pv. oryzae (Xoo) and nonvascular pathogen Xanthomonas oryzae pv. oryzicola (Xoc) cause bacterial blight (BB) and bacterial leaf streak (BLS) diseases of rice, respectively. We have previously identified the avirulence gene avrXa27 from Xoo PXO99(A), which specifically induces the expression of the rice resistance gene Xa27, ultimately leading to resistance against BB disease in rice. In this study, we have generated a transgenic rice line (L24) that expresses avrXa27 constitutively under the control of the PR1 promoter, and have examined its role in the host-pathogen interaction. L24 is not more susceptible to BB, indicating that avrXa27 does not contribute to virulence. AvrXa27 retains avirulence activity in L24 and, after crossing with a line containing Xa27, progeny display phenotypic changes including inhibition of tillering, delay in flowering, stiff leaves, early leaf senescence and activation of pathogenesis-related (PR) genes. On challenge with a variety of compatible strains of Xoo and Xoc strain L8, lines with both avrXa27 and Xa27 also show enhanced resistance to bacterial infection. The induction of Xa27 and subsequent inhibition of Xoc growth in Xa27 plants are observed on inoculation with Xoc L8 harbouring avrXa27. Our results indicate that the heterologous expression of avrXa27 in rice containing Xa27 triggers R gene-specific resistance and, at the same time, confers enhanced resistance to compatible strains of Xoo and Xoc. The expression of AvrXa27 and related proteins in plants has the potential to generate broad resistance in plants.
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Affiliation(s)
- Dongsheng Tian
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore
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20
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van Poppel PMJA, Guo J, van de Vondervoort PJI, Jung MWM, Birch PRJ, Whisson SC, Govers F. The Phytophthora infestans avirulence gene Avr4 encodes an RXLR-dEER effector. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2008; 21:1460-70. [PMID: 18842095 DOI: 10.1094/mpmi-21-11-1460] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Resistance in potato against the oomycete Phytophthora infestans is conditioned by resistance (R) genes that are introgressed from wild Solanum spp. into cultivated potato. According to the gene-for-gene model, proteins encoded by R genes recognize race-specific effectors resulting in a hypersensitive response (HR). We isolated P. infestans avirulence gene PiAvr4 using a combined approach of genetic mapping, transcriptional profiling, and bacterial artificial chromosome marker landing. PiAvr4 encodes a 287-amino-acid-protein that belongs to a superfamily of effectors sharing the putative host-cell-targeting motif RXLR-dEER. Transformation of P. infestans race 4 strains with PiAvr4 resulted in transformants that were avirulent on R4 potato plants, demonstrating that PiAvr4 is responsible for eliciting R4-mediated resistance. Moreover, expression of PiAvr4 in R4 plants using PVX agroinfection and agroinfiltration showed that PiAvr4 itself is the effector that elicits HR on R4 but not r0 plants. The presence of the RXLR-dEER motif suggested intracellular recognition of PiAvr4. This was confirmed in agroinfiltration assays but not with PVX agroinfection. Because there was always recognition of PiAvr4 retaining the signal peptide, extracellular recognition cannot be excluded. Deletion of the RXLR-dEER domain neither stimulated nor prevented elicitor activity of PiAvr4. Race 4 strains have frame shift mutations in PiAvr4 that result in truncated peptides; hence, PiAvr4 is apparently not crucial for virulence.
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Affiliation(s)
- Pieter M J A van Poppel
- Laboratory of Phytopathology, Wageningen University, Binnenhaven 5, 6709 PD Wageningen and Graduate School Experimental Plant Sciences, The Netherlands
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21
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Chiba S, Miyanishi M, Andika IB, Kondo H, Tamada T. Identification of amino acids of the beet necrotic yellow vein virus p25 protein required for induction of the resistance response in leaves of Beta vulgaris plants. J Gen Virol 2008; 89:1314-1323. [PMID: 18420811 DOI: 10.1099/vir.0.83624-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The RNA3-encoded p25 protein of beet necrotic yellow vein virus (BNYVV) is responsible for the production of rhizomania symptoms of sugar beet roots (Beta vulgaris subsp. vulgaris). Here, it was found that the presence of the p25 protein is also associated with the resistance response in rub-inoculated leaves of sugar beet and wild beet (Beta vulgaris subsp. maritima) plants. The resistance phenotype displayed a range of symptoms from no visible lesions to necrotic or greyish lesions at the inoculation site, and only very low levels of virus and viral RNA accumulated. The susceptible phenotype showed large, bright yellow lesions and developed high levels of virus accumulation. In roots after Polymyxa betae vector inoculation, however, no drastic differences in virus and viral RNA accumulation levels were found between plants with susceptible and resistant phenotypes, except at an early stage of infection. There was a genotype-specific interaction between BNYVV strains and two selected wild beet lines (MR1 and MR2) and sugar beet cultivars. Sequence analysis of natural BNYVV isolates and site-directed mutagenesis of the p25 protein revealed that 3 aa residues at positions 68, 70 and 179 are important in determining the resistance phenotype, and that host-genotype specificity is controlled by single amino acid changes at position 68. The mechanism of the occurrence of resistance-breaking BNYVV strains is discussed.
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Affiliation(s)
- Soutaro Chiba
- Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
| | - Masaki Miyanishi
- Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
| | - Ida Bagus Andika
- Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
| | - Hideki Kondo
- Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
| | - Tetsuo Tamada
- Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
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22
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Dou D, Kale SD, Wang X, Chen Y, Wang Q, Wang X, Jiang RHY, Arredondo FD, Anderson RG, Thakur PB, McDowell JM, Wang Y, Tyler BM. Conserved C-terminal motifs required for avirulence and suppression of cell death by Phytophthora sojae effector Avr1b. THE PLANT CELL 2008; 20:1118-33. [PMID: 18390593 PMCID: PMC2390733 DOI: 10.1105/tpc.107.057067] [Citation(s) in RCA: 224] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2007] [Revised: 02/26/2008] [Accepted: 03/17/2008] [Indexed: 05/17/2023]
Abstract
The sequenced genomes of oomycete plant pathogens contain large superfamilies of effector proteins containing the protein translocation motif RXLR-dEER. However, the contributions of these effectors to pathogenicity remain poorly understood. Here, we show that the Phytophthora sojae effector protein Avr1b can contribute positively to virulence and can suppress programmed cell death (PCD) triggered by the mouse BAX protein in yeast, soybean (Glycine max), and Nicotiana benthamiana cells. We identify three conserved motifs (K, W, and Y) in the C terminus of the Avr1b protein and show that mutations in the conserved residues of the W and Y motifs reduce or abolish the ability of Avr1b to suppress PCD and also abolish the avirulence interaction of Avr1b with the Rps1b resistance gene in soybean. W and Y motifs are present in at least half of the identified oomycete RXLR-dEER effector candidates, and we show that three of these candidates also suppress PCD in soybean. Together, these results indicate that the W and Y motifs are critical for the interaction of Avr1b with host plant target proteins and support the hypothesis that these motifs are critical for the functions of the very large number of predicted oomycete effectors that contain them.
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Affiliation(s)
- Daolong Dou
- Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
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23
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Win J, Morgan W, Bos J, Krasileva KV, Cano LM, Chaparro-Garcia A, Ammar R, Staskawicz BJ, Kamoun S. Adaptive evolution has targeted the C-terminal domain of the RXLR effectors of plant pathogenic oomycetes. THE PLANT CELL 2007; 19:2349-69. [PMID: 17675403 PMCID: PMC2002621 DOI: 10.1105/tpc.107.051037] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2007] [Revised: 06/30/2007] [Accepted: 07/07/2007] [Indexed: 05/16/2023]
Abstract
Oomycete plant pathogens deliver effector proteins inside host cells to modulate plant defense circuitry and to enable parasitic colonization. These effectors are defined by a conserved motif, termed RXLR (for Arg, any amino acid, Leu, Arg), that is located downstream of the signal peptide and that has been implicated in host translocation. Because the phenotypes of RXLR effectors extend to plant cells, their genes are expected to be the direct target of the evolutionary forces that drive the antagonistic interplay between pathogen and host. We used the draft genome sequences of three oomycete plant pathogens, Phytophthora sojae, Phytophthora ramorum, and Hyaloperonospora parasitica, to generate genome-wide catalogs of RXLR effector genes and determine the extent to which these genes are under positive selection. These analyses revealed that the RXLR sequence is overrepresented and positionally constrained in the secretome of Phytophthora relative to other eukaryotes. The three examined plant pathogenic oomycetes carry complex and diverse sets of RXLR effector genes that have undergone relatively rapid birth and death evolution. We obtained robust evidence of positive selection in more than two-thirds of the examined paralog families of RXLR effectors. Positive selection has acted for the most part on the C-terminal region, consistent with the view that RXLR effectors are modular, with the N terminus involved in secretion and host translocation and the C-terminal domain dedicated to modulating host defenses inside plant cells.
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Affiliation(s)
- Joe Win
- Department of Plant Pathology, Ohio State University Ohio Agricultural Research and Development Center, Wooster, Ohio 44691, USA
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24
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Wang L, Tang X, He C. The bifunctional effector AvrXccC of Xanthomonas campestris pv. campestris requires plasma membrane-anchoring for host recognition. MOLECULAR PLANT PATHOLOGY 2007; 8:491-501. [PMID: 20507516 DOI: 10.1111/j.1364-3703.2007.00409.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Bacterial pathogens use type III secretion systems (TTSS) to deliver effector proteins into eukaryotic cells for pathogenesis. In bacterial-plant interactions, one effector may function as an avirulence factor to betray the pathogen to the plant surveillance system and induce the hypersensitive response (HR) in the resistant host carrying a corresponding resistance (R) gene. However, the same effector can also sustain the growth of the pathogen by acting as a virulence factor to modulate plant physiology in the susceptible host lacking the corresponding R gene. Here, we identified and characterized a bifunctional TTSS effector AvrXccC belonging to the AvrB effector family in Xanthomonas campestris pv. campestris 8004. This effector is required for full bacterial virulence in the susceptible host cabbage (Brassica oleracea) and avirulence in the resistant host mustard (Brassica napiformis L.H. Baily). Expressing avrXccC in mustard-virulent strain Xcc HRI 3849A converts its virulence to avirulence. The effector AvrXccC is anchored to the plant plasma membrane, and the N-terminal myristoylation site (amino acids 2-7: GLcaSK) is essential for its localization. In addition, the avirulence function of AvrXccC for host recognition depends on its plasma membrane localization. Promoter activity assays showed that the expression of avrXccC is hrpG/hrpX-dependent. Moreover, the secretion of AvrXccC displayed hrp-dependency and the core sequence for AvrXccC translocation was defined to the N-terminal 40 amino acids.
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Affiliation(s)
- Lifeng Wang
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, China
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25
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Nimchuk ZL, Fisher EJ, Desveaux D, Chang JH, Dangl JL. The HopX (AvrPphE) family of Pseudomonas syringae type III effectors require a catalytic triad and a novel N-terminal domain for function. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2007; 20:346-57. [PMID: 17427805 DOI: 10.1094/mpmi-20-4-0346] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Many gram-negative plant pathogenic bacteria employ type III secretion systems to deliver effector proteins directly into the host cell during infection. On susceptible hosts, type III effectors aid pathogen growth by manipulating host defense pathways. On resistant hosts, some effectors can activate specific host disease resistance (R) genes, leading to generation of rapid and effective immune responses. The biochemical basis of these processes is poorly understood. The HopX (AvrPphE) family is a widespread type III effector among phytopathogenic bacteria. We determined that HopX family members are modular proteins composed of a conserved putative cysteine-based catalytic triad and a conserved potential target/cofactor interaction domain. HopX is soluble in host cells. Putative catalytic triad residues are required for avirulence activity on resistant bean hosts and for the generation of a cell-death response in specific Arabidopsis genotypes. The putative target/cofactor interaction domain is also required for these activities. Our data suggest that specific interaction with and modification of a cytosolic host target drives HopX recognition in resistant hosts and may contribute to virulence in susceptible hosts. Surprisingly, the Legionella pneumophila genome was found to contain a protein with similarity to HopX in sequence and domain arrangement, suggesting that these proteins might also contribute to animal pathogenesis and could be delivered to plant and animal hosts by diverse secretion systems.
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Affiliation(s)
- Zachary L Nimchuk
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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26
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Webb CA, Fellers JP. Cereal rust fungi genomics and the pursuit of virulence and avirulence factors. FEMS Microbiol Lett 2006; 264:1-7. [PMID: 17020542 DOI: 10.1111/j.1574-6968.2006.00400.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Rust diseases cause significant reductions annually in yield of cereal crops worldwide. Traditional monoculture cropping systems apply significant selection pressure on the pathogen to cause rapid shifts in pathotypes. Plant breeders strive to stay ahead of the evolving pathogens by releasing new crop genotypes with new rust resistance genes or gene combinations. Owing to the limited number of known resistance genes and the lack of molecular understanding of the plant-pathogen interaction, rusts remain challenging organisms to study, both at organismal and molecular levels. This review discusses recent progress by a number of laboratories towards better understanding the molecular component of rust disease resistance.
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Affiliation(s)
- Craig A Webb
- USDA-APHIS-PPQ, Department of Plant Pathology, Manhattan, KS 66506, USA.
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27
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Zou LF, Wang XP, Xiang Y, Zhang B, Li YR, Xiao YL, Wang JS, Walmsley AR, Chen GY. Elucidation of the hrp clusters of Xanthomonas oryzae pv. oryzicola that control the hypersensitive response in nonhost tobacco and pathogenicity in susceptible host rice. Appl Environ Microbiol 2006; 72:6212-24. [PMID: 16957248 PMCID: PMC1563621 DOI: 10.1128/aem.00511-06] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2006] [Accepted: 06/09/2006] [Indexed: 01/03/2023] Open
Abstract
Xanthomonas oryzae pv. oryzicola, the cause of bacterial leaf streak in rice, possesses clusters of hrp genes that determine its ability to elicit a hypersensitive response (HR) in nonhost tobacco and pathogenicity in host rice. A 27-kb region of the genome of X. oryzae pv. oryzicola (RS105) was identified and sequenced, revealing 10 hrp, 9 hrc (hrp conserved), and 8 hpa (hrp-associated) genes and 7 regulatory plant-inducible promoter boxes. While the region from hpa2 to hpaB and the hrpF operon resembled the corresponding genes of other xanthomonads, the hpaB-hrpF region incorporated an hrpE3 gene that was not present in X. oryzae pv. oryzae. We found that an hrpF mutant had lost the ability to elicit the HR in tobacco and pathogenicity in adult rice plants but still caused water-soaking symptoms in rice seedlings and that Hpa1 is an HR elicitor in nonhost tobacco whose expression is controlled by an hrp regulator, HrpX. Using an Hrp phenotype complementation test, we identified a small hrp cluster containing the hrpG and hrpX regulatory genes, which is separated from the core hrp cluster. In addition, we identified a gene, prhA (plant-regulated hrp), that played a key role in the Hrp phenotype of X. oryzae pv. oryzicola but was neither in the core hrp cluster nor in the hrp regulatory cluster. A prhA mutant failed to reduce the HR in tobacco and pathogenicity in rice but caused water-soaking symptoms in rice. This is the first report that X. oryzae pv. oryzicola possesses three separate DNA regions for HR induction in nonhost tobacco and pathogenicity in host rice, which will provide a fundamental base to understand pathogenicity determinants of X. oryzae pv. oryzicola compared with those of X. oryzae pv. oryzae.
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Affiliation(s)
- Li-Fang Zou
- Key Laboratory of Monitoring and Management for Plant Diseases and Insects, Ministry of Agriculture, Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
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Sanabria NM, Dubery IA. Differential display profiling of the Nicotiana response to LPS reveals elements of plant basal resistance. Biochem Biophys Res Commun 2006; 344:1001-7. [PMID: 16643858 DOI: 10.1016/j.bbrc.2006.03.216] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Accepted: 03/30/2006] [Indexed: 01/03/2023]
Abstract
The identification of cDNAs, representing up-regulated genes induced by lipopolysaccharides from Burkholderia cepacia, was achieved by differential display of mRNAs isolated from tobacco cells. In addition to up-regulation of superoxide dismutase, involved in the production of the signalling and defense molecule, hydrogen peroxide; differentially expressed cDNAs, indicative of the operation of an innate immune recognition system and expression of basal resistance, were identified. These include homologs to a receptor-like protein kinase; a binding protein for the type III secreted effector protein, harpin; a virus resistance N gene; an endogenous pararetrovirus and the Pto kinase. The altered gene expression may be responsible for activation of surveillance mechanisms and enhancement of the non-self recognition capacity. The putative roles of these transcripts in LPS-induced responses are discussed in relation to emerging concepts of innate immunity.
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Affiliation(s)
- Natasha M Sanabria
- Department of Biochemistry, University of Johannesburg, Kingsway Campus, P.O. Box 524, Auckland Park 2006, South Africa
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Fujikawa T, Ishihara H, Leach JE, Tsuyumu S. Suppression of defense response in plants by the avrBs3/pthA gene family of Xanthomonas spp. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:342-9. [PMID: 16570663 DOI: 10.1094/mpmi-19-0342] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Effector genes of some plant-pathogenic bacteria, including some members of the avrBs3/pthA effector gene family from Xanthomonas spp., confer not only genotype-specific disease resistance but also pathogen aggressiveness or virulence. In addition, some effector gene products suppress induction of a nonspecific (or general) hypersensitive response (HR). To determine whether the Xanthomonas avrBs3/pthA gene family members apl1, avrXa7, or avrXa10 also confer suppressor activity, we introduced constructs with each effector gene into Pseudomonas fluorescens 55 that expressed the entire hrp cluster from P. syringae pv. syringae in cosmid pHIR11. When inoculated to tobacco 'Bright Yellow', P fluorescens (pHIR11) induces the HR and expression of four tobacco defense response genes: HIN1, RbohB, PAL, and PR1. When P. fluorescens double transformants that contained pHIR11 and constructs with apl1, avrXa7, or avrXa10 were infiltrated into tobacco, the HR and expression of three defense response genes, RbohB, PAL, and PR1, were suppressed. The suppression of the HR and defense gene expression was more efficient in the transformants with the apl1 and avrXa7 than the transformant with avrXa10. Although expression of other defense genes was suppressed by the double transformants, HIN1 expression was the same level as was observed after infiltration with P. fluorescens (pHIR11), suggesting that HIN1 may not be involved directly in HR. Taken together, our data suggest that avrXa7, avrXa10, and apl1, when delivered to plant cells by the P. syringae pv. syringae hrp secretion system, can suppress nonhost HR and associated phenotypes.
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Affiliation(s)
- Takashi Fujikawa
- Faculty of Agriculture, Shizuoka University, Shizuoka, 422-8529, Japan
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Sun W, Dunning FM, Pfund C, Weingarten R, Bent AF. Within-species flagellin polymorphism in Xanthomonas campestris pv campestris and its impact on elicitation of Arabidopsis FLAGELLIN SENSING2-dependent defenses. THE PLANT CELL 2006; 18:764-79. [PMID: 16461584 PMCID: PMC1383648 DOI: 10.1105/tpc.105.037648] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Bacterial flagellins have been portrayed as a relatively invariant pathogen-associated molecular pattern. We have found within-species, within-pathovar variation for defense-eliciting activity of flagellins among Xanthomonas campestris pv campestris (Xcc) strains. Arabidopsis thaliana FLAGELLIN SENSING2 (FLS2), a transmembrane leucine-rich repeat kinase, confers flagellin responsiveness. The flg22 region was the only Xcc flagellin region responsible for detectable elicitation of Arabidopsis defense responses. A Val-43/Asp polymorphism determined the eliciting/noneliciting nature of Xcc flagellins (structural gene fliC). Arabidopsis detected flagellins carrying Asp-43 or Asn-43 but not Val-43 or Ala-43, and it responded minimally for Glu-43. Wild-type Xcc strains carrying nonrecognized flagellin were more virulent than those carrying a recognized flagellin when infiltrated into Arabidopsis leaf mesophyll, but this correlation was misleading. Isogenic Xcc fliC gene replacement strains expressing eliciting or noneliciting flagellins grew similarly, both in leaf mesophyll and in hydathode/vascular colonization assays. The plant FLS2 genotype also had no detectable effect on disease outcome when previously untreated plants were infected by Xcc. However, resistance against Xcc was enhanced if FLS2-dependent responses were elicited 1 d before Xcc infection. Prior immunization was not required for FLS2-dependent restriction of Pseudomonas syringae pv tomato. We conclude that plant immune systems do not uniformly detect all flagellins of a particular pathogen species and that Xcc can evade Arabidopsis FLS2-mediated defenses unless the FLS2 system has been activated by previous infections.
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Affiliation(s)
- Wenxian Sun
- Department of Plant Pathology, University of Wisconsin, Madison, Wisconsin 53705, USA
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Kiba A, Sangawa Y, Ohnishi K, Yao N, Park P, Nakayashiki H, Tosa Y, Mayama S, Hikichi Y. Induction of apoptotic cell death leads to the development of bacterial rot caused by Pseudomonas cichorii. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:112-22. [PMID: 16529373 DOI: 10.1094/mpmi-19-0112] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Pseudomonas cichorii is the major causal agent of bacterial rot of lettuce. Collapse and browning symptoms were observed in lettuce leaf tissue from 15 to 24 h after inoculation (HAI) with P. cichorii; superoxide anion generation was detected at 1 to 6 HAI; and cell death was induced at 6 HAI, reaching a maximum at approximately 9 and 12 HAI. Heterochromatin condensation and DNA laddering also were observed within 3 HAI. Pharmacological studies showed that induction of cell death and DNA laddering was closely associated with de novo protein synthesis, protein kinase, intracellular reactive oxygen species, DNase, serine protease, and caspase III-like protease. Moreover, chemicals, which inhibited the induction of cell death and DNA laddering, also suppressed the development of disease symptoms. These results suggest that apoptotic cell death might be closely associated with the development of bacterial rot caused by P. cichorii.
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Affiliation(s)
- Akinori Kiba
- Laboratory of Plant Pathology and Biotechnology, Faculty of Agriculture, Kochi University, Nankoku, 783-8502 Japan.
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Meng X, Bonasera JM, Kim JF, Nissinen RM, Beer SV. Apple proteins that interact with DspA/E, a pathogenicity effector of Erwinia amylovora, the fire blight pathogen. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:53-61. [PMID: 16404953 DOI: 10.1094/mpmi-19-0053] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The disease-specific (dsp) gene dspA/E of Erwinia amylovora encodes an essential pathogenicity effector of 198 kDa, which is critical to the development of the devastating plant disease fire blight. A yeast two-hybrid assay and in vitro protein pull-down assay demonstrated that DspA/E interacts physically and specifically with four similar putative leucine-rich repeat (LRR) receptor-like serine/threonine kinases (RLK) from apple, an important host of E. amylovora. The genes encoding these four DspA/E-interacting proteins of Malus xdomestica (DIPM1 to 4) are conserved in all genera of hosts of E. amylovora tested. They also are conserved in all cultivars of apple tested that range in susceptibility to fire blight from highly susceptible to highly resistant. The four DIPMs have been characterized, and they are expressed constitutively in host plants. In silico analysis indicated that the DIPMs have similar sequence structure and resemble LRR RLKs from other organisms. Evidence is presented for direct physical interaction between DspA/E and the apple proteins encoded by the four identified clones, which may act as susceptibility factors and be essential to disease development. Knowledge of DIPMs and the interaction with DspA/E thus may facilitate understanding of fire blight development and lead to new approaches to control of disease.
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Affiliation(s)
- Xiangdong Meng
- Department of Plant Pathology, Cornell University, Ithaca, NY 14853, USA
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Abstract
The oomycetes form a phylogenetically distinct group of eukaryotic microorganisms that includes some of the most notorious pathogens of plants. Oomycetes accomplish parasitic colonization of plants by modulating host cell defenses through an array of disease effector proteins. The biology of effectors is poorly understood but tremendous progress has been made in recent years. This review classifies and catalogues the effector secretome of oomycetes. Two classes of effectors target distinct sites in the host plant: Apoplastic effectors are secreted into the plant extracellular space, and cytoplasmic effectors are translocated inside the plant cell, where they target different subcellular compartments. Considering that five species are undergoing genome sequencing and annotation, we are rapidly moving toward genome-wide catalogues of oomycete effectors. Already, it is evident that the effector secretome of pathogenic oomycetes is more complex than expected, with perhaps several hundred proteins dedicated to manipulating host cell structure and function.
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Affiliation(s)
- Sophien Kamoun
- Department of Plant Pathology, Ohio State University, Ohio Agricultural Research and Development Center, Wooster, Ohio 44691, USA.
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Büttner D, Gürlebeck D, Noël LD, Bonas U. HpaB from Xanthomonas campestris pv. vesicatoria acts as an exit control protein in type III-dependent protein secretion. Mol Microbiol 2005; 54:755-68. [PMID: 15491365 DOI: 10.1111/j.1365-2958.2004.04302.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The hrp (hypersensitive response and pathogenicity) gene cluster of the plant pathogenic bacterium Xanthomonas campestris pv. vesicatoria encodes a type III secretion (TTS) system, which injects bacterial effector proteins into the plant cell. Here, we characterized hpaB (hpa, hrp-associated), which encodes a pathogenicity factor with typical features of a TTS chaperone. We show that HpaB is important for the efficient secretion of at least five effector proteins but is dispensable for the secretion of non-effectors such as XopA and the TTS translocon protein HrpF. GST pull-down assays revealed that HpaB interacts with two unrelated effector proteins, AvrBs1 and AvrBs3, but not with XopA. The HpaB-binding site is located within the first 50 amino acids of AvrBs3. This region also contains the targeting signal for HpaB-dependent secretion, which is missing in HrpF and XopA. Intriguingly, the N-termini of HrpF and XopA target the AvrBs3Delta2 reporter for translocation in a DeltahpaB mutant but not in the wild-type strain. This indicates that HpaB plays an essential role in the exit control of the TTS system. Our data suggest that HpaB promotes the secretion of a large set of effector proteins and prevents the delivery of non-effectors into the plant cell.
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Affiliation(s)
- Daniela Büttner
- Institut für Genetik, Martin-Luther-Universität Halle-Wittenberg, D-06099 Halle (Saale), Germany
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Ting JPY, Davis BK. CATERPILLER: a novel gene family important in immunity, cell death, and diseases. Annu Rev Immunol 2005; 23:387-414. [PMID: 15771576 DOI: 10.1146/annurev.immunol.23.021704.115616] [Citation(s) in RCA: 260] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The newly discovered CATERPILLER (CLR) gene family encodes proteins with a variable but limited number of N-terminal domains, followed by a nucleotide-binding domain (NBD) and leucine-rich repeats (LRR). The N-terminal domain consists of transactivation, CARD, Pyrin, or BIR domains, with a minority containing undefined domains. These proteins are remarkably similar in structure to the TIR-NBD-LRR and CC-NBD-LRR disease resistance (R) proteins that mediate immune responses in plants. The NBD-LRR architecture is conserved in plants and vertebrates, but only remnants are found in worms and flies. The CLRs regulate inflammatory and apoptotic responses, and some act as sensors that detect pathogen products. Several CLR genes have been genetically linked to susceptibility to immunologic disorders. We describe prominent family members, including CIITA, CARD4/NOD1, NOD2/CARD15, CIAS1, CARD7/NALP1, and NAIP, in more detail. We also discuss implied roles of these proteins in diversifying immune detection and in providing a check-and-balance during inflammation.
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Affiliation(s)
- Jenny P-Y Ting
- Department of Microbiology and Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
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Oguiza JA, Asensio AC. The VirPphA/AvrPtoB family of type III effectors in Pseudomonas syringae. Res Microbiol 2005; 156:298-303. [PMID: 15808932 DOI: 10.1016/j.resmic.2004.10.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2004] [Accepted: 10/26/2004] [Indexed: 01/22/2023]
Abstract
The VirPphA/AvrPtoB family of type III effector proteins from the phytopathogenic bacterium Pseudomonas syringae is one of the models providing insights into the molecular mechanisms conferring plant disease resistance and pathogenesis. In this review we summarize recent advances concerning the VirPphA/AvrPtoB family of effectors involved in the elicitation and suppression of plant defense responses.
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Affiliation(s)
- José A Oguiza
- Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Spain.
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Ferrier-Cana E, Macadré C, Sévignac M, David P, Langin T, Geffroy V. Distinct post-transcriptional modifications result into seven alternative transcripts of the CC-NBS-LRR gene JA1tr of Phaseolus vulgaris. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2005; 110:895-905. [PMID: 15660237 DOI: 10.1007/s00122-004-1908-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2004] [Accepted: 12/09/2004] [Indexed: 05/11/2023]
Abstract
The generation of splice variants has been reported for various plant resistance (R) genes, suggesting that these variants play an important role in disease resistance. Most of the time these R genes belong to the Toll and mammalian IL-1 receptor-nucleotide-binding site-leucine-rich repeat (TIR-NBS-LRR) class of R genes. In Phaseolus vulgaris, a resistance gene cluster (referred to as the B4 R-gene cluster) has been identified at the end of linkage group B4. At this complex resistance cluster, three R specificities (Co-9, Co-y and Co-z) and two R QTLs effective against the fungal pathogen Colletotrichum lindemuthianum, the causal agent of anthracnose, have been identified. At the molecular level, four resistance gene candidates encoding putative full-length, coiled-coil (CC)-NBS-LRR R-like proteins, with LRR numbers ranging from 18 to 20, have been previously characterized. In the present study, seven cDNA corresponding to truncated R-like transcripts, belonging to the CC-NBS-LRR class of plant disease R genes, have been identified. These seven transcripts correspond to a single gene named JA1tr, which encodes, at most, only five LRRs. The seven JA1tr transcript variants result from distinct post-transcriptional modifications of JA1tr, corresponding to alternative splicing events of two introns, exon skipping and multiple 'aberrant splicing' events in the open reading frame (ORF). JA1tr was mapped at the B4 R-gene cluster identified in common bean. These post-transcriptional modifications of the single gene JA1tr could constitute an efficient source of diversity. The present results provide one of the few reports of transcript variants with truncated ORFs resulting from a CC-NBS-LRR gene.
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Affiliation(s)
- Elodie Ferrier-Cana
- Institut de Biotechnologie des Plantes, UMR-CNRS 8618, Université Paris-Sud, LPPM, bât. 630, 91405, Orsay, France
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Shah J. Lipids, lipases, and lipid-modifying enzymes in plant disease resistance. ANNUAL REVIEW OF PHYTOPATHOLOGY 2005; 43:229-60. [PMID: 16078884 DOI: 10.1146/annurev.phyto.43.040204.135951] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Lipids and lipid metabolites influence pathogenesis and resistance mechanisms associated with plant-microbe interactions. Some microorganisms sense their presence on a host by perceiving plant surface waxes, whereas others produce toxins that target plant lipid metabolism. In contrast, plants have evolved to recognize microbial lipopolysaccharides (LPSs), sphingolipids, and lipid-binding proteins as elicitors of defense response. Recent studies have demonstrated that the plasma membrane provides a surface on which some plant resistance (R) proteins perceive pathogen-derived effectors and thus confer race-specific resistance. Plant cell membranes also serve as reservoirs from which biologically active lipids and precursors of oxidized lipids are released. Some of these oxylipins, for example jasmonic acid (JA), are important signal molecules in plant defense. Arabidopsis thaliana is an excellent model plant to elucidate the biosynthesis and metabolism of lipids and lipid metabolites, and the characterization of signaling mechanisms involved in the modulation of plant defense responses by phytolipids. This review focuses on recent studies that highlight the involvement of lipids and lipid metabolites, and enzymes involved in lipid metabolism and modification in plant disease resistance.
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Affiliation(s)
- Jyoti Shah
- Division of Biology and Molecular, Cellular and Developmental Biology Program, Kansas State University, Manhattan, Kansas 66506, USA.
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Veneault-Fourrey C, Talbot NJ. Moving Toward a Systems Biology Approach to the Study of Fungal Pathogenesis in the Rice Blast Fungus Magnaporthe grisea. ADVANCES IN APPLIED MICROBIOLOGY 2005; 57:177-215. [PMID: 16002013 DOI: 10.1016/s0065-2164(05)57006-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Claire Veneault-Fourrey
- School of Biological Sciences, Washington Singer Laboratories, University of Exeter, Exeter EX4 4QG, United Kingdom
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40
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Abstract
A vast number of plant pathogens from viroids of a few hundred nucleotides to higher plants cause diseases in our crops. Their effects range from mild symptoms to catastrophes in which large areas planted to food crops are destroyed. Catastrophic plant disease exacerbates the current deficit of food supply in which at least 800 million people are inadequately fed. Plant pathogens are difficult to control because their populations are variable in time, space, and genotype. Most insidiously, they evolve, often overcoming the resistance that may have been the hard-won achievement of the plant breeder. In order to combat the losses they cause, it is necessary to define the problem and seek remedies. At the biological level, the requirements are for the speedy and accurate identification of the causal organism, accurate estimates of the severity of disease and its effect on yield, and identification of its virulence mechanisms. Disease may then be minimized by the reduction of the pathogen's inoculum, inhibition of its virulence mechanisms, and promotion of genetic diversity in the crop. Conventional plant breeding for resistance has an important role to play that can now be facilitated by marker-assisted selection. There is also a role for transgenic modification with genes that confer resistance. At the political level, there is a need to acknowledge that plant diseases threaten our food supplies and to devote adequate resources to their control.
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Affiliation(s)
- Richard N Strange
- Department of Biology, University College London, London WC1E 6BT, United Kingdom.
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Robertson AE, Wechter WP, Denny TP, Fortnum BA, Kluepfel DA. Relationship between avirulence gene (avrA) diversity in Ralstonia solanacearum and bacterial wilt incidence. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:1376-84. [PMID: 15597743 DOI: 10.1094/mpmi.2004.17.12.1376] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Bacterial wilt, caused by Ralstonia solanacearum, is a serious disease of tobacco in North and South Carolina. In contrast, the disease rarely occurs on tobacco in Georgia and Florida, although bacterial wilt is a common problem on tomato. We investigated whether this difference in disease incidence could be explained by qualitative characteristics of avirulence gene avrA in the R. solanacearum population in the southeastern United States. Sequence analysis established that wild-type avrA has a 792-bp open reading frame. Polymerase chain reaction (PCR) amplification of avrA from 139 R. solanacearum strains generated either 792-bp or approximately 960-bp DNA fragments. Strains that elicited a hypersensitive reaction (HR) on tobacco contained the 792-bp allele, and were pathogenic on tomato and avirulent on tobacco. All HR-negative strains generated a approximately 960-bp DNA fragment, and wilted both tomato and tobacco. The DNA sequence of avrA in six HR-negative strains revealed the presence of one of two putative miniature inverted-repeat transposable elements (MITEs): a 152-bp MITE between nucleotides 542 and 543, or a 170-bp MITE between nucleotides 461 and 462 or 574 and 575. Southern analysis suggested that the 170-bp MITE is unique to strains from the southeastern United States and the Caribbean. Mutated avrA alleles were present in strains from 96 and 75% of North and South Carolina sites, respectively, and only in 13 and 0% of the sites in Georgia and Florida, respectively. Introduction of the wildtype allele on a plasmid into four HR-negative strains reduced their virulence on both tobacco and tomato. Inactivation of avrA in an HR-positive, avirulent strain, resulted in a mutant that was weakly virulent on tobacco. Thus, the incidence of bacterial wilt of tobacco in the southeastern United States is partially explained by which avrA allele dominates the local R. solanacearum population.
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Affiliation(s)
- Alison E Robertson
- Department of Entomology, Soils and Plant Sciences, Clemson University, Clemson, SC 29634-0377, USA
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Abstract
Plant-associated Pseudomonas live as saprophytes and parasites on plant surfaces and inside plant tissues. Many plant-associated Pseudomonas promote plant growth by suppressing pathogenic micro-organisms, synthesizing growth-stimulating plant hormones and promoting increased plant disease resistance. Others inhibit plant growth and cause disease symptoms ranging from rot and necrosis through to developmental dystrophies such as galls. It is not easy to draw a clear distinction between pathogenic and plant growth-promoting Pseudomonas. They colonize the same ecological niches and possess similar mechanisms for plant colonization. Pathogenic, saprophytic and plant growth-promoting strains are often found within the same species, and the incidence and severity of Pseudomonas diseases are affected by environmental factors and host-specific interactions. Plants are faced with the challenge of how to recognize and exclude pathogens that pose a genuine threat, while tolerating more benign organisms. This review examines Pseudomonas from a plant perspective, focusing in particular on the question of how plants perceive and are affected by saprophytic and plant growth-promoting Pseudomonas (PGPP), in contrast to their interactions with plant pathogenic Pseudomonas. A better understanding of the molecular basis of plant-PGPP interactions and of the key differences between pathogens and PGPP will enable researchers to make more informed decisions in designing integrated disease-control strategies and in selecting, modifying and using PGPP for plant growth promotion, bioremediation and biocontrol.
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Affiliation(s)
- Gail M Preston
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
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Caldo RA, Nettleton D, Wise RP. Interaction-dependent gene expression in Mla-specified response to barley powdery mildew. THE PLANT CELL 2004; 16:2514-28. [PMID: 15319481 PMCID: PMC520949 DOI: 10.1105/tpc.104.023382] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2004] [Accepted: 06/26/2004] [Indexed: 05/19/2023]
Abstract
Plant recognition of pathogen-derived molecules influences attack and counterattack strategies that affect the outcome of host-microbe interactions. To ascertain the global framework of host gene expression during biotrophic pathogen invasion, we analyzed in parallel the mRNA abundance of 22,792 host genes throughout 36 (genotype x pathogen x time) interactions between barley (Hordeum vulgare) and Blumeria graminis f. sp hordei (Bgh), the causal agent of powdery mildew disease. A split-split-plot design was used to investigate near-isogenic barley lines with introgressed Mla6, Mla13, and Mla1 coiled-coil, nucleotide binding site, Leu-rich repeat resistance alleles challenged with Bgh isolates 5874 (AvrMla6 and AvrMla1) and K1 (AvrMla13 and AvrMla1). A linear mixed model analysis was employed to identify genes with significant differential expression (P value < 0.0001) in incompatible and compatible barley-Bgh interactions across six time points after pathogen challenge. Twenty-two host genes, of which five were of unknown function, exhibited highly similar patterns of upregulation among all incompatible and compatible interactions up to 16 h after inoculation (hai), coinciding with germination of Bgh conidiospores and formation of appressoria. By contrast, significant divergent expression was observed from 16 to 32 hai, during membrane-to-membrane contact between fungal haustoria and host epidermal cells, with notable suppression of most transcripts identified as differentially expressed in compatible interactions. These findings provide a link between the recognition of general and specific pathogen-associated molecules in gene-for-gene specified resistance and support the hypothesis that host-specific resistance evolved from the recognition and prevention of the pathogen's suppression of plant basal defense.
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Affiliation(s)
- Rico A Caldo
- Department of Plant Pathology and Center for Plant Responses to Environmental Stresses, Iowa State University, Ames, Iowa 50011-1020, USA
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Belkhadir Y, Subramaniam R, Dangl JL. Plant disease resistance protein signaling: NBS-LRR proteins and their partners. CURRENT OPINION IN PLANT BIOLOGY 2004; 7:391-9. [PMID: 15231261 DOI: 10.1016/j.pbi.2004.05.009] [Citation(s) in RCA: 228] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Most plant disease resistance (R) proteins contain a series of leucine-rich repeats (LRRs), a nucleotide-binding site (NBS), and a putative amino-terminal signaling domain. They are termed NBS-LRR proteins. The LRRs of a wide variety of proteins from many organisms serve as protein interaction platforms, and as regulatory modules of protein activation. Genetically, the LRRs of plant R proteins are determinants of response specificity, and their action can lead to plant cell death in the form of the familiar hypersensitive response (HR). A total of 149 R genes are potentially expressed in the Arabidopsis genome, and plant cells must deal with the difficult task of assembling many of the proteins encoded by these genes into functional signaling complexes. Eukaryotic cells utilize several strategies to deal with this problem. First, proteins are spatially restricted to their sub-cellular site of function, thus improving the probability that they will interact with their proper partners. Second, these interactions are architecturally organized to avoid inappropriate signaling events and to maintain the fidelity and efficiency of the response when it is initiated. Recent results provide new insights into how the signaling potential of R proteins might be created, managed and held in check until specific stimulation following infection. Nevertheless, the roles of the R protein partners in these regulatory events that have been defined to date are unclear.
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Affiliation(s)
- Youssef Belkhadir
- Department of Biology, Coker Hall, Room 108, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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Zhao B, Ardales EY, Raymundo A, Bai J, Trick HN, Leach JE, Hulbert SH. The avrRxo1 gene from the rice pathogen Xanthomonas oryzae pv. oryzicola confers a nonhost defense reaction on maize with resistance gene Rxo1. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:771-9. [PMID: 15242171 DOI: 10.1094/mpmi.2004.17.7.771] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Maize lines that contain the single dominant gene Rxo1 exhibit a rapid hypersensitive response (HR) after infiltration with the rice bacterial streak pathogen Xanthomonas oryzae pv. oryzicola, but not with the rice bacterial blight pathogen X. oryzae pv. oryzae. The avirulence effector gene that corresponds to Rxo1, designated avrRxo1, was identified in an X. oryzae pv. oryzicola genomic library. When introduced into X. oryzae pv. oryzae, clones containing avrRxo1 induced an HR on maize with Rxo1, but not on maize without Rxo1. The avrRxo1 gene is 1,266 bp long and shows no significant homology to any database sequences. When expressed in an X. oryzae pv. oryzae hrpC mutant that is deficient in the type III secretion system, avrRxo1 did not elicit the HR, indicating that the avrRxo1-Rxo1 interaction is dependent on type III secretion. Transient expression of avrRxo1 in onion cells after biolistic delivery revealed that the protein product was associated with the plasma membrane. Transient expression in maize lines carrying Rxo1 resulted in cell death, suggesting that AvrRxo1 functions from inside maize cells to elicit Rxo1-dependent pathogen recognition.
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Affiliation(s)
- Bingyu Zhao
- Department of Plant Pathology, 4024 Throckmorton Plant Sciences Center, Kansas State University, Manhattan 66506-5502, USA
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Abstract
Molecular communication between plants and potential pathogens determines the ultimate outcome of their interaction. The directed delivery of microbial molecules into and around the host cell, and the subsequent perception of these by the invaded plant tissue (or lack thereof), determines the difference between disease and disease resistance. In theory, any foreign molecule produced by an invading pathogen could act as an elicitor of the broad physiological and transcriptional re-programming indicative of a plant defense response. The diversity of elicitors recognized by plants seems to support this hypothesis. Additionally, these elicitors are often virulence factors from the pathogen recognized by the host. This recognition, though genetically as simple as a ligand-receptor interaction, may require additional host proteins that are the nominal targets of virulence factor action. Transduction of recognition probably requires regulated protein degradation and results in massive changes in cellular homeostasis, including a programmed cell death known as the hypersensitive response that indicates a successful, if perhaps over-zealous, disease resistance response.
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Affiliation(s)
- Zachary Nimchuk
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA.
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Bartsev AV, Deakin WJ, Boukli NM, McAlvin CB, Stacey G, Malnoë P, Broughton WJ, Staehelin C. NopL, an effector protein of Rhizobium sp. NGR234, thwarts activation of plant defense reactions. PLANT PHYSIOLOGY 2004; 134:871-9. [PMID: 14966249 PMCID: PMC344561 DOI: 10.1104/pp.103.031740] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2003] [Revised: 09/15/2003] [Accepted: 11/20/2003] [Indexed: 05/18/2023]
Abstract
Bacterial effector proteins delivered into eukaryotic cells via bacterial type III secretion systems are important virulence factors in plant-pathogen interactions. Type III secretion systems have been found in Rhizobium species that form symbiotic, nitrogen-fixing associations with legumes. One such bacterium, Rhizobium sp. NGR234, secretes a number of type III effectors, including nodulation outer protein L (NopL, formerly y4xL). Here, we show that expression of nopL in tobacco (Nicotiana tabacum) prevents full induction of pathogenesis-related (PR) defense proteins. Transgenic tobacco plants that express nopL and were infected with potato virus Y (necrotic strain 605) exhibited only very low levels of chitinase (class I) and beta-1,3-glucanase (classes I and III) proteins. Northern-blot analysis indicated that expression of nopL in plant cells suppresses transcription of PR genes. Treatment with ethylene counteracted the effect of NopL on chitinase (class I). Transgenic Lotus japonicus plants that expressed nopL exhibited delayed development and low chitinase levels. In vitro experiments showed that NopL is a substrate for plant protein kinases. Together, these data suggest that NopL, when delivered into the plant cell, modulates the activity of signal transduction pathways that culminate in activation of PR proteins.
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Affiliation(s)
- Alexander V Bartsev
- Laboratoire de Biologie Moléculaire des Plantes Supérieures, Sciences III, Université de Genève, 1211 Genève 4, Switzerland
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Alfano JR, Collmer A. Type III secretion system effector proteins: double agents in bacterial disease and plant defense. ANNUAL REVIEW OF PHYTOPATHOLOGY 2004; 42:385-414. [PMID: 15283671 DOI: 10.1146/annurev.phyto.42.040103.110731] [Citation(s) in RCA: 507] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Many phytopathogenic bacteria inject virulence effector proteins into plant cells via a Hrp type III secretion system (TTSS). Without the TTSS, these pathogens cannot defeat basal defenses, grow in plants, produce disease lesions in hosts, or elicit the hypersensitive response (HR) in nonhosts. Pathogen genome projects employing bioinformatic methods to identify TTSS Hrp regulon promoters and TTSS pathway targeting signals suggest that phytopathogenic Pseudomonas, Xanthomonas, and Ralstonia spp. harbor large arsenals of effectors. The Hrp TTSS employs customized cytoplasmic chaperones, conserved export components in the bacterial envelope (also used by the TTSS of animal pathogens), and a more specialized set of TTSS-secreted proteins to deliver effectors across the plant cell wall and plasma membrane. Many effectors can act as molecular double agents that betray the pathogen to plant defenses in some interactions and suppress host defenses in others. Investigations of the functions of effectors within plant cells have demonstrated the plasma membrane and nucleus as subcellular sites for several effectors, revealed some effectors to possess cysteine protease or protein tyrosine phosphatase activity, and provided new clues to the coevolution of bacterium-plant interactions.
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Affiliation(s)
- James R Alfano
- The Plant Science Initiative and the Department of Plant Pathology, University of Nebraska, Lincoln, Nebraska, 68588-0660, USA.
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Lahaye T. Illuminating the molecular basis of gene-for-gene resistance; Arabidopsis thaliana RRS1-R and its interaction with Ralstonia solanacearum popP2. TRENDS IN PLANT SCIENCE 2004; 9:1-4. [PMID: 14729210 DOI: 10.1016/j.tplants.2003.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Elucidation of the molecular basis of gene-for-gene interactions between disease-resistance (R) genes and pathogen avirulence (avr) genes has been a Holy Grail of plant pathology for the past decade. Recent studies of the R-avr interaction between RRS1-R and popP2 by Laurent Deslandes et al. provide new insights and suggest a direct physical association of the encoded proteins in support of a simplistic receptor-ligand model. However, careful consideration of the experimental findings reveals that they could also be explained by molecular linker proteins that mediate formation of a PopP2 and RRS1-R uniting complex.
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Affiliation(s)
- Thomas Lahaye
- Institute of Genetics, Martin-Luther-Universität Halle-Wittenberg, 06099 (Saale), Halle, Germany.
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Badel JL, Nomura K, Bandyopadhyay S, Shimizu R, Collmer A, He SY. Pseudomonas syringae pv. tomato DC3000 HopPtoM (CEL ORF3) is important for lesion formation but not growth in tomato and is secreted and translocated by the Hrp type III secretion system in a chaperone-dependent manner. Mol Microbiol 2003; 49:1239-51. [PMID: 12940984 DOI: 10.1046/j.1365-2958.2003.03647.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Pseudomonas syringae pv. tomato DC3000 is a pathogen of tomato and Arabidopsis that injects virulence effector proteins into host cells via a type III secretion system (TTSS). TTSS-deficient mutants have a Hrp- phenotype, that is, they cannot elicit the hypersensitive response (HR) in non-host plants or pathogenesis in host plants. Mutations in effector genes typically have weak virulence phenotypes (apparently due to redundancy), but deletion of six open reading frames (ORF) in the DC3000 conserved effector locus (CEL) reduces parasitic growth and abolishes disease symptoms without affecting function of the TTSS. The inability of the DeltaCEL mutant to cause disease symptoms in tomato was restored by a clone expressing two of the six ORF that had been deleted: CEL ORF3 (HopPtoM) and ORF4 (ShcM). A DeltahopPtoM::nptII mutant was constructed and found to grow like the wild type in tomato but to be strongly reduced in its production of necrotic lesion symptoms. HopPtoM expression in DC3000 was activated by the HrpL alternative sigma factor, and the protein was secreted by the Hrp TTSS in culture and translocated into Arabidopsis cells by the Hrp TTSS during infection. Secretion and translocation were dependent on ShcM, which was neither secreted nor translocated but, like typical TTSS chaperones, could be shown to interact with HopPtoM, its cognate effector, in yeast two-hybrid experiments. Thus, HopPtoM is a type III effector that, among known plant pathogen effectors, is unusual in making a major contribution to the elicitation of lesion symptoms but not growth in host tomato leaves.
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Affiliation(s)
- Jorge L Badel
- Department of Plant Pathology, Cornell University, Ithaca, NY 14853, USA
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