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Molecular analysis of three different types of fungal disease resistance mechanisms in cereals

English title Molecular analysis of three different types of fungal disease resistance mechanisms in cereals
Applicant Keller Beat
Number 163260
Funding scheme Project funding
Research institution Institut für Pflanzen- und Mikrobiologie Universität Zürich
Institution of higher education University of Zurich - ZH
Main discipline Botany
Start/End 01.01.2016 - 31.12.2018
Approved amount 924'003.00
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Keywords (10)

wheat; avirulence; fungal pathogens ; receptor-like kinase; durable resistance; maize; rice; disease resistance; effectors; host specificity

Lay Summary (German)

Lead
Pflanzen werden von einer Vielzahl von Krankheitserregern befallen. Die Züchtung von Nutzpflanzen hat im Verlauf der letzten 100 Jahre zur Entdeckung von natürlicherweise vorkommender Resistenz gegen Pathogene geführt. Die Funktionsweisen dieser Resistenzen sind auf molekularer Ebene noch wenig verstanden. Das Projekt soll dazu wichtige Erkenntnisse liefern.
Lay summary

Wir haben in den letzten Jahren in Weizen und Mais drei molekular sehr unterschiedliche Resistenzmechanismen gegen pilzliche Krankheitserreger entdeckt. Dabei handelt es sich um Abwehrstrategien, die entweder spezifische Moleküle der mikrobiellen Invasoren entdecken können, oder aber den Stoffwechsel der Pflanze so verändern, dass die Pathogene nicht mehr wachsen können.

Im vorliegenden Projekt sollen die Erkennungsmechanismen in Mais durch das Htn1 Gen gegen die Helminthosporium-Blattfleckenkrankheit sowie in Weizen durch das Pm3 Gen gegen Mehltau analysiert werden. Für das Pm3 Gen kennen wir inzwischen ein Protein aus dem Pathogen, das spezifisch erkannt wird. Dies erlaubt es, eine genaue molekulare Beschreibung der Interaktion der beiden Moleküle und damit des Erkennungsmechanismus zwischen Pflanze und Krankheitserreger anzustreben. Schliesslich sollen die physiologischen Veränderungen in Weizensorten erforscht werden, die das Lr34 Gen enthalten. Lr34 vermittelt eine Resistenz gegenüber verschiedenen Pilzarten und stellt damit eines der interessantesten und bedeutendsten Resistenzgene dar.

Das Projekt beschäftigt sich mit der biologischen Funktionsweise von Krankheitsresistenz bei Getreide und leistet einen wichtigen Beitrag zu einer sehr dynamischen, global relevanten Forschungsrichtung. Da Pflanzenkrankheiten und ihre Bekämpfung ökonomisch wie ökologisch von grosser Bedeutung sind, steht diese Forschungsrichtung auch im Brennpunkt gesellschaftlicher Aufmerksamkeit.

 

Direct link to Lay Summary Last update: 30.10.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Single residues in the LRR domain of the wheat PM3A immune receptor can control the strength and the spectrum of the immune response
Lindner Stefan, Keller Bettina, Singh Simrat P., Hasenkamp Zsuzsanna, Jung Esther, Müller Marion C., Bourras Salim, Keller Beat (2020), Single residues in the LRR domain of the wheat PM3A immune receptor can control the strength and the spectrum of the immune response, in The Plant Journal, 104(1), 200-214.
The AvrPm3-Pm3 effector-NLR interactions control both race-specific resistance and host-specificity of cereal mildews on wheat
Bourras Salim, Kunz Lukas, Xue Minfeng, Praz Coraline Rosalie, Müller Marion Claudia, Kälin Carol, Schläfli Michael, Ackermann Patrick, Flückiger Simon, Parlange Francis, Menardo Fabrizio, Schaefer Luisa Katharina, Ben-David Roi, Roffler Stefan, Oberhaensli Simone, Widrig Victoria, Lindner Stefan, Isaksson Jonatan, Wicker Thomas, Yu Dazhao, Keller Beat (2019), The AvrPm3-Pm3 effector-NLR interactions control both race-specific resistance and host-specificity of cereal mildews on wheat, in Nature Communications, 10(1), 2292-2292.
Abscisic acid is a substrate of the ABC transporter encoded by the durable wheat disease resistance gene Lr34
Krattinger Simon G., Kang Joohyun, Bräunlich Stephanie, Boni Rainer, Chauhan Harsh, Selter Liselotte L., Robinson Mark D., Schmid Marc W., Wiederhold Elena, Hensel Goetz, Kumlehn Jochen, Sucher Justine, Martinoia Enrico, Keller Beat (2019), Abscisic acid is a substrate of the ABC transporter encoded by the durable wheat disease resistance gene Lr34, in New Phytologist, 223(2), 853-866.
Field grown transgenic Pm3e wheat lines show powdery mildew resistance and no fitness costs associated with high transgene expression
Koller Teresa, Brunner Susanne, Herren Gerhard, Sanchez-Martin Javier, Hurni Severine, Keller Beat (2019), Field grown transgenic Pm3e wheat lines show powdery mildew resistance and no fitness costs associated with high transgene expression, in Transgenic Research, 28(1), 9-20.
Fungal resistance mediated by maize wall-associated kinase ZmWAK-RLK1 correlates with reduced benzoxazinoid content
Yang Ping, Praz Coraline, Li Beibei, Singla Jyoti, Robert Christelle A. M., Kessel Bettina, Scheuermann Daniela, Lüthi Linda, Ouzunova Milena, Erb Matthias, Krattinger Simon G., Keller Beat (2019), Fungal resistance mediated by maize wall-associated kinase ZmWAK-RLK1 correlates with reduced benzoxazinoid content, in New Phytologist, 221(2), 976-987.
A chromosome-scale genome assembly reveals a highly dynamic effector repertoire of wheat powdery mildew
Müller Marion C., Praz Coraline R., Sotiropoulos Alexandros G., Menardo Fabrizio, Kunz Lukas, Schudel Seraina, Oberhänsli Simone, Poretti Manuel, Wehrli Andreas, Bourras Salim, Keller Beat, Wicker Thomas (2018), A chromosome-scale genome assembly reveals a highly dynamic effector repertoire of wheat powdery mildew, in New Phytologist, -.
Evolutionary divergence of the rye Pm17 and Pm8 resistance genes reveals ancient diversity
Singh Simrat Pal, Hurni Severine, Ruinelli Michela, Brunner Susanne, Sanchez-Martin Javier, Krukowski Patricia, Peditto David, Buchmann Gabriele, Zbinden Helen, Keller Beat (2018), Evolutionary divergence of the rye Pm17 and Pm8 resistance genes reveals ancient diversity, in Plant Molecular Biology, 98(3), 249-260.
Advances in Wheat and Pathogen Genomics: Implications for Disease Control
Keller Beat, Wicker Thomas, Krattinger Simon G. (2018), Advances in Wheat and Pathogen Genomics: Implications for Disease Control, in Annual Review of Phytopathology, 56(1), 67-87.
Transcriptional profiling reveals no response of fungal pathogens to the durable, quantitative Lr34 disease resistance gene of wheat
Sucher J., Menardo F., Praz C. R., Boni R., Krattinger S. G., Keller B. (2018), Transcriptional profiling reveals no response of fungal pathogens to the durable, quantitative Lr34 disease resistance gene of wheat, in Plant Pathology, 67(4), 792-798.
Distinct domains of the AVRPM3 A2/F2 avirulence protein from wheat powdery mildew are involved in immune receptor recognition and putative effector function
McNally Kaitlin Elyse, Menardo Fabrizio, Lüthi Linda, Praz Coraline Rosalie, Müller Marion Claudia, Kunz Lukas, Ben-David Roi, Chandrasekhar Kottakota, Dinoor Amos, Cowger Christina, Meyers Emily, Xue Mingfeng, Zeng Fangsong, Gong Shuangjun, Yu Dazhao, Bourras Salim, Keller Beat (2018), Distinct domains of the AVRPM3 A2/F2 avirulence protein from wheat powdery mildew are involved in immune receptor recognition and putative effector function, in New Phytologist, 218(2), 681-695.
Pyramiding of transgenic Pm3 alleles in wheat results in improved powdery mildew resistance in the field
Koller Teresa, Brunner Susanne, Herren Gerhard, Hurni Severine, Keller Beat (2018), Pyramiding of transgenic Pm3 alleles in wheat results in improved powdery mildew resistance in the field, in Theoretical and Applied Genetics, 131(4), 861-871.
Non-parent of Origin Expression of Numerous Effector Genes Indicates a Role of Gene Regulation in Host Adaption of the Hybrid Triticale Powdery Mildew Pathogen
Praz Coraline R., Menardo Fabrizio, Robinson Mark D., Müller Marion C., Wicker Thomas, Bourras Salim, Keller Beat (2018), Non-parent of Origin Expression of Numerous Effector Genes Indicates a Role of Gene Regulation in Host Adaption of the Hybrid Triticale Powdery Mildew Pathogen, in Frontiers in Plant Science, 9, -.
Pathogen-inducible Ta - Lr34res expression in heterologous barley confers disease resistance without negative pleiotropic effects
Boni Rainer, Chauhan Harsh, Hensel Goetz, Roulin Anne, Sucher Justine, Kumlehn Jochen, Brunner Susanne, Krattinger Simon G., Keller Beat (2018), Pathogen-inducible Ta - Lr34res expression in heterologous barley confers disease resistance without negative pleiotropic effects, in Plant Biotechnology Journal, 16(1), 245-253.
Rapid turnover of effectors in grass powdery mildew (Blumeria graminis)
Menardo Fabrizio, Praz Coraline R., Wicker Thomas, Keller Beat (2017), Rapid turnover of effectors in grass powdery mildew (Blumeria graminis), in BMC Evolutionary Biology, 17(1), 223-223.
Rapid turnover of effectors in grass powdery mildew (Blumeria graminis)
Menardo Fabrizio, Praz Coraline R., Wicker Thomas, Keller Beat (2017), Rapid turnover of effectors in grass powdery mildew (Blumeria graminis), in BMC Evolutionary Biology, 17(1), 223-223.
AvrPm2 encodes an RNase-like avirulence effector which is conserved in the two different specialized forms of wheat and rye powdery mildew fungus
Praz Coraline R., Bourras Salim, Zeng Fansong, Sánchez-Martín Javier, Menardo Fabrizio, Xue Minfeng, Yang Lijun, Roffler Stefan, Böni Rainer, Herren Gerard, McNally Kaitlin E., Ben-David Roi, Parlange Francis, Oberhaensli Simone, Flückiger Simon, Schäfer Luisa K., Wicker Thomas, Yu Dazhao, Keller Beat (2017), AvrPm2 encodes an RNase-like avirulence effector which is conserved in the two different specialized forms of wheat and rye powdery mildew fungus, in New Phytologist, 213(3), 1301-1314.
Reconstructing the Evolutionary History of Powdery Mildew Lineages (Blumeria graminis) at Different Evolutionary Time Scales with NGS Data
Menardo Fabrizio, Wicker Thomas, Keller Beat (2017), Reconstructing the Evolutionary History of Powdery Mildew Lineages (Blumeria graminis) at Different Evolutionary Time Scales with NGS Data, in Genome Biology and Evolution, 9(2), 446-456.
Rapid gene isolation in barley and wheat by mutant chromosome sequencing
Sánchez-Martín Javier, Steuernagel Burkhard, Ghosh Sreya, Herren Gerhard, Hurni Severine, Adamski Nikolai, Vrána Jan, Kubaláková Marie, Krattinger Simon G., Wicker Thomas, Doležel Jaroslav, Keller Beat, Wulff Brande B. H. (2016), Rapid gene isolation in barley and wheat by mutant chromosome sequencing, in Genome Biology, 17(1), 221-221.
Avirulence Genes in Cereal Powdery Mildews: The Gene-for-Gene Hypothesis 2.0
Bourras Salim, McNally Kaitlin E., Müller Marion C., Wicker Thomas, Keller Beat (2016), Avirulence Genes in Cereal Powdery Mildews: The Gene-for-Gene Hypothesis 2.0, in Frontiers in Plant Science, 7, 241.

Collaboration

Group / person Country
Types of collaboration
Dr. Hana Simkova, Institute of Experimental Botany, Olomouc Czech Republic (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Dr. Mark Banfield, John Innes Centre, Norwich Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Enrico Martinoia, Institute of Plant Biology, University of Zürich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
Prof. Dr. Bruce McDonald, ETH Zürich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Dr. Cristina Cowger, United States Department of Agriculture United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Dr. Markus Aebi, ETH Zürich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Breakthroughs in Plant Sciences - Symposium of the Zurich-Basel Plant Science Center, Zürich, Switzerland Talk given at a conference Highlighting the achievements of the PSC in the past 20 years 05.12.2018 Zurich, Switzerland Keller Beat;
Schweiz. Botanische Gesellschaft, Symposium "Les Plantes et l'Alimentation", Lausanne, Switzerland Talk given at a conference Pflanzenzüchtung: klassische und molekulare Ansätze zur Verbesserung von Kulturpflanzen 10.11.2018 Lausanne, Switzerland Keller Beat;
Plant Receptor Kinases and Related Pathways, Zürich, Switzerland Talk given at a conference WAK receptor kinases encoded by disease resistance genes 30.10.2018 Zurich, Switzerland Keller Beat;
WHEALBI Consortium Meeting, Edinburgh, Scotland Talk given at a conference Genome-wide association analysis uncovers new sources of resistance to wheat powdery mildew 24.10.2018 Edinburgh, Great Britain and Northern Ireland Sanchez Martin Javier;
15th International Cereal Rusts and Powdery Mildews Conference, Skukuza, South Africa Talk given at a conference Molecular components of the wheat-powdery mildew interaction are efficiently identified by novel genomic tools 23.09.2018 Skukuza, South Africa Keller Beat;
Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) - Guest speaker, Gaterleben, Germany Individual talk Shifting paradigm in disease resistance: from Flor's gene-for-gene model to disease interaction networks 21.06.2018 Gatersleben, Germany Bourras Salim;
6th Plant Genomics and Gene Editing Congress, Rotterdam, Netherlands Talk given at a conference Genomics-based improvement of fungal pathogen resistance in wheat and other cereal crops 14.05.2018 Rotterdam, Netherlands Keller Beat;
EUCARPIA cereal section / IWIW2 Meeting, Polydome-Clermont-Ferrand, France Talk given at a conference GWAS reveals new race-specific resistance genes to powdery mildew in wheat 19.03.2018 Polydome-Clermont-Ferrand, France Sanchez Martin Javier;
Swiss Plant Science Web (SPSW), SwissPlant Symposium, Meiringen, Switzerland Talk given at a conference From Flor's gene-for-gene model to effector-NLR interactomes 31.01.2018 Meiringen, Switzerland Bourras Salim;
Agricultural Genomics - Functional Genomics Towards Green Crops for Sustainable Agriculture, Nature Conferences, Wuhan, China Talk given at a conference Pathogen-informed resistance breeding based on molecular and evolutionary analysis of the wheat - powdery mildew interaction 27.10.2017 Wuhan, China Keller Beat;
Botanikertagung 2017 - Plant Research in a Changing World, Kiel, Germany Talk given at a conference Invited Keynote Lecture: Molecular and evolutionary analysis of the wheat - powdery mildew interaction 19.09.2017 Kiel, Germany Keller Beat;
6th Powdery Mildew Workshop, Eger, Hungary, 15. September 2017 Talk given at a conference Invited Keynote talk: Molecular evolutionary analysis of the cereal - powdery mildew interactions 15.09.2017 Eger, Hungary Keller Beat;
6th International Powdery Mildew Workshop, Eger, Hungary Talk given at a conference Transcriptomics studies of wheat, rye and triticale powdery mildews identify effectors with potential role in host adaptation 14.09.2017 Eger, Hungary Praz Coraline;
Host-Microbes Genomics Workshop, Neuchatel, Switzerland Talk given at a conference Non parent-of-origin expression of numerous effector genes indicates a role of gene regulation in host adaptation of the hybrid triticale powdery mildew pathogen 08.09.2017 Neuchatel, Switzerland Praz Coraline;
4th International Symposium on Genomics of Plant Genetic Resources, Giessen, Germany Talk given at a conference Invited Keynote Talk: Origin, diversity and evolution of wheat resistance genes: applications in breeding 04.09.2017 Giessen, Germany Keller Beat;
The Sainsbury Laboratory Summer school, Norwich, UK Talk given at a conference Molecular analysis of wheat – fungal pathosystems and applications in resistance breeding 10.08.2017 Norwich, Great Britain and Northern Ireland Keller Beat;
International Wheat Genetics Symposium, Tulln (Vienna), Austria Talk given at a conference Pathogen-informed strategies for wheat resistance improvement 25.04.2017 Tulln, Austria Keller Beat;
13th International Wheat Genetics Symposium, Tulln, Austria Talk given at a conference Rapid gene isolation in barley and wheat by mutant chromosome sequencing 23.04.2017 Tulln, Austria Sanchez Martin Javier;
COST Action Sustain: 4th Annual Conference, Bled, Slovenia Talk given at a conference Host and pathogen-informed strategies to achieve durable resistance in cereals 02.03.2017 Bled, Slovenia Keller Beat;
Swiss Plant Meeting, Leukerbad, Switzerland Talk given at a conference Pathogen-derived proteins recognized by wheat NLR immune receptors 27.01.2017 Leukerbad, Switzerland Keller Beat;
Plant and Animal Genome Meeting, San Diego, USA Talk given at a conference Genomic approaches provide novel tools for rapid cloning of major QTL in large cereal genomes 15.01.2017 San Diego, United States of America Keller Beat;
Wheat Research - Solutions to feed the earth's growing population. Wheat Conference organized by the German Ministry of Food and Agriculture, Frankfurt, Germany Talk given at a conference Genomics-assisted breeding approaches to improve durable fungal resistance in wheat 08.12.2016 Frankfurt, Germany Keller Beat;
Wissenschaftlicher Workshop Agroscope Reckenholz, Zürich, Switzerland Talk given at a conference Weizenforschung an der Universität Zürich 07.12.2016 Zürich, Switzerland Keller Beat;
Réunion Annuelle du Réseau Résistance, organized by INRA, Montpellier, France Talk given at a conference The functional study of the wheat gene Lr34 in heterologous crop species 08.11.2016 Montpellier, France Sucher Justine;
Wheat Initiative: Meeting of the Expert Working Group on control of wheat pests and pathogens, Minneapolis, USA Talk given at a conference Powdery mildew in wheat: a global perspective 04.11.2016 Minneapolis, United States of America Keller Beat;
Achieving durable resistance to wheat diseases and pests. Minneapolis/Bloomington, USA Talk given at a conference Host and pathogen-informed strategies to achieve durable resistance 02.11.2016 Minneapolis/Bloomington, United States of America Keller Beat;
60th Annual Congress Società Italiana Genetica Agraria, Catania, Italy Talk given at a conference Host and pathogen-informed strategies to achieve durable resistance in wheat 13.09.2016 Catania, Italy Keller Beat;
20th EUCARPIA General Congress (European Association for Research on Plant Breeding), Zürich, Switzerland Talk given at a conference Keynote Lecture: Molecular diversity of fungal disease resistance genes in cereals and their applications in breeding 01.09.2016 Zürich, Switzerland Keller Beat;
20th EUCARPIA General Congress, Zurich, Switzerland Talk given at a conference Understanding gain-of-virulence of powdery mildew on triticale using transcriptomics 29.08.2016 Zurich, Switzerland Praz Coraline;
20th EUCARPIA General Congress, Zurich, Switzerland Talk given at a conference Association mapping of durable resistance to wheat powdery mildew 29.08.2016 Zurich, Switzerland Sanchez Martin Javier;
International Powdery Mildew Symposium, IS-MPMI Conference, Portland OR, USA Talk given at a conference Deciphering the molecular basis of race-specific resistance in cereal powdery mildews using a worldwide resolution of sequence diversity and functional analyses 16.07.2016 Portland, Oregon, United States of America Mc Nally Kaitlin;
Invited talk, Leopoldina, Halle, Germany Individual talk Fungal disease resistance in cereal crops 26.05.2016 Halle, Germany Keller Beat;
University of Copenhagen, Invited seminar, Copenhagen, Denmark Individual talk Molecular analysis of cereal crop interactions with fungal pathogens 07.04.2016 Copenhagen, Denmark Keller Beat;
COST Action Sustain: 3rd annual conference, Banyuls, France Talk given at a conference Multiple avirulence loci, allele-specific effector recognition and a pathogen encoded suppressor of avirulence control the Pm3 race-specific resistance of wheat to powdery mildew 17.02.2016 Banyuls, France Bourras Salim;
1st Swiss Wheat Genetics Minisymposium, Bern, Switzerland Talk given at a conference Update on the International Wheat Genome Sequencing Project 28.01.2016 Bern, Switzerland Keller Beat;
Cerealpath Meeting, Dublin, Ireland Talk given at a conference Genetic characterization and high resolution analysis of Lr75, a novel adult plant leaf rust resistance gene in wheat 27.01.2016 Dublin, Ireland Keller Beat;
Zurich Mycology Symposium, WSL Birmensdorf, Switzerland Talk given at a conference Transcriptome analysis of the wheat/wheat powdery mildew interaction 22.01.2016 Birmensdorf, Switzerland Praz Coraline;
Plant and Animal Genome Meeting, San Diego, USA Poster Transcriptome analysis of the wheat/wheat powdery mildew interaction 08.01.2016 San Diego, United States of America Praz Coraline;
Plant and Animal Genome Meeting, San Diego, USA Poster The Functional Transfer of the Wheat Gene Lr34 into Rice and Its Resistance Against Rice Blast 08.01.2016 San Diego, United States of America Sucher Justine;


Knowledge transfer events

Active participation

Title Type of contribution Date Place Persons involved
Jahresendveranstaltung Bundesamt für Landwirtschaft, Bern, Switzerland Talk 18.12.2018 Bern, Switzerland Keller Beat;
Ringvorlesung: Die Domestikation des Lebens; Wie viel Domestikation brauchen unsere Nutzpflanzen? Ernährungssicherung und Züchtungstechniken im Feld und Labor Talk 23.11.2017 Zurich, Switzerland Keller Beat;
The Geneva Association, 13th Annual Liability Conference, Hosted by Zurich Insurance Group, Zurich, Switzerland Talk 09.11.2017 Zurich, Switzerland Keller Beat;
Podiumsdiskussion Verantaltung Swissaid, Bern, Switzerland Talk 10.11.2016 Bern, Switzerland Keller Beat;


Communication with the public

Communication Title Media Place Year
Media relations: radio, television Debatte: Ist das noch Gentechnik – oder darf das auf den Acker? SRF German-speaking Switzerland 2018
Media relations: print media, online media Der Weizenflüsterer Tagesanzeiger German-speaking Switzerland 2018
Media relations: radio, television Echo der Zeit, Wie umgehen mit den neuen Gentech-Methoden? SRF German-speaking Switzerland 2018

Associated projects

Number Title Start Funding scheme
182833 Molecular analysis of disease resistance specificity in cereals 01.01.2019 Project funding
127061 Molecular analysis of both broad-spectrum and specific fungal disease resistance in wheat 01.01.2010 Project funding
144081 Molecular interactions of wheat and fungal pathogens: Lr34-based, durable resistance and the wheat-powdery mildew pathosystem 01.01.2013 Project funding

Abstract

The three cereal crop species wheat, rice and maize directly or indirectly contribute about 50% of the globally consumed calories for humans. Fungal diseases are a major limiting factor in cereal production. There is an enormous natural diversity of disease resistance sources in the gene pool of the three species, but the molecular nature and function of the involved genes is largely unexplored. We want to use some of these resources for improving our mechanistic understanding of different forms of disease resistance providing efficient defense in agro-ecosystems. We propose to study the molecular mechanisms of three resistance types that we have identified in wheat and maize: the wheat genes Lr34 and Lr75 are quantitative resistance genes, the maize Htn1 gene is possibly a damage induced molecular pattern (DAMP) receptor and the Pm3-AvrPm3 interaction is based on an allelic series of R genes interacting with the pathogen in a genetically highly complex way.We have found that the durable wheat resistance gene Lr34 is also functional in the diploid species barley and rice and, therefore, its function in grasses must be based on a widely conserved mechanism. To identify biochemically the substrate of the LR34 transporter, yeast and plant protoplast assays will be used, focusing on the recently identified candidate substrate abscisic acid. Based on the Lr34-induced, senescence-like phenotype observed in N. benthamiana, protein function and localization studies will be done. Lr34 together with Lr75 confer durable leaf rust resistance in winter wheat cultivar Forno. We will clone Lr75 (already well-advanced work in the lab) and functionally study this gene and its interaction with a seedling resistance gene. Our recent isolation of the maize Htn1 gene conferring quantitative, broad-spectrum resistance against Northern Corn Leaf Blight has shown that it encodes a WAK-domain receptor-like kinase, putatively acting as DAMP receptor recognizing degradation products from cell wall attack. We want to identify the ligand of HTN1 by carbohydrate microarray analysis and study protein kinase function, protein localization and the transcriptome network induced by HTN1.For the Pm3-AvrPm3 interaction involving a major resistance (R) gene, we will build on our recent cloning of the first avirulence factor, AvrPm3a/f. Using site-directed mutagenesis and natural diversity analysis, critical R and Avr protein sequences involved in the interaction will be identified. Protein partners interacting with AvrPm3a/f will be isolated by co-immuno-precipitation and yeast-2-hybrid screens. Besides the established N. benthiamana system for functional analysis, we will also test the transformable hemibiotrophic fungal pathogen Zymoseptoria tritici as a novel delivery system. Transcriptomic studies of effector gene expression in several isolates as well as genetic studies will be used for the identification of one or more additional AvrPm3 genes. The genetic network of AvrPm3a/f will be further studied by the molecular isolation of an allele-specific mutant (exp3) at a new genetic locus. This project part should contribute to the development of pathogen-informed strategies in resistance breeding.Finally, we want to continue our work on mildew evolution and the genetics of host specialization of different mildew forms in cereals. This analysis will use genetic crosses between mildews specialized on wheat and triticale/wheat, or on tetraploid wheat and tetraploid/hexaploid wheat. This will allow the genetic mapping of factors relevant for host expansions. Depending on the outcome of these experiments, single genes or QTL will be mapped at high resolution to identify candidate genes underlying host specialization. This work can rely on our advanced genetic and genomic resources in mildew that we developed in the last grant phase. The work proposed in our application is expected to significantly contribute to an improved molecular understanding of agronomically important, fungal disease resistance.
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