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Child HT, Deeks MJ, Rudd JJ, Bates S. Comparison of the impact of two key fungal signalling pathways on Zymoseptoria tritici infection reveals divergent contribution to invasive growth through distinct regulation of infection-associated genes. Mol Plant Pathol 2023; 24:1220-1237. [PMID: 37306534 PMCID: PMC10502814 DOI: 10.1111/mpp.13365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 05/12/2023] [Accepted: 05/23/2023] [Indexed: 06/13/2023]
Abstract
The lifecycle of Zymoseptoria tritici requires a carefully regulated asymptomatic phase within the wheat leaf following penetration of the mesophyll via stomata. Here we compare the roles in this process of two key fungal signalling pathways, mutants of which were identified through forward genetics due to their avirulence on wheat. Whole-genome resequencing of avirulent Z. tritici T-DNA transformants identified disruptive mutations in ZtBCK1 from the kinase cascade of the cell wall integrity (CWI) pathway, and the adenylate cyclase gene ZtCYR1. Targeted deletion of these genes abolished the pathogenicity of the fungus and led to similar in vitro phenotypes to those associated with disruption of putative downstream kinases, both supporting previous studies and confirming the importance of these pathways in virulence. RNA sequencing was used to investigate the effect of ZtBCK1 and ZtCYR1 deletion on gene expression in both the pathogen and host during infection. ZtBCK1 was found to be required for the adaptation to the host environment, controlling expression of infection-associated secreted proteins, including known virulence factors. Meanwhile, ZtCYR1 is implicated in controlling the switch to necrotrophy, regulating expression of effectors associated with this transition. This represents the first study to compare the influence of CWI and cAMP signalling on in planta transcription of a fungal plant pathogen, providing insights into their differential regulation of candidate effectors during invasive growth.
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Affiliation(s)
| | | | - Jason J. Rudd
- Department of Protecting Crops and the EnvironmentRothamsted ResearchHarpendenUK
| | - Steven Bates
- Department of BiosciencesUniversity of ExeterExeterUK
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2
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Wang C, Milgate AW, Solomon PS, McDonald MC. The identification of a transposon affecting the asexual reproduction of the wheat pathogen Zymoseptoria tritici. Mol Plant Pathol 2021; 22:800-816. [PMID: 33949756 PMCID: PMC8232023 DOI: 10.1111/mpp.13064] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 03/15/2021] [Accepted: 03/16/2021] [Indexed: 05/13/2023]
Abstract
Zymoseptoria tritici, the causal agent of Septoria tritici blotch, is a fungal wheat pathogen that causes significant global yield losses. Within Z. tritici populations, quantitative differences in virulence among different isolates are commonly observed; however, the genetic components that underpin these differences remain elusive. In this study, intraspecific comparative transcriptomic analysis was used to identify candidate genes that contribute to differences in virulence on the wheat cultivar WW2449. This led to the identification of a multicopy gene that was not expressed in the high-virulence isolate when compared to the medium- and low-virulence isolates. Further investigation suggested this gene resides in a 7.9-kb transposon. Subsequent long-read sequencing of the isolates used in the transcriptomic analysis confirmed that this gene did reside in an active Class II transposon, which is composed of four genes named REP9-1 to -4. Silencing and overexpression of REP9-1 in two distinct genetic backgrounds demonstrated that its expression alone reduces the number of pycnidia produced by Z. tritici during infection. The REP9-1 gene identified within a Class II transposon is the first discovery of a gene in a transposable element that influences the virulence of Z. tritici. This discovery adds further complexity to genetic loci that contribute to quantitative virulence in this important pathogen.
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Affiliation(s)
- Chen Wang
- Division of Plant SciencesResearch School of BiologyThe Australian National UniversityCanberraACTAustralia
| | - Andrew W. Milgate
- NSW Department of Primary IndustriesWagga Wagga Agricultural InstituteWagga WaggaNSWAustralia
| | - Peter S. Solomon
- Division of Plant SciencesResearch School of BiologyThe Australian National UniversityCanberraACTAustralia
| | - Megan C. McDonald
- Division of Plant SciencesResearch School of BiologyThe Australian National UniversityCanberraACTAustralia
- School of BiosciencesUniversity of BirminghamEdgbastonBirminghamUK
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3
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Garnault M, Duplaix C, Leroux P, Couleaud G, David O, Walker AS, Carpentier F. Large-scale study validates that regional fungicide applications are major determinants of resistance evolution in the wheat pathogen Zymoseptoria tritici in France. New Phytol 2021; 229:3508-3521. [PMID: 33226662 DOI: 10.1111/nph.17107] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 11/16/2020] [Indexed: 06/11/2023]
Abstract
In modern cropping systems, the near-universal use of plant protection products selects for resistance in pest populations. The emergence and evolution of this adaptive trait threaten treatment efficacy. We identified determinants of fungicide resistance evolution and quantified their effects at a large spatiotemporal scale. We focused on Zymoseptoria tritici, which causes leaf blotch in wheat. Phenotypes of qualitative or quantitative resistance to various fungicides were monitored annually, from 2004 to 2017, at about 70 sites throughout 22 regions of France (territorial units of 25 000 km2 on average). We modelled changes in resistance frequency with regional anti-Septoria fungicide use, yield losses due to the disease and the regional area under organic wheat. The major driver of resistance dynamics was fungicide use at the regional scale. We estimated its effect on the increase in resistance and relative apparent fitness of each resistance phenotype. The predictions of the model replicated the spatiotemporal patterns of resistance observed in field populations (R2 from 0.56 to 0.82). The evolution of fungicide resistance is mainly determined at the regional scale. This study therefore showed that collective management at the regional scale could effectively complete local actions.
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Affiliation(s)
- Maxime Garnault
- AgroParisTech, UMR BIOGER, INRAE, Université Paris-Saclay, Thiverval-Grignon, 78850, France
- MaIAGE, INRAE, Université Paris-Saclay, Jouy-en-Josas, 78350, France
| | - Clémentine Duplaix
- AgroParisTech, UMR BIOGER, INRAE, Université Paris-Saclay, Thiverval-Grignon, 78850, France
| | - Pierre Leroux
- AgroParisTech, UMR BIOGER, INRAE, Université Paris-Saclay, Thiverval-Grignon, 78850, France
| | | | - Olivier David
- MaIAGE, INRAE, Université Paris-Saclay, Jouy-en-Josas, 78350, France
| | - Anne-Sophie Walker
- AgroParisTech, UMR BIOGER, INRAE, Université Paris-Saclay, Thiverval-Grignon, 78850, France
| | - Florence Carpentier
- AgroParisTech, UMR BIOGER, INRAE, Université Paris-Saclay, Thiverval-Grignon, 78850, France
- MaIAGE, INRAE, Université Paris-Saclay, Jouy-en-Josas, 78350, France
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4
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Mikaberidze A, McDonald BA. A tradeoff between tolerance and resistance to a major fungal pathogen in elite wheat cultivars. New Phytol 2020; 226:879-890. [PMID: 31917858 DOI: 10.1111/nph.16418] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 12/12/2019] [Indexed: 06/10/2023]
Abstract
Tolerance and resistance represent two strategies that hosts evolved to protect themselves from pathogens. Tolerance alleviates the reduction in host fitness due to infection without reducing a pathogen's growth, whereas resistance reduces pathogen growth. We investigated the tolerance of wheat to the major fungal pathogen Zymoseptoria tritici in 335 elite wheat cultivars. We used a novel digital phenotyping approach that included 11 152 infected leaves and counted 2069 048 pathogen fruiting bodies. We discovered a new component of tolerance that is based on the relationship between the green area remaining on a leaf and the number of pathogen fruiting bodies. We found a negative correlation between tolerance and resistance among intolerant cultivars, presenting the first compelling evidence for a tradeoff between tolerance and resistance to plant pathogens. Surprisingly, the tradeoff arises due to limits in the host resources available to the pathogen and not due to metabolic constraints, contrary to what ecological theory suggests. The mechanism underlying this tradeoff may be relevant for many plant diseases in which the amount of host resources available to the pathogen can limit the pathogen population. Our analysis indicates that European wheat breeders may have selected for tolerance instead of resistance to an important pathogen.
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Affiliation(s)
- Alexey Mikaberidze
- School of Agriculture, Policy and Development, University of Reading, Whiteknights, Reading, RG6 6AR, UK
| | - Bruce A McDonald
- Plant Pathology, Institute of Integrative Biology, LFW, ETH Zurich, 8092, Zurich, Switzerland
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Hagerty CH, Graebner RC, Sackett KE, Mundt CC. Variable competitive effects of fungicide resistance in field experiments with a plant pathogenic fungus. Ecol Appl 2017; 27:1305-1316. [PMID: 28266146 DOI: 10.1002/eap.1524] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Revised: 01/26/2017] [Accepted: 02/06/2017] [Indexed: 06/06/2023]
Abstract
Classic evolutionary theory suggests that mutations associated with antimicrobial and pesticide resistance result in a fitness cost in the absence of the selective antimicrobial agent or pesticide. There is experimental evidence to support fitness costs associated with resistance to anti-microbial compounds and pesticides across many biological disciplines, including human pathology, entomology, plant sciences, and plant pathology. However, researchers have also found examples of neutral and increased fitness associated with resistance, where the effect of a given resistance mutation depends on environmental and biological factors. We used Zymoseptoria tritici, a model evolutionary plant pathogenic fungus, to compare the competitive ability of fungicide-resistant isolates to fungicide-sensitive isolates. We conducted four large-scale inoculated winter wheat experiments at Oregon State University agriculture experiment stations. We found a significant change in the frequency of fungicide resistance over time in all four experiments. The direction and magnitude of these changes, however, differed by experimental location, year of experiment, and inoculum resistance treatment (fungicide-resistant, resistant/sensitive mixture, and fungicide-sensitive). These results suggest that the competitive ability of resistant isolates relative to sensitive isolates varied depending upon environmental conditions, including the initial frequency of resistant individuals in the population.
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Affiliation(s)
- Christina H Hagerty
- Columbia Basin Agricultural Research Center, Oregon State University, 48037 Tubbs Ranch Road, Adams, OR, 97801, USA
| | - Ryan C Graebner
- Hermiston Agricultural Research and Extension Center, Oregon State University, 2121 S 1st St, Hermiston, OR, 97838, USA
| | - Kathryn E Sackett
- Department of Botany and Plant Pathology, Oregon State University, Cordley Hall, 2701 SW Campus Way, Corvallis, OR, 97331, USA
| | - Christopher C Mundt
- Department of Botany and Plant Pathology, Oregon State University, Cordley Hall, 2701 SW Campus Way, Corvallis, OR, 97331, USA
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Zhong Z, Marcel TC, Hartmann FE, Ma X, Plissonneau C, Zala M, Ducasse A, Confais J, Compain J, Lapalu N, Amselem J, McDonald BA, Croll D, Palma-Guerrero J. A small secreted protein in Zymoseptoria tritici is responsible for avirulence on wheat cultivars carrying the Stb6 resistance gene. New Phytol 2017; 214:619-631. [PMID: 28164301 DOI: 10.1111/nph.14434] [Citation(s) in RCA: 121] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 12/09/2016] [Indexed: 05/06/2023]
Abstract
Zymoseptoria tritici is the causal agent of Septoria tritici blotch, a major pathogen of wheat globally and the most damaging pathogen of wheat in Europe. A gene-for-gene (GFG) interaction between Z. tritici and wheat cultivars carrying the Stb6 resistance gene has been postulated for many years, but the genes have not been identified. We identified AvrStb6 by combining quantitative trait locus mapping in a cross between two Swiss strains with a genome-wide association study using a natural population of c. 100 strains from France. We functionally validated AvrStb6 using ectopic transformations. AvrStb6 encodes a small, cysteine-rich, secreted protein that produces an avirulence phenotype on wheat cultivars carrying the Stb6 resistance gene. We found 16 nonsynonymous single nucleotide polymorphisms among the tested strains, indicating that AvrStb6 is evolving very rapidly. AvrStb6 is located in a highly polymorphic subtelomeric region and is surrounded by transposable elements, which may facilitate its rapid evolution to overcome Stb6 resistance. AvrStb6 is the first avirulence gene to be functionally validated in Z. tritici, contributing to our understanding of avirulence in apoplastic pathogens and the mechanisms underlying GFG interactions between Z. tritici and wheat.
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Affiliation(s)
- Ziming Zhong
- Plant Pathology Group, ETH Zürich, Universitätstrasse 2, 8092, Zürich, Switzerland
| | - Thierry C Marcel
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France
| | - Fanny E Hartmann
- Plant Pathology Group, ETH Zürich, Universitätstrasse 2, 8092, Zürich, Switzerland
| | - Xin Ma
- Plant Pathology Group, ETH Zürich, Universitätstrasse 2, 8092, Zürich, Switzerland
| | - Clémence Plissonneau
- Plant Pathology Group, ETH Zürich, Universitätstrasse 2, 8092, Zürich, Switzerland
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France
| | - Marcello Zala
- Plant Pathology Group, ETH Zürich, Universitätstrasse 2, 8092, Zürich, Switzerland
| | - Aurélie Ducasse
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France
| | - Johann Confais
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France
| | - Jérôme Compain
- UR URGI, INRA, Université Paris-Saclay, 78026, Versailles, France
| | - Nicolas Lapalu
- UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France
- UR URGI, INRA, Université Paris-Saclay, 78026, Versailles, France
| | - Joëlle Amselem
- UR URGI, INRA, Université Paris-Saclay, 78026, Versailles, France
| | - Bruce A McDonald
- Plant Pathology Group, ETH Zürich, Universitätstrasse 2, 8092, Zürich, Switzerland
| | - Daniel Croll
- Plant Pathology Group, ETH Zürich, Universitätstrasse 2, 8092, Zürich, Switzerland
- Laboratory of Evolutionary Genetics, University of Neuchâtel Institute of Biology Rue Emile-Argand 11, CH-2000, Neuchâtel, Switzerland
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7
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Affiliation(s)
- Peter S Solomon
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra, 2601, ACT, Australia
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Kettles GJ, Bayon C, Canning G, Rudd JJ, Kanyuka K. Apoplastic recognition of multiple candidate effectors from the wheat pathogen Zymoseptoria tritici in the nonhost plant Nicotiana benthamiana. New Phytol 2017; 213:338-350. [PMID: 27696417 PMCID: PMC5132004 DOI: 10.1111/nph.14215] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 08/19/2016] [Indexed: 05/18/2023]
Abstract
The fungus Zymoseptoria tritici is a strictly apoplastic, host-specific pathogen of wheat leaves and causal agent of septoria tritici blotch (STB) disease. All other plants are considered nonhosts, but the mechanism of nonhost resistance (NHR) to Z. tritici has not been addressed previously. We sought to develop Nicotiana benthamiana as a system to study NHR against Z. tritici. Fluorescence microscopy and quantitative reverse transcription polymerase chain reactions were used to establish the interaction between Z. tritici and N. benthamiana. Agrobacterium-mediated transient expression was used to screen putative Z. tritici effector genes for recognition in N. benthamiana, and virus-induced gene silencing (VIGS) was employed to determine the role of two receptor-like kinases (RLKs), NbBAK1 and NbSOBIR1, in Z. tritici effector recognition. Numerous Z. tritici putative effectors (14 of 63 tested) induced cell death or chlorosis in N. benthamiana. For most, phenotypes were light-dependent and required effector secretion to the leaf apoplastic space. Moreover, effector-induced host cell death was dependent on NbBAK1 and NbSOBIR1. Our results indicate widespread recognition of apoplastic effectors from a wheat-infecting fungal pathogen in a taxonomically distant nonhost plant species presumably by cell surface immune receptors. This suggests that apoplastic recognition of multiple nonadapted pathogen effectors may contribute to NHR.
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Affiliation(s)
- Graeme J. Kettles
- Department of Plant Biology & Crop ScienceRothamsted ResearchHarpendenHertfordshireAL5 2JQUK
| | - Carlos Bayon
- Department of Plant Biology & Crop ScienceRothamsted ResearchHarpendenHertfordshireAL5 2JQUK
| | - Gail Canning
- Department of Plant Biology & Crop ScienceRothamsted ResearchHarpendenHertfordshireAL5 2JQUK
| | - Jason J. Rudd
- Department of Plant Biology & Crop ScienceRothamsted ResearchHarpendenHertfordshireAL5 2JQUK
| | - Kostya Kanyuka
- Department of Plant Biology & Crop ScienceRothamsted ResearchHarpendenHertfordshireAL5 2JQUK
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9
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Abstract
This article is a Commentary on Kettles et al., 213: 338–350.
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Affiliation(s)
- Timothy L Friesen
- Cereal Crop Research Unit, United States Department of Agriculture - Agricultural Research Service, Fargo, ND, 58102-2765, USA
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