1
|
Lonjon F, Lai Y, Askari N, Aiyar N, Bundalovic-Torma C, Laflamme B, Wang PW, Desveaux D, Guttman DS. The effector-triggered immunity landscape of tomato against Pseudomonas syringae. Nat Commun 2024; 15:5102. [PMID: 38877009 PMCID: PMC11178782 DOI: 10.1038/s41467-024-49425-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 05/31/2024] [Indexed: 06/16/2024] Open
Abstract
Tomato (Solanum lycopersicum) is one of the world's most important food crops, and as such, its production needs to be protected from infectious diseases that can significantly reduce yield and quality. Here, we survey the effector-triggered immunity (ETI) landscape of tomato against the bacterial pathogen Pseudomonas syringae. We perform comprehensive ETI screens in five cultivated tomato varieties and two wild relatives, as well as an immunodiversity screen on a collection of 149 tomato varieties that includes both wild and cultivated varieties. The screens reveal a tomato ETI landscape that is more limited than what was previously found in the model plant Arabidopsis thaliana. We also demonstrate that ETI eliciting effectors can protect tomato against P. syringae infection when the effector is delivered by a non-virulent strain either prior to or simultaneously with a virulent strain. Overall, our findings provide a snapshot of the ETI landscape of tomatoes and demonstrate that ETI can be used as a biocontrol treatment to protect crop plants.
Collapse
Affiliation(s)
- Fabien Lonjon
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | - Yan Lai
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | - Nasrin Askari
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | - Niharikaa Aiyar
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | | | - Bradley Laflamme
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | - Pauline W Wang
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, ON, Canada
| | - Darrell Desveaux
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada.
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, ON, Canada.
| | - David S Guttman
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada.
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, ON, Canada.
| |
Collapse
|
2
|
Vadillo‐Dieguez A, Zeng Z, Mansfield JW, Grinberg NF, Lynn SC, Gregg A, Connell J, Harrison RJ, Jackson RW, Hulin MT. Genetic dissection of the tissue-specific roles of type III effectors and phytotoxins in the pathogenicity of Pseudomonas syringae pv. syringae to cherry. MOLECULAR PLANT PATHOLOGY 2024; 25:e13451. [PMID: 38590135 PMCID: PMC11002349 DOI: 10.1111/mpp.13451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 03/13/2024] [Accepted: 03/19/2024] [Indexed: 04/10/2024]
Abstract
When compared with other phylogroups (PGs) of the Pseudomonas syringae species complex, P. syringae pv. syringae (Pss) strains within PG2 have a reduced repertoire of type III effectors (T3Es) but produce several phytotoxins. Effectors within the cherry pathogen Pss 9644 were grouped based on their frequency in strains from Prunus as the conserved effector locus (CEL) common to most P. syringae pathogens; a core of effectors common to PG2; a set of PRUNUS effectors common to cherry pathogens; and a FLEXIBLE set of T3Es. Pss 9644 also contains gene clusters for biosynthesis of toxins syringomycin, syringopeptin and syringolin A. After confirmation of virulence gene expression, mutants with a sequential series of T3E and toxin deletions were pathogenicity tested on wood, leaves and fruits of sweet cherry (Prunus avium) and leaves of ornamental cherry (Prunus incisa). The toxins had a key role in disease development in fruits but were less important in leaves and wood. An effectorless mutant retained some pathogenicity to fruit but not wood or leaves. Striking redundancy was observed amongst effector groups. The CEL effectors have important roles during the early stages of leaf infection and possibly acted synergistically with toxins in all tissues. Deletion of separate groups of T3Es had more effect in P. incisa than in P. avium. Mixed inocula were used to complement the toxin mutations in trans and indicated that strain mixtures may be important in the field. Our results highlight the niche-specific role of toxins in P. avium tissues and the complexity of effector redundancy in the pathogen Pss 9644.
Collapse
Affiliation(s)
- Andrea Vadillo‐Dieguez
- NIABCambridgeUK
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamUK
| | | | | | | | | | | | | | - Richard J. Harrison
- NIABCambridgeUK
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamUK
- Faculty of Natural Sciences, Plant Science GroupWageningen University and ResearchWageningenNetherlands
- Present address:
Faculty of Natural Sciences, Plant Science GroupWageningen University and ResearchWageningenNetherlands
| | - Robert W. Jackson
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamUK
| | - Michelle T. Hulin
- NIABCambridgeUK
- Department of Plant Soil & Microbial SciencesMichigan State UniversityEast LansingUSA
- Present address:
Department of Plant Soil & Microbial SciencesMichigan State UniversityEast LansingUSA
| |
Collapse
|
3
|
Jayaraman J, Yoon M, Hemara LM, Bohne D, Tahir J, Chen RKY, Brendolise C, Rikkerink EHA, Templeton MD. Contrasting effector profiles between bacterial colonisers of kiwifruit reveal redundant roles converging on PTI-suppression and RIN4. THE NEW PHYTOLOGIST 2023; 238:1605-1619. [PMID: 36856342 DOI: 10.1111/nph.18848] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 02/14/2023] [Indexed: 06/18/2023]
Abstract
Testing effector knockout strains of the Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) for reduced in planta growth in their native kiwifruit host revealed a number of nonredundant effectors that contribute to Psa3 virulence. Conversely, complementation in the weak kiwifruit pathogen P. syringae pv. actinidifoliorum (Pfm) for increased growth identified redundant Psa3 effectors. Psa3 effectors hopAZ1a and HopS2b and the entire exchangeable effector locus (ΔEEL; 10 effectors) were significant contributors to bacterial colonisation of the host and were additive in their effects on virulence. Four of the EEL effectors (HopD1a, AvrB2b, HopAW1a and HopD2a) redundantly contribute to virulence through suppression of pattern-triggered immunity (PTI). Important Psa3 effectors include several redundantly required effectors early in the infection process (HopZ5a, HopH1a, AvrPto1b, AvrRpm1a and HopF1e). These largely target the plant immunity hub, RIN4. This comprehensive effector profiling revealed that Psa3 carries robust effector redundancy for a large portion of its effectors, covering a few functions critical to disease.
Collapse
Affiliation(s)
- Jay Jayaraman
- The New Zealand Institute for Plant and Food Research Ltd, Mt. Albert Research Centre, Auckland, 1025, New Zealand
| | - Minsoo Yoon
- The New Zealand Institute for Plant and Food Research Ltd, Mt. Albert Research Centre, Auckland, 1025, New Zealand
| | - Lauren M Hemara
- The New Zealand Institute for Plant and Food Research Ltd, Mt. Albert Research Centre, Auckland, 1025, New Zealand
- School of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
| | - Deborah Bohne
- The New Zealand Institute for Plant and Food Research Ltd, Mt. Albert Research Centre, Auckland, 1025, New Zealand
| | - Jibran Tahir
- The New Zealand Institute for Plant and Food Research Ltd, Mt. Albert Research Centre, Auckland, 1025, New Zealand
| | - Ronan K Y Chen
- The New Zealand Institute for Plant and Food Research Ltd, Food Industry Science Centre, Palmerston North, 4472, New Zealand
| | - Cyril Brendolise
- The New Zealand Institute for Plant and Food Research Ltd, Mt. Albert Research Centre, Auckland, 1025, New Zealand
| | - Erik H A Rikkerink
- The New Zealand Institute for Plant and Food Research Ltd, Mt. Albert Research Centre, Auckland, 1025, New Zealand
| | - Matthew D Templeton
- The New Zealand Institute for Plant and Food Research Ltd, Mt. Albert Research Centre, Auckland, 1025, New Zealand
- School of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
- Bioprotection Aotearoa, Lincoln, 7647, New Zealand
| |
Collapse
|
4
|
Antibacterial mechanism of forsythoside A against Pseudomonas syringae pv. actinidiae. Microb Pathog 2022; 173:105858. [DOI: 10.1016/j.micpath.2022.105858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 10/24/2022] [Accepted: 10/25/2022] [Indexed: 11/06/2022]
|
5
|
Correa F, Beltrán MF, Millas P, Moreno Z, Hinrichsen P, Meza P, Sagredo B. Genome Sequence Resources of Pseudomonas syringae Strains Isolated from Sweet Cherry Orchards in Chile. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2022; 35:933-937. [PMID: 36176216 DOI: 10.1094/mpmi-04-22-0092-a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Affiliation(s)
- Francisco Correa
- Instituto de Investigaciones Agropecuarias (INIA), INIA Rayentué. Avenida Salamanca s/n, Rengo, Chile
| | - M Francisca Beltrán
- Instituto de Investigaciones Agropecuarias (INIA), INIA Rayentué. Avenida Salamanca s/n, Rengo, Chile
- Programa de Doctorado en Ciencias Silvoagropecuarias y Veterinarias, Campus Sur Universidad de Chile, Santa Rosa 11315, La Pintana, Santiago, Chile
| | - Paz Millas
- Instituto de Investigaciones Agropecuarias (INIA), INIA Quilamapu. Avenida Vicente Méndez 515, Chillán, Chile
| | - Zoe Moreno
- Instituto de Investigaciones Agropecuarias (INIA), INIA Rayentué. Avenida Salamanca s/n, Rengo, Chile
| | - Patricio Hinrichsen
- Instituto de Investigaciones Agropecuarias (INIA), INIA La Platina. Avenida Santa Rosa 11610, La Pintana, Santiago, Chile
| | - Pablo Meza
- Instituto de Investigaciones Agropecuarias (INIA), INIA La Platina. Avenida Santa Rosa 11610, La Pintana, Santiago, Chile
| | - Boris Sagredo
- Instituto de Investigaciones Agropecuarias (INIA), INIA Rayentué. Avenida Salamanca s/n, Rengo, Chile
| |
Collapse
|
6
|
Michalopoulou VA, Mermigka G, Kotsaridis K, Mentzelopoulou A, Celie PHN, Moschou PN, Jones JDG, Sarris PF. The host exocyst complex is targeted by a conserved bacterial type-III effector that promotes virulence. THE PLANT CELL 2022; 34:3400-3424. [PMID: 35640532 PMCID: PMC9421483 DOI: 10.1093/plcell/koac162] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 05/23/2022] [Indexed: 05/30/2023]
Abstract
For most Gram-negative bacteria, pathogenicity largely depends on the type-III secretion system that delivers virulence effectors into eukaryotic host cells. The subcellular targets for the majority of these effectors remain unknown. Xanthomonas campestris, the causal agent of black rot disease of crucifers such as Brassica spp., radish, and turnip, delivers XopP, a highly conserved core-effector protein produced by X. campestris, which is essential for virulence. Here, we show that XopP inhibits the function of the host-plant exocyst complex by direct targeting of Exo70B, a subunit of the exocyst complex, which plays a significant role in plant immunity. XopP interferes with exocyst-dependent exocytosis and can do this without activating a plant NOD-like receptor that guards Exo70B in Arabidopsis. In this way, Xanthomonas efficiently inhibits the host's pathogen-associated molecular pattern (PAMP)-triggered immunity by blocking exocytosis of pathogenesis-related protein-1A, callose deposition, and localization of the FLAGELLIN SENSITIVE2 (FLS2) immune receptor to the plasma membrane, thus promoting successful infection. Inhibition of exocyst function without activating the related defenses represents an effective virulence strategy, indicating the ability of pathogens to adapt to host defenses by avoiding host immunity responses.
Collapse
Affiliation(s)
- Vassiliki A Michalopoulou
- Department of Biology, University of Crete, Heraklion, Crete 714 09, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete 70013, Greece
| | - Glykeria Mermigka
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete 70013, Greece
| | - Konstantinos Kotsaridis
- Department of Biology, University of Crete, Heraklion, Crete 714 09, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete 70013, Greece
| | | | - Patrick H N Celie
- Division of Biochemistry, the Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Panagiotis N Moschou
- Department of Biology, University of Crete, Heraklion, Crete 714 09, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete 70013, Greece
- Department of Plant Biology, Swedish University of Agricultural Sciences, Uppsala BioCenter, Linnean Center for Plant Biology, Uppsala S-75007, Sweden
| | | | - Panagiotis F Sarris
- Department of Biology, University of Crete, Heraklion, Crete 714 09, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete 70013, Greece
- Biosciences, University of Exeter, Exeter, UK
| |
Collapse
|
7
|
Jayaraman J, Yoon M, Applegate ER, Stroud EA, Templeton MD. AvrE1 and HopR1 from Pseudomonas syringae pv. actinidiae are additively required for full virulence on kiwifruit. MOLECULAR PLANT PATHOLOGY 2020; 21:1467-1480. [PMID: 32969167 PMCID: PMC7548996 DOI: 10.1111/mpp.12989] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 08/14/2020] [Accepted: 08/14/2020] [Indexed: 06/01/2023]
Abstract
Pseudomonas syringae pv. actinidiae ICMP 18884 biovar 3 (Psa3) produces necrotic lesions during infection of its kiwifruit host. Bacterial growth in planta and lesion formation are dependent upon a functional type III secretion system (T3S), which translocates multiple effector proteins into host cells. Associated with the T3S locus is the conserved effector locus (CEL), which has been characterized and shown to be essential for the full virulence in other P. syringae pathovars. Two effectors at the CEL, hopM1 and avrE1, as well as an avrE1-related non-CEL effector, hopR1, have been shown to be redundant in the model pathogen P. syringae pv. tomato DC3000 (Pto), a close relative of Psa. However, it is not known whether CEL-related effectors are required for Psa pathogenicity. The Psa3 allele of hopM1, and its associated chaperone, shcM, have diverged significantly from their orthologs in Pto. Furthermore, the CEL effector hopAA1-1, as well as a related non-CEL effector, hopAA1-2, have both been pseudogenized. We have shown that HopM1 does not contribute to Psa3 virulence due to a truncation in shcM, a truncation conserved in the Psa lineage, probably due to the need to evade HopM1-triggered immunity in kiwifruit. We characterized the virulence contribution of CEL and related effectors in Psa3 and found that only avrE1 and hopR1, additively, are required for in planta growth and lesion production. This is unlike the redundancy described for these effectors in Pto and indicates that these two Psa3 genes are key determinants essential for kiwifruit bacterial canker disease.
Collapse
Affiliation(s)
- Jay Jayaraman
- The New Zealand Institute for Plant and Food Research LimitedAucklandNew Zealand
- Bio‐Protection Research CentreLincolnNew Zealand
| | - Minsoo Yoon
- The New Zealand Institute for Plant and Food Research LimitedAucklandNew Zealand
| | - Emma R. Applegate
- The New Zealand Institute for Plant and Food Research LimitedAucklandNew Zealand
- School of Biological SciencesUniversity of AucklandAucklandNew Zealand
- Present address:
AgResearch Ltd., Grasslands Research CentrePalmerston NorthNew Zealand
| | - Erin A. Stroud
- The New Zealand Institute for Plant and Food Research LimitedAucklandNew Zealand
- School of Biological SciencesUniversity of AucklandAucklandNew Zealand
| | - Matthew D. Templeton
- The New Zealand Institute for Plant and Food Research LimitedAucklandNew Zealand
- Bio‐Protection Research CentreLincolnNew Zealand
- School of Biological SciencesUniversity of AucklandAucklandNew Zealand
| |
Collapse
|
8
|
Laflamme B, Dillon MM, Martel A, Almeida RND, Desveaux D, Guttman DS. The pan-genome effector-triggered immunity landscape of a host-pathogen interaction. Science 2020; 367:763-768. [PMID: 32054757 DOI: 10.1126/science.aax4079] [Citation(s) in RCA: 111] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 10/18/2019] [Accepted: 01/17/2020] [Indexed: 12/24/2022]
Abstract
Effector-triggered immunity (ETI), induced by host immune receptors in response to microbial effectors, protects plants against virulent pathogens. However, a systematic study of ETI prevalence against species-wide pathogen diversity is lacking. We constructed the Pseudomonas syringae Type III Effector Compendium (PsyTEC) to reduce the pan-genome complexity of 5127 unique effector proteins, distributed among 70 families from 494 strains, to 529 representative alleles. We screened PsyTEC on the model plant Arabidopsis thaliana and identified 59 ETI-eliciting alleles (11.2%) from 19 families (27.1%), with orthologs distributed among 96.8% of P. syringae strains. We also identified two previously undescribed host immune receptors, including CAR1, which recognizes the conserved effectors AvrE and HopAA1, and found that 94.7% of strains harbor alleles predicted to be recognized by either CAR1 or ZAR1.
Collapse
Affiliation(s)
- Bradley Laflamme
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
| | - Marcus M Dillon
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
| | - Alexandre Martel
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
| | - Renan N D Almeida
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
| | - Darrell Desveaux
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3B2, Canada.
| | - David S Guttman
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3B2, Canada. .,Center for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, ON M5S 3B2, Canada
| |
Collapse
|
9
|
Convergent gain and loss of genomic islands drive lifestyle changes in plant-associated Pseudomonas. ISME JOURNAL 2019; 13:1575-1588. [PMID: 30787396 DOI: 10.1038/s41396-019-0372-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 01/04/2019] [Accepted: 01/31/2019] [Indexed: 01/07/2023]
Abstract
Host-associated bacteria can have both beneficial and detrimental effects on host health. While some of the molecular mechanisms that determine these outcomes are known, little is known about the evolutionary histories of pathogenic or mutualistic lifestyles. Using the model plant Arabidopsis, we found that closely related strains within the Pseudomonas fluorescens species complex promote plant growth and occasionally cause disease. To elucidate the genetic basis of the transition between commensalism and pathogenesis, we developed a computational pipeline and identified genomic islands that correlate with outcomes for plant health. One island containing genes for lipopeptide biosynthesis and quorum-sensing is required for pathogenesis. Conservation of the quorum-sensing machinery in this island allows pathogenic strains to eavesdrop on quorum signals in the environment and coordinate pathogenic behavior. We found that genomic loci associated with both pathogenic and commensal lifestyles were convergently gained and lost in multiple lineages through homologous recombination, possibly constituting an early step in the differentiation of pathogenic and commensal lifestyles. Collectively this work provides novel insights into the evolution of commensal and pathogenic lifestyles within a single clade of host-associated bacteria.
Collapse
|
10
|
Identifying Pseudomonas syringae Type III Secreted Effector Function via a Yeast Genomic Screen. G3-GENES GENOMES GENETICS 2019; 9:535-547. [PMID: 30573466 PMCID: PMC6385969 DOI: 10.1534/g3.118.200877] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Gram-negative bacterial pathogens inject type III secreted effectors (T3SEs) directly into host cells to promote pathogen fitness by manipulating host cellular processes. Despite their crucial role in promoting virulence, relatively few T3SEs have well-characterized enzymatic activities or host targets. This is in part due to functional redundancy within pathogen T3SE repertoires as well as the promiscuity of individual T3SEs that can have multiple host targets. To overcome these challenges, we generated and characterized a collection of yeast strains stably expressing 75 T3SE constructs from the plant pathogen Pseudomonas syringae. This collection is devised to facilitate heterologous genetic screens in yeast, a non-host organism, to identify T3SEs that target conserved eukaryotic processes. Among 75 T3SEs tested, we identified 16 that inhibited yeast growth on rich media and eight that inhibited growth on stress-inducing media. We utilized Pathogenic Genetic Array (PGA) screens to identify potential host targets of P. syringae T3SEs. We focused on the acetyltransferase, HopZ1a, which interacts with plant tubulin and alters microtubule networks. To uncover putative HopZ1a host targets, we identified yeast genes with genetic interaction profiles most similar (i.e., congruent) to the PGA profile of HopZ1a and performed a functional enrichment analysis of these HopZ1a-congruent genes. We compared the congruence analyses above to previously described HopZ physical interaction datasets and identified kinesins as potential HopZ1a targets. Finally, we demonstrated that HopZ1a can target kinesins by acetylating the plant kinesins HINKEL and MKRP1, illustrating the utility of our T3SE-expressing yeast library to characterize T3SE functions.
Collapse
|
11
|
Puigvert M, Solé M, López‐Garcia B, Coll NS, Beattie KD, Davis RA, Elofsson M, Valls M. Type III secretion inhibitors for the management of bacterial plant diseases. MOLECULAR PLANT PATHOLOGY 2019; 20:20-32. [PMID: 30062690 PMCID: PMC6430469 DOI: 10.1111/mpp.12736] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The identification of chemical compounds that prevent and combat bacterial diseases is fundamental for crop production. Bacterial virulence inhibitors are a promising alternative to classical control treatments, because they have a low environmental impact and are less likely to generate bacterial resistance. The major virulence determinant of most animal and plant bacterial pathogens is the type III secretion system (T3SS). In this work, we screened nine plant extracts and 12 isolated compounds-including molecules effective against human pathogens-for their capacity to inhibit the T3SS of plant pathogens and for their applicability as virulence inhibitors for crop protection. The screen was performed using a luminescent reporter system developed in the model pathogenic bacterium Ralstonia solanacearum. Five synthetic molecules, one natural product and two plant extracts were found to down-regulate T3SS transcription, most through the inhibition of the regulator hrpB. In addition, for three of the molecules, corresponding to salicylidene acylhydrazide derivatives, the inhibitory effect caused a dramatic decrease in the secretion capacity, which was translated into impaired plant responses. These candidate virulence inhibitors were then tested for their ability to protect plants. We demonstrated that salicylidene acylhydrazides can limit R. solanacearum multiplication in planta and protect tomato plants from bacterial speck caused by Pseudomonas syringae pv. tomato. Our work validates the efficiency of transcription reporters to discover compounds or natural product extracts that can be potentially applied to prevent bacterial plant diseases.
Collapse
Affiliation(s)
- Marina Puigvert
- Department of GeneticsUniversity of BarcelonaBarcelona08028CataloniaSpain
- Centre for Research in Agricultural Genomics (CSIC‐IRTA‐UAB‐UB)Bellaterra08193CataloniaSpain
| | - Montserrat Solé
- Centre for Research in Agricultural Genomics (CSIC‐IRTA‐UAB‐UB)Bellaterra08193CataloniaSpain
| | - Belén López‐Garcia
- Centre for Research in Agricultural Genomics (CSIC‐IRTA‐UAB‐UB)Bellaterra08193CataloniaSpain
| | - Núria S. Coll
- Centre for Research in Agricultural Genomics (CSIC‐IRTA‐UAB‐UB)Bellaterra08193CataloniaSpain
| | - Karren D. Beattie
- Griffith Institute for Drug DiscoveryGriffith UniversityQld4111Australia
| | - Rohan A. Davis
- Griffith Institute for Drug DiscoveryGriffith UniversityQld4111Australia
| | | | - Marc Valls
- Department of GeneticsUniversity of BarcelonaBarcelona08028CataloniaSpain
- Centre for Research in Agricultural Genomics (CSIC‐IRTA‐UAB‐UB)Bellaterra08193CataloniaSpain
| |
Collapse
|
12
|
Wei H, Collmer A. Defining essential processes in plant pathogenesis with Pseudomonas syringae pv. tomato DC3000 disarmed polymutants and a subset of key type III effectors. MOLECULAR PLANT PATHOLOGY 2018; 19:1779-1794. [PMID: 29277959 PMCID: PMC6638048 DOI: 10.1111/mpp.12655] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 11/10/2017] [Accepted: 12/20/2017] [Indexed: 05/22/2023]
Abstract
Pseudomonas syringae pv. tomato DC3000 and its derivatives cause disease in tomato, Arabidopsis and Nicotiana benthamiana. The primary virulence factors include a repertoire of 29 effector proteins injected into plant cells by the type III secretion system and the phytotoxin coronatine. The complete repertoire of effector genes and key coronatine biosynthesis genes have been progressively deleted and minimally reassembled to reconstitute basic pathogenic ability in N. benthamiana, and in Arabidopsis plants that have mutations in target genes that mimic effector actions. This approach and molecular studies of effector activities and plant immune system targets have highlighted a small subset of effectors that contribute to essential processes in pathogenesis. Most notably, HopM1 and AvrE1 redundantly promote an aqueous apoplastic environment, and AvrPtoB and AvrPto redundantly block early immune responses, two conditions that are sufficient for substantial bacterial growth in planta. In addition, disarmed DC3000 polymutants have been used to identify the individual effectors responsible for specific activities of the complete repertoire and to more effectively study effector domains, effector interplay and effector actions on host targets. Such work has revealed that AvrPtoB suppresses cell death elicitation in N. benthamiana that is triggered by another effector in the DC3000 repertoire, highlighting an important aspect of effector interplay in native repertoires. Disarmed DC3000 polymutants support the natural delivery of test effectors and infection readouts that more accurately reveal effector functions in key pathogenesis processes, and enable the identification of effectors with similar activities from a broad range of other pathogens that also defeat plants with cytoplasmic effectors.
Collapse
Affiliation(s)
- Hai‐Lei Wei
- School of Integrative Plant ScienceSection of Plant Pathology and Plant–Microbe Biology, Cornell UniversityIthacaNY14853USA
- Key Laboratory of Microbial Resources Collection and Preservation, Ministry of AgricultureInstitute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural SciencesBeijing100081China
| | - Alan Collmer
- School of Integrative Plant ScienceSection of Plant Pathology and Plant–Microbe Biology, Cornell UniversityIthacaNY14853USA
| |
Collapse
|
13
|
Chakravarthy S, Worley JN, Montes‐Rodriguez A, Collmer A. Pseudomonas syringae pv. tomato DC3000 polymutants deploying coronatine and two type III effectors produce quantifiable chlorotic spots from individual bacterial colonies in Nicotiana benthamiana leaves. MOLECULAR PLANT PATHOLOGY 2018; 19:935-947. [PMID: 28677296 PMCID: PMC6637995 DOI: 10.1111/mpp.12579] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 06/06/2017] [Accepted: 06/30/2017] [Indexed: 05/24/2023]
Abstract
Primary virulence factors of Pseudomonas syringae pv. tomato DC3000 include the phytotoxin coronatine (COR) and a repertoire of 29 effector proteins injected into plant cells by the type III secretion system (T3SS). DC3000 derivatives differentially producing COR, the T3SS machinery and subsets of key effectors were constructed and assayed in leaves of Nicotiana benthamiana. Bacteria were inoculated by the dipping of whole plants and assayed for population growth and the production of chlorotic spots on leaves. The strains fell into three classes. Class I strains are T3SS+ but functionally effectorless, grow poorly in planta and produce faint chlorotic spots only if COR+ . Class II strains are T3SS- or, if T3SS+ , also produce effectors AvrPtoB and HopM1. Class II strains grow better than class I strains in planta and, if COR+ , produce robust chlorotic spots. Class III strains are T3SS+ and minimally produce AvrPtoB, HopM1 and three other effectors encoded in the P. syringae conserved effector locus. These strains differ from class II strains in growing better in planta, and produce chlorotic spots without COR if the precursor coronafacic acid is produced. Assays for chlorotic spot formation, in conjunction with pressure infiltration of low-level inoculum and confocal microscopy of fluorescent protein-labelled bacteria, revealed that single bacteria in the apoplast are capable of producing colonies and associated leaf spots in a 1 : 1 : 1 manner. However, COR makes no significant contribution to the bacterial colonization of the apoplast, but, instead, enables a gratuitous, semi-quantitative, surface indicator of bacterial growth, which is determined by the strain's effector composition.
Collapse
Affiliation(s)
- Suma Chakravarthy
- School of Integrative Plant Science, Section of Plant Pathology and Plant‐Microbe BiologyCornell UniversityIthacaNY 14853USA
- Present address:
University of Maryland and Food and Drug Administration Joint Institute for Food Safety and Applied NutritionCollege ParkMD 20742USA
| | - Jay N. Worley
- School of Integrative Plant Science, Section of Plant Pathology and Plant‐Microbe BiologyCornell UniversityIthacaNY 14853USA
- Present address:
United States Department of Agriculture, Animal and Plant Health Inspection Service, Section of Biotechnology Regulatory ServicesRiverdaleMD 20737USA
| | - Adriana Montes‐Rodriguez
- School of Integrative Plant Science, Section of Plant Pathology and Plant‐Microbe BiologyCornell UniversityIthacaNY 14853USA
- Present address:
Department of Cell BiologyFriedrich‐Alexander University of Erlangen‐NurembergBavariaGermany
| | - Alan Collmer
- School of Integrative Plant Science, Section of Plant Pathology and Plant‐Microbe BiologyCornell UniversityIthacaNY 14853USA
| |
Collapse
|
14
|
Abstract
Pseudomonas syringae is one of the best-studied plant pathogens and serves as a model for understanding host-microorganism interactions, bacterial virulence mechanisms and host adaptation of pathogens as well as microbial evolution, ecology and epidemiology. Comparative genomic studies have identified key genomic features that contribute to P. syringae virulence. P. syringae has evolved two main virulence strategies: suppression of host immunity and creation of an aqueous apoplast to form its niche in the phyllosphere. In addition, external environmental conditions such as humidity profoundly influence infection. P. syringae may serve as an excellent model to understand virulence and also of how pathogenic microorganisms integrate environmental conditions and plant microbiota to become ecologically robust and diverse pathogens of the plant kingdom.
Collapse
|
15
|
Ca 2+-Induced Two-Component System CvsSR Regulates the Type III Secretion System and the Extracytoplasmic Function Sigma Factor AlgU in Pseudomonas syringae pv. tomato DC3000. J Bacteriol 2018; 200:JB.00538-17. [PMID: 29263098 DOI: 10.1128/jb.00538-17] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 12/12/2017] [Indexed: 11/20/2022] Open
Abstract
Two-component systems (TCSs) of bacteria regulate many different aspects of the bacterial life cycle, including pathogenesis. Most TCSs remain uncharacterized, with no information about the signal(s) or regulatory targets and/or role in bacterial pathogenesis. Here, we characterized a TCS in the plant-pathogenic bacterium Pseudomonas syringae pv. tomato DC3000 composed of the histidine kinase CvsS and the response regulator CvsR. CvsSR is necessary for virulence of P. syringae pv. tomato DC3000, since ΔcvsS and ΔcvsR strains produced fewer symptoms than the wild type (WT) and demonstrated reduced growth on multiple hosts. We discovered that expression of cvsSR is induced by Ca2+ concentrations found in leaf apoplastic fluid. Thus, Ca2+ can be added to the list of signals that promote pathogenesis of P. syringae pv. tomato DC3000 during host colonization. Through chromatin immunoprecipitation followed by next-generation sequencing (ChIP-seq) and global transcriptome analysis (RNA-seq), we discerned the CvsR regulon. CvsR directly activated expression of the type III secretion system regulators, hrpR and hrpS, that regulate P. syringae pv. tomato DC3000 virulence in a type III secretion system-dependent manner. CvsR also indirectly repressed transcription of the extracytoplasmic sigma factor algU and production of alginate. Phenotypic analysis determined that CvsSR inversely regulated biofilm formation, swarming motility, and cellulose production in a Ca2+-dependent manner. Overall, our results show that CvsSR is a key regulatory hub critical for interaction with host plants.IMPORTANCE Pathogenic bacteria must be able to react and respond to the surrounding environment, make use of available resources, and avert or counter host immune responses. Often, these abilities rely on two-component systems (TCSs) composed of interacting proteins that modulate gene expression. We identified a TCS in the plant-pathogenic bacterium Pseudomonas syringae that responds to the presence of calcium, which is an important signal during the plant defense response. We showed that when P. syringae is grown in the presence of calcium, this TCS regulates expression of factors contributing to disease. Overall, our results provide a better understanding of how bacterial pathogens respond to plant signals and control systems necessary for eliciting disease.
Collapse
|
16
|
Butcher BG, Chakravarthy S, D'Amico K, Stoos KB, Filiatrault MJ. Disruption of the carA gene in Pseudomonas syringae results in reduced fitness and alters motility. BMC Microbiol 2016; 16:194. [PMID: 27558694 PMCID: PMC4997734 DOI: 10.1186/s12866-016-0819-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 08/19/2016] [Indexed: 02/05/2023] Open
Abstract
Background Pseudomonas syringae infects diverse plant species and is widely used in the study of effector function and the molecular basis of disease. Although the relationship between bacterial metabolism, nutrient acquisition and virulence has attracted increasing attention in bacterial pathology, there is limited knowledge regarding these studies in Pseudomonas syringae. The aim of this study was to investigate the function of the carA gene and the small RNA P32, and characterize the regulation of these transcripts. Results Disruption of the carA gene (ΔcarA) which encodes the predicted small chain of carbamoylphosphate synthetase, resulted in arginine and pyrimidine auxotrophy in Pseudomonas syringae pv. tomato DC3000. Complementation with the wild type carA gene was able to restore growth to wild-type levels in minimal medium. Deletion of the small RNA P32, which resides immediately upstream of carA, did not result in arginine or pyrimidine auxotrophy. The expression of carA was influenced by the concentrations of both arginine and uracil in the medium. When tested for pathogenicity, ΔcarA showed reduced fitness in tomato as well as Arabidopsis when compared to the wild-type strain. In contrast, mutation of the region encoding P32 had minimal effect in planta. ΔcarA also exhibited reduced motility and increased biofilm formation, whereas disruption of P32 had no impact on motility or biofilm formation. Conclusions Our data show that carA plays an important role in providing arginine and uracil for growth of the bacteria and also influences other factors that are potentially important for growth and survival during infection. Although we find that the small RNA P32 and carA are co-transcribed, P32 does not play a role in the phenotypes that carA is required for, such as motility, cell attachment, and virulence. Additionally, our data suggests that pyrimidines may be limited in the apoplastic space of the plant host tomato. Electronic supplementary material The online version of this article (doi:10.1186/s12866-016-0819-z) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Bronwyn G Butcher
- School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY, USA.,Present Address: Cornell Lab of Ornithology, Cornell University, 159 Sapsucker Woods Rd, Ithaca, NY, USA
| | - Suma Chakravarthy
- School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY, USA
| | - Katherine D'Amico
- School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY, USA.,Emerging Pests and Pathogens Research Unit, Robert W. Holley Center for Agriculture and Health, Agricultural Research Service, United States Department of Agriculture, Ithaca, NY, USA
| | - Kari Brossard Stoos
- Department of Health Promotion and Physical Education, School of Health Sciences and Human Performance, Ithaca College, Ithaca, NY, USA
| | - Melanie J Filiatrault
- School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY, USA. .,Emerging Pests and Pathogens Research Unit, Robert W. Holley Center for Agriculture and Health, Agricultural Research Service, United States Department of Agriculture, Ithaca, NY, USA.
| |
Collapse
|
17
|
Popa C, Coll NS, Valls M, Sessa G. Yeast as a Heterologous Model System to Uncover Type III Effector Function. PLoS Pathog 2016; 12:e1005360. [PMID: 26914889 PMCID: PMC4767418 DOI: 10.1371/journal.ppat.1005360] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Type III effectors (T3E) are key virulence proteins that are injected by bacterial pathogens inside the cells of their host to subvert cellular processes and contribute to disease. The budding yeast Saccharomyces cerevisiae represents an important heterologous system for the functional characterisation of T3E proteins in a eukaryotic environment. Importantly, yeast contains eukaryotic processes with low redundancy and are devoid of immunity mechanisms that counteract T3Es and mask their function. Expression in yeast of effectors from both plant and animal pathogens that perturb conserved cellular processes often resulted in robust phenotypes that were exploited to elucidate effector functions, biochemical properties, and host targets. The genetic tractability of yeast and its amenability for high-throughput functional studies contributed to the success of this system that, in recent years, has been used to study over 100 effectors. Here, we provide a critical view on this body of work and describe advantages and limitations inherent to the use of yeast in T3E research. “Favourite” targets of T3Es in yeast are cytoskeleton components and small GTPases of the Rho family. We describe how mitogen-activated protein kinase (MAPK) signalling, vesicle trafficking, membrane structures, and programmed cell death are also often altered by T3Es in yeast and how this reflects their function in the natural host. We describe how effector structure–function studies and analysis of candidate targeted processes or pathways can be carried out in yeast. We critically analyse technologies that have been used in yeast to assign biochemical functions to T3Es, including transcriptomics and proteomics, as well as suppressor, gain-of-function, or synthetic lethality screens. We also describe how yeast can be used to select for molecules that block T3E function in search of new antibacterial drugs with medical applications. Finally, we provide our opinion on the limitations of S. cerevisiae as a model system and its most promising future applications.
Collapse
Affiliation(s)
- Crina Popa
- Genetics Department, Universitat de Barcelona, Barcelona, Catalonia, Spain
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Núria S. Coll
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Marc Valls
- Genetics Department, Universitat de Barcelona, Barcelona, Catalonia, Spain
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
- * E-mail: (GS); (MV)
| | - Guido Sessa
- Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv, Israel
- * E-mail: (GS); (MV)
| |
Collapse
|
18
|
Dudnik A, Dudler R. Virulence determinants of Pseudomonas syringae strains isolated from grasses in the context of a small type III effector repertoire. BMC Microbiol 2014; 14:304. [PMID: 25472590 PMCID: PMC4262972 DOI: 10.1186/s12866-014-0304-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 11/20/2014] [Indexed: 11/10/2022] Open
Abstract
Background Pseudomonas syringae is pathogenic to a large number of plant species. For host colonization and disease progression, strains of this bacterium utilize an array of type III-secreted effectors and other virulence factors, including small secreted molecules such as syringolin A, a peptide derivative that inhibits the eukaryotic proteasome. In strains colonizing dicotyledonous plants, the compound was demonstrated to suppress the salicylic-acid-dependent defense pathway. Here, we analyze virulence factors of three strains colonizing wheat (Triticum aestivum): P. syringae pathovar syringae (Psy) strains B64 and SM, as well as P. syringae BRIP34876. These strains have a relatively small repertoire of only seven to eleven type III secreted effectors (T3Es) and differ in their capacity to produce syringolin A. The aim of this study was to analyze the contribution of various known virulence factors in the context of a small T3E repertoire. Results We demonstrate that syringolin A production enhances disease symptom development upon direct infiltration of strains into wheat leaves. However, it is not universally required for colonization, as Psy SM, which lacks syringolin biosynthesis genes, reaches cell densities comparable to syringolin A producer P. syringae BRIP34876. Next, we show that despite the small set of T3E-encoding genes, the type III secretion system remains the key pathogenicity determinant in these strains, and that phenotypic effects of deleting T3E-coding genes become apparent only when multiple effectors are removed. Conclusions Whereas production of syringolin A is not required for successful colonization of wheat leaves by P. syringae strains, its production results in increased lesion formation. Despite the small number of known T3Es encoded by the analyzed strains, the type III secretion system is essential for endophytic growth of these strains. Electronic supplementary material The online version of this article (doi:10.1186/s12866-014-0304-5) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Alexey Dudnik
- Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, Zurich, 8008, Switzerland. .,Present address: Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kogle Allé 4, Hørsholm, 2970, Denmark.
| | - Robert Dudler
- Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, Zurich, 8008, Switzerland.
| |
Collapse
|
19
|
Matas IM, Castañeda-Ojeda MP, Aragón IM, Antúnez-Lamas M, Murillo J, Rodríguez-Palenzuela P, López-Solanilla E, Ramos C. Translocation and functional analysis of Pseudomonas savastanoi pv. savastanoi NCPPB 3335 type III secretion system effectors reveals two novel effector families of the Pseudomonas syringae complex. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2014; 27:424-36. [PMID: 24329173 DOI: 10.1094/mpmi-07-13-0206-r] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Pseudomonas savastanoi pv. savastanoi NCPPB 3335 causes olive knot disease and is a model pathogen for exploring bacterial infection of woody hosts. The type III secretion system (T3SS) effector repertoire of this strain includes 31 effector candidates plus two novel candidates identified in this study which have not been reported to translocate into plant cells. In this work, we demonstrate the delivery of seven NCPPB 3335 effectors into Nicotiana tabacum leaves, including three proteins from two novel families of the P. syringae complex effector super-repertoire (HopBK and HopBL), one of which comprises two proteins (HopBL1 and HopBL2) that harbor a SUMO protease domain. When delivered by P. fluorescens heterologously expressing a P. syringae T3SS, all seven effectors were found to suppress the production of defense-associated reactive oxygen species. Moreover, six of these effectors, including the truncated versions of HopAA1 and HopAZ1 encoded by NCPPB 3335, suppressed callose deposition. The expression of HopAZ1 and HopBL1 by functionally effectorless P. syringae pv. tomato DC3000D28E inhibited the hypersensitive response in tobacco and, additionally, expression of HopBL2 by this strain significantly increased its competitiveness in N. benthamiana. DNA sequences encoding HopBL1 and HopBL2 were uniquely detected in a collection of 31 P. savastanoi pv. savastanoi strains and other P. syringae strains isolated from woody hosts, suggesting a relevant role of these two effectors in bacterial interactions with olive and other woody plants.
Collapse
|
20
|
Moriconi V, Sellaro R, Ayub N, Soto G, Rugnone M, Shah R, Pathak GP, Gärtner W, Casal JJ. LOV-domain photoreceptor, encoded in a genomic island, attenuates the virulence of Pseudomonas syringae in light-exposed Arabidopsis leaves. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 76:322-331. [PMID: 23865633 DOI: 10.1111/tpj.12289] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 07/10/2013] [Accepted: 07/16/2013] [Indexed: 06/02/2023]
Abstract
In Arabidopsis thaliana, light signals modulate the defences against bacteria. Here we show that light perceived by the LOV domain-regulated two-component system (Pst-Lov) of Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) modulates virulence against A. thaliana. Bioinformatic analysis and the existence of an episomal circular intermediate indicate that the locus encoding Pst-Lov is present in an active genomic island acquired by horizontal transfer. Strains mutated at Pst-Lov showed enhanced growth on minimal medium and in leaves of A. thaliana exposed to light, but not in leaves incubated in darkness or buried in the soil. Pst-Lov repressed the expression of principal and alternative sigma factor genes and their downstream targets linked to bacterial growth, virulence and quorum sensing, in a strictly light-dependent manner. We propose that the function of Pst-Lov is to distinguish between soil (dark) and leaf (light) environments, attenuating the damage caused to host tissues while releasing growth out of the host. Therefore, in addition to its direct actions via photosynthesis and plant sensory receptors, light may affect plants indirectly via the sensory receptors of bacterial pathogens.
Collapse
Affiliation(s)
- Victoria Moriconi
- IFEVA, Facultad de Agronomía, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y Técnicas, Avenida San Martín 4453, Buenos Aires, 1417, Argentina; Fundación Instituto Leloir, Instituto de Investigaciones Bioquímicas Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, C1405BWE, Argentina
| | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Badel JL, Piquerez SJM, Greenshields D, Rallapalli G, Fabro G, Ishaque N, Jones JDG. In planta effector competition assays detect Hyaloperonospora arabidopsidis effectors that contribute to virulence and localize to different plant subcellular compartments. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:745-57. [PMID: 23734779 DOI: 10.1094/mpmi-06-12-0154-r] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The genome of the pathogenic oomycete Hyaloperonospora arabidopsidis is predicted to encode at least 134 high-confidence effectors (HaRxL) carrying the RxLR motif implicated in their translocation into plant cells. However, only four avirulence genes (ATR1, ATR13, ATR5, and ATR39) have been isolated. This indicates that identification of HaRxL effectors based on avirulence is low throughput. We aimed at rapidly identifying H. arabidopsidis effectors that contribute to virulence by developing methods to detect and quantify multiple candidates in bacterial mixed infections using either Illumina sequencing or capillary electrophoresis. In these assays, referred to here as in planta effector competition assays, we estimate the contribution to virulence of individual effectors by calculating the abundance of each HaRxL in the bacterial population recovered from leaves 3 days after inoculation relative to abundance in the initial mixed inoculum. We identified HaRxL that enhance Pseudomonas syringae pv. tomato DC3000 growth in some but not all Arabidopsis accessions. Further analysis showed that HaRxLL464, HaRxL75, HaRxL22, HaRxLL441, and HaRxL89 suppress pathogen-associated molecular pattern-triggered immunity (PTI) and localize to different subcellular compartments in Nicotiana benthamiana, providing evidence for a multilayered suppression of PTI by pathogenic oomycetes and molecular probes for the dissection of PTI.
Collapse
Affiliation(s)
- Jorge Luis Badel
- The Sainsbury Laboratory, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK
| | | | | | | | | | | | | |
Collapse
|
22
|
Worley JN, Russell AB, Wexler AG, Bronstein PA, Kvitko BH, Krasnoff SB, Munkvold KR, Swingle B, Gibson DM, Collmer A. Pseudomonas syringae pv. tomato DC3000 CmaL (PSPTO4723), a DUF1330 family member, is needed to produce L-allo-isoleucine, a precursor for the phytotoxin coronatine. J Bacteriol 2013; 195:287-96. [PMID: 23144243 PMCID: PMC3553850 DOI: 10.1128/jb.01352-12] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 10/30/2012] [Indexed: 01/12/2023] Open
Abstract
Pseudomonas syringae pv. tomato DC3000 produces the phytotoxin coronatine, a major determinant of the leaf chlorosis associated with DC3000 pathogenesis. The DC3000 PSPTO4723 (cmaL) gene is located in a genomic region encoding type III effectors; however, it promotes chlorosis in the model plant Nicotiana benthamiana in a manner independent of type III secretion. Coronatine is produced by the ligation of two moieties, coronafacic acid (CFA) and coronamic acid (CMA), which are produced by biosynthetic pathways encoded in separate operons. Cross-feeding experiments, performed in N. benthamiana with cfa, cma, and cmaL mutants, implicate CmaL in CMA production. Furthermore, analysis of bacterial supernatants under coronatine-inducing conditions revealed that mutants lacking either the cma operon or cmaL accumulate CFA rather than coronatine, supporting a role for CmaL in the regulation or biosynthesis of CMA. CmaL does not appear to regulate CMA production, since the expression of proteins with known roles in CMA production is unaltered in cmaL mutants. Rather, CmaL is needed for the first step in CMA synthesis, as evidenced by the fact that wild-type levels of coronatine production are restored to a ΔcmaL mutant when it is supplemented with 50 μg/ml l-allo-isoleucine, the starting unit for CMA production. cmaL is found in all other sequenced P. syringae strains with coronatine biosynthesis genes. This characterization of CmaL identifies a critical missing factor in coronatine production and provides a foundation for further investigation of a member of the widespread DUF1330 protein family.
Collapse
Affiliation(s)
- Jay N. Worley
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, USA
| | - Alistair B. Russell
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, USA
| | - Aaron G. Wexler
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, USA
| | - Philip A. Bronstein
- U.S. Department of Agriculture, Agricultural Research Service, Ithaca, New York, USA
| | - Brian H. Kvitko
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, USA
| | - Stuart B. Krasnoff
- U.S. Department of Agriculture, Agricultural Research Service, Ithaca, New York, USA
| | - Kathy R. Munkvold
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, USA
| | - Bryan Swingle
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, USA
- U.S. Department of Agriculture, Agricultural Research Service, Ithaca, New York, USA
| | - Donna M. Gibson
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, USA
- U.S. Department of Agriculture, Agricultural Research Service, Ithaca, New York, USA
| | - Alan Collmer
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, USA
| |
Collapse
|
23
|
Ishiga Y, Ishiga T, Wangdi T, Mysore KS, Uppalapati SR. NTRC and chloroplast-generated reactive oxygen species regulate Pseudomonas syringae pv. tomato disease development in tomato and Arabidopsis. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:294-306. [PMID: 22112219 DOI: 10.1094/mpmi-05-11-0130] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Coronatine (COR)-producing pathovars of Pseudomonas syringae, including pvs. tomato, maculicola, and glycinea, cause important diseases on tomato, crucifers, and soybean, respectively, and produce symptoms with necrotic lesions surrounded by chlorosis. The chlorosis is mainly attributed to COR. However, the significance of COR-induced chlorosis in localized lesion development and the molecular basis of disease-associated cell death is largely unknown. To identify host (chloroplast) genes that play a role in COR-mediated chlorosis, we used a forward genetics approach using Nicotiana benthamiana and virus-induced gene silencing and identified a gene which encodes 2-Cys peroxiredoxin (Prxs) that, when silenced, produced a spreading hypersensitive or necrosis-like phenotype instead of chlorosis after COR application in a COI1-dependent manner. Loss-of-function analysis of Prx and NADPH-dependent thioredoxin reductase C (NTRC), the central players of a chloroplast redox detoxification system, resulted in spreading accelerated P. syringae pv. tomato DC3000 disease-associated cell death with enhanced reactive oxygen species (ROS) accumulation in a COR-dependent manner in tomato and Arabidopsis. Consistent with these results, virulent strain DC3000 suppressed the expression of Prx and NTRC in Arabidopsis and tomato during pathogenesis. However, interestingly, authentic COR suppressed the expression of Prx and NTRC in tomato but not in Arabidopsis, suggesting that COR in conjunction with other effectors may modulate ROS and cell death in different host species. Taken together, these results indicated that NTRC or Prx function as a negative regulator of pathogen-induced cell death in the healthy tissues that surround the lesions, and COR-induced chloroplast-localized ROS play a role in enhancing the disease-associated cell death.
Collapse
Affiliation(s)
- Yasuhiro Ishiga
- Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, OK 73401, USA
| | | | | | | | | |
Collapse
|
24
|
Pseudomonas syringae pv. actinidiae draft genomes comparison reveal strain-specific features involved in adaptation and virulence to Actinidia species. PLoS One 2011; 6:e27297. [PMID: 22132095 PMCID: PMC3223175 DOI: 10.1371/journal.pone.0027297] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 10/13/2011] [Indexed: 12/22/2022] Open
Abstract
A recent re-emerging bacterial canker disease incited by Pseudomonas syringae pv. actinidiae (Psa) is causing severe economic losses to Actinidia chinensis and A. deliciosa cultivations in southern Europe, New Zealand, Chile and South Korea. Little is known about the genetic features of this pathovar. We generated genome-wide Illumina sequence data from two Psa strains causing outbreaks of bacterial canker on the A. deliciosa cv. Hayward in Japan (J-Psa, type-strain of the pathovar) and in Italy (I-Psa) in 1984 and 1992, respectively as well as from a Psa strain (I2-Psa) isolated at the beginning of the recent epidemic on A. chinensis cv. Hort16A in Italy. All strains were isolated from typical leaf spot symptoms. The phylogenetic relationships revealed that Psa is more closely related to P. s. pv. theae than to P. avellanae within genomospecies 8. Comparative genomic analyses revealed both relevant intrapathovar variations and putative pathovar-specific genomic regions in Psa. The genomic sequences of J-Psa and I-Psa were very similar. Conversely, the I2-Psa genome encodes four additional effector protein genes, lacks a 50 kb plasmid and the phaseolotoxin gene cluster, argK-tox but has acquired a 160 kb plasmid and putative prophage sequences. Several lines of evidence from the analysis of the genome sequences support the hypothesis that this strain did not evolve from the Psa population that caused the epidemics in 1984-1992 in Japan and Italy but rather is the product of a recent independent evolution of the pathovar actinidiae for infecting Actinidia spp. All Psa strains share the genetic potential for copper resistance, antibiotic detoxification, high affinity iron acquisition and detoxification of nitric oxide of plant origin. Similar to other sequenced phytopathogenic pseudomonads associated with woody plant species, the Psa strains isolated from leaves also display a set of genes involved in the catabolism of plant-derived aromatic compounds.
Collapse
|
25
|
Baltrus DA, Nishimura MT, Romanchuk A, Chang JH, Mukhtar MS, Cherkis K, Roach J, Grant SR, Jones CD, Dangl JL. Dynamic evolution of pathogenicity revealed by sequencing and comparative genomics of 19 Pseudomonas syringae isolates. PLoS Pathog 2011; 7:e1002132. [PMID: 21799664 PMCID: PMC3136466 DOI: 10.1371/journal.ppat.1002132] [Citation(s) in RCA: 300] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Accepted: 05/06/2011] [Indexed: 11/18/2022] Open
Abstract
Closely related pathogens may differ dramatically in host range, but the molecular, genetic, and evolutionary basis for these differences remains unclear. In many Gram- negative bacteria, including the phytopathogen Pseudomonas syringae, type III effectors (TTEs) are essential for pathogenicity, instrumental in structuring host range, and exhibit wide diversity between strains. To capture the dynamic nature of virulence gene repertoires across P. syringae, we screened 11 diverse strains for novel TTE families and coupled this nearly saturating screen with the sequencing and assembly of 14 phylogenetically diverse isolates from a broad collection of diseased host plants. TTE repertoires vary dramatically in size and content across all P. syringae clades; surprisingly few TTEs are conserved and present in all strains. Those that are likely provide basal requirements for pathogenicity. We demonstrate that functional divergence within one conserved locus, hopM1, leads to dramatic differences in pathogenicity, and we demonstrate that phylogenetics-informed mutagenesis can be used to identify functionally critical residues of TTEs. The dynamism of the TTE repertoire is mirrored by diversity in pathways affecting the synthesis of secreted phytotoxins, highlighting the likely role of both types of virulence factors in determination of host range. We used these 14 draft genome sequences, plus five additional genome sequences previously reported, to identify the core genome for P. syringae and we compared this core to that of two closely related non-pathogenic pseudomonad species. These data revealed the recent acquisition of a 1 Mb megaplasmid by a sub-clade of cucumber pathogens. This megaplasmid encodes a type IV secretion system and a diverse set of unknown proteins, which dramatically increases both the genomic content of these strains and the pan-genome of the species. Breakthroughs in genomics have unleashed a new suite of tools for studying the genetic bases of phenotypic differences across diverse bacterial isolates. Here, we analyze 19 genomes of P. syringae, a pathogen of many crop species, to reveal the genetic changes underlying differences in virulence across host plants ranging from rice to maple trees. Surprisingly, a pair of strains diverged dramatically via the acquisition of a 1 Mb megaplasmid, which constitutes roughly 14% of the genome. Novel plasmids and horizontal genetic exchange have contributed extensively to species-wide diversification. Type III effector proteins are essential for pathogenicity, exhibit wide diversity between strains and are present in distinct higher-level patterns across the species. Furthermore, we use sequence comparisons within an evolutionary context to identify functional changes in multiple virulence genes. Overall, our data provide a unique overview of evolutionary pressures within P. syringae and an important resource for the phytopathogen research community.
Collapse
Affiliation(s)
- David A. Baltrus
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Marc T. Nishimura
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Artur Romanchuk
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Jeff H. Chang
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - M. Shahid Mukhtar
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Karen Cherkis
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Jeff Roach
- Research Computing Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Sarah R. Grant
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Corbin D. Jones
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Carolina Center for Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail: (CDJ, computational queries); (JLD, biological queries)
| | - Jeffery L. Dangl
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Carolina Center for Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail: (CDJ, computational queries); (JLD, biological queries)
| |
Collapse
|
26
|
Salomon D, Dar D, Sreeramulu S, Sessa G. Expression of Xanthomonas campestris pv. vesicatoria type III effectors in yeast affects cell growth and viability. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2011; 24:305-14. [PMID: 21062109 DOI: 10.1094/mpmi-09-10-0196] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The gram-negative bacterium Xanthomonas campestris pv. vesicatoria is the causal agent of spot disease in tomato and pepper. X. campestris pv. vesicatoria pathogenicity depends on a type III secretion system delivering effector proteins into the host cells. We hypothesized that some X. campestris pv. vesicatoria effectors target conserved eukaryotic cellular processes and examined phenotypes induced by their expression in yeast. Out of 21 effectors tested, 14 inhibited yeast growth in normal or stress conditions. Viability assay revealed that XopB and XopF2 attenuated cell proliferation, while AvrRxo1, XopX, and XopE1 were cytotoxic. Inspection of morphological features and DNA content of yeast cells indicated that cytotoxicity caused by XopX and AvrRxo1 was associated with cell-cycle arrest at G0/1. Interestingly, XopB, XopE1, XopF2, XopX, and AvrRxo1 that inhibited growth in yeast also caused phenotypes, such as chlorosis and cell death, when expressed in either host or nonhost plants. Finally, the ability of several effectors to cause phenotypes in yeast and plants was dependent on their putative catalytic residues or localization motifs. This study supports the use of yeast as a heterologous system for functional analysis of X. campestris pv. vesicatoria type III effectors, and sets the stage for identification of their eukaryotic molecular targets and modes of action.
Collapse
Affiliation(s)
- Dor Salomon
- Department of Molecular Biology, Tel-Aviv University, Tel-Aviv, Israel
| | | | | | | |
Collapse
|
27
|
Uppalapati SR, Ishiga Y, Ryu CM, Ishiga T, Wang K, Noël LD, Parker JE, Mysore KS. SGT1 contributes to coronatine signaling and Pseudomonas syringae pv. tomato disease symptom development in tomato and Arabidopsis. THE NEW PHYTOLOGIST 2011; 189:83-93. [PMID: 20854394 DOI: 10.1111/j.1469-8137.2010.03470.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
• Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) causes an economically important bacterial speck disease on tomato and produces symptoms with necrotic lesions surrounded by chlorosis. The chlorosis is mainly attributed to a jasmonic acid (JA)-isoleucine analogue, coronatine (COR), produced by Pst DC3000. However, the molecular processes underlying lesion development and COR-induced chlorosis are poorly understood. • In this study, we took advantage of a chlorotic phenotype elicited by COR on Nicotiana benthamiana leaves and virus-induced gene silencing (VIGS) as a rapid reverse genetic screening tool and identified a role for SGT1 (suppressor of G2 allele of skp1) in COR-induced chlorosis. • Silencing of SGT1 in tomato resulted in reduction of disease-associated symptoms (cell death and chlorosis), suggesting a molecular connection between COR-induced chlorosis and cell death. In Arabidopsis, AtSGT1b but not AtSGT1a was required for COR responses, including root growth inhibition and Pst DC3000 symptom (water soaked lesion) development. Notably, overexpression of AtSGT1b did not alter Pst DC3000 symptoms or sensitivity to COR. • Taken together, our results demonstrate that SGT1/SGT1b is required for COR-induced chlorosis and subsequent necrotic disease development in tomato and Arabidopsis. SGT1 is therefore a component of the COR/JA-mediated signal transduction pathway.
Collapse
|
28
|
Macho AP, Beuzón CR. Insights into plant immunity signalling: the bacterial competitive index angle. PLANT SIGNALING & BEHAVIOR 2010; 5:1590-1593. [PMID: 21150288 PMCID: PMC3115109 DOI: 10.4161/psb.5.12.13843] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2010] [Accepted: 10/03/2010] [Indexed: 05/30/2023]
Abstract
The interaction between a bacterial pathogen and its potential plant host develops from a complex combination of bacterial and plant elements, which determines either the establishment of resistance or the development of disease. The use of virulence assays based on competitive index in mixed infections constitutes a powerful tool for the analysis of bacterial virulence factors. In this work, we describe how the use of competitive index assays also constitutes an alternative approach for the analysis of plant immunity, to determine the contribution of different elements to bacterial recognition or immunity signaling.
Collapse
Affiliation(s)
- Alberto P Macho
- Instituto de Hortofruticultura Subtropical y Mediterránea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Depto. Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga, Spain
| | | |
Collapse
|
29
|
Hann DR, Rathjen JP. The long and winding road: virulence effector proteins of plant pathogenic bacteria. Cell Mol Life Sci 2010; 67:3425-34. [PMID: 20549537 PMCID: PMC11115680 DOI: 10.1007/s00018-010-0428-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Revised: 05/31/2010] [Accepted: 06/01/2010] [Indexed: 12/11/2022]
Abstract
Plant pathogenic bacteria inject about 30 virulence effector proteins into the host cell using a specialized secretion apparatus. Bacteria which are unable to do this elicit host immunity and cannot grow inside living plant tissue. Thus, the primary function of the effectors is to suppress host immunity. The identity of individual effectors within each complement varies even between closely related bacterial strains, and effectors themselves act redundantly and are apparently interchangeable. Many effectors are known to target components of plant defense pathways, but it is difficult to study their role in molecular terms. For some of them, there is controversy about their mode of action. We propose that effectors act promiscuously by targeting host molecules with low specificity and affinity.
Collapse
Affiliation(s)
- Dagmar R. Hann
- Section of Plant Physiology, Botanical Institute, University of Basel, Hebelstrasse 1, 4056 Basel, Switzerland
| | - John P. Rathjen
- Research School of Biology, The Australian National University, RN Robertson Building, Biology Place, Acton, ACT 0200 Australia
| |
Collapse
|