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Functional analysis of host-specific disease resistance in wheat

English title Functional analysis of host-specific disease resistance in wheat
Applicant Keller Beat
Number 204165
Funding scheme Project funding (Div. I-III)
Research institution Institut für Pflanzen- und Mikrobiologie Universität Zürich
Institution of higher education University of Zurich - ZH
Main discipline Molecular Biology
Start/End 01.01.2022 - 31.01.2025
Approved amount 923'047.00
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All Disciplines (4)

Discipline
Molecular Biology
Genetics
Botany
Agricultural and Forestry Sciences

Keywords (8)

leaf rust; avirulence gene; resistance gene; wheat; pathogen genomics; powdery mildew ; host specificity; host pathogen interaction

Lay Summary (German)

Lead
Weizen wird von pilzlichen Krankheitserregern befallen, die weltweit zu grossen Ertragsausfällen führen. Wir haben kürzlich in Weizen drei Gene identifiziert, die Resistenz gegen die Pathogene Braunrost und Mehltau vermitteln. Diese Gene bilden neuartige Typen von Immunrezeptoren. Im vorliegenden Projekt wollen wir deren Funktionsweise untersuchen.
Lay summary
Inhalt und Ziele des Forschungsprojekts

Die natürlicherweise vorkommenden Resistenzgene in einigen wenigen Weizenlinien sind züchterisch von grosser Bedeutung für die Entwicklung resistenter Weizensorten. Die von uns kürzlich identifizierten Resistenzgene sind molekular unterschiedlich zu bisher bekannten Genen. Die Funktionsweisen dieser neuen Formen von Resistenz sind auf molekularer Ebene nicht verstanden.

Das Projekt widmet sich darum der Frage, wie Weizen mit den neuartigen Immunrezeptoren die Anwesenheit von pilzlichen Pathogenen erkennen und dadurch Abwehrreaktionen auslösen kann. Das vorliegende Projekt wird zum Verständnis der pflanzlichen Erkennungsmechanismen von Krankheitserregern beitragen. Die neuen Wirkungsmechanismen sollen verglichen werden mit der molekularen Funktion der klassischen, gut bekannten Immunrezeptoren. Zudem wollen wir Strategien zur effizienten Isolation weiterer Resistenzgene aus Weizen entwickeln. Damit wollen wir die Vielfalt von Resistenzmechanismen erforschen.

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Das Projekt beschäftigt sich mit Krankheitsresistenz von Weizen und leistet einen Beitrag zu global relevanten Forschungsfragen. Da Pflanzenkrankheiten und ihre Bekämpfung, z.B. mit chemischen Hilfsstoffen, ökonomisch wie ökologisch von grosser Bedeutung sind, steht diese Forschungsrichtung auch im Brennpunkt gesellschaftlicher Aufmerksamkeit.

Direct link to Lay Summary Last update: 29.09.2021

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
192526 Field studies of transgenic cereal crops containing heterologous, modified or combined resistance genes against fungal pathogens 01.04.2020 Project funding (Div. I-III)
182833 Molecular analysis of disease resistance specificity in cereals 01.01.2019 Project funding (Div. I-III)

Abstract

Genetic resistance against plant pathogens is an economically and ecologically sustainable way to fight crop plant diseases. In race-specific host resistance a single gene in the host recognizes a single avirulence gene in the pathogen, resulting in defense induction. Isolates (historically called races) of a pathogen species differ in avirulence gene content and, therefore, the observed resistance is isolate-dependent and follows a gene-for-gene interaction. At the biochemical level, it was found that avirulence genes frequently encode effector proteins recognized by plant immune receptors, resulting in the induction of defense responses and effector-triggered immunity. Many race-specific resistance genes encode immune receptors of the nucleotide-binding leucine-rich repeat (NLR) structure. We recently (published in 2021) identified three new, race-specific resistance genes in wheat: Pm4a/b and WTK4 against powdery mildew (Pm) and Lr14a against leaf rust (Lr). Pm4 and Lr14a encode a serine-threonine kinase/multiple C2-domains and transmembrane region chimeric protein and an ankyrin-repeat transmembrane domain protein, respectively. Such proteins have previously not been implicated in race-specific resistance, providing a rich resource for the discovery of novel molecular mechanisms underlying race-specific immunity. Furthermore, WTK4 encodes a tandem kinase and belongs to a small (5) group of genes recently found to confer resistance to several diseases in wheat and barley, with an unknown molecular mechanism. Here, we want to study the function of these novel immune receptors with a focus on their biochemical and genetic interactions with other proteins and modifier genes. The work includes the identification of the matching avirulence genes (Avr) in the pathogen: AvrPm4a,b, AvrWTK4 and AvrLr14a. For the work on mildew Avr genes we can build on genetic and genomic resources that we previously established for the powdery mildew pathogen: these include a genetic mapping population, three high-quality reference genomes and a global isolate collection. Genetic mapping, GWAS and large-scale screening of candidates will be used to identify the Avr genes.Furthermore, we want to expand on the molecular study of avirulence genes matching a set of NLR encoding genes earlier identified in our lab: Pm2 as well as Pm3 alleles in wheat and Pm3 orthologs in rye (Pm8/Pm17). Identification of AvrPm8 and AvrPm3e from mildew will complete a unique set of NLR/Avr matching proteins and allow us to study the determinants of molecular specificity on both host and pathogen molecules. We also want to identify the host cell targets of AvrPm2 and AvrPm3b mildew effectors and determine their function in pathogenesis. Mutagenesis in mildew will be used to identify additional proteins involved in Pm3/AvrPm3 recognition to add to a comprehensive view on the pathogen factors (in additions to Avr’s) playing a role in the interaction (the wheat-mildew “interactome”). The proposed work will result in novel insights into the molecular basis of race-specific resistance in wheat and the discovery of fundamentally new mechanisms how plants can detect the presence of pathogens. Race-specific resistance genes have been essential resources for breeding worldwide, but pathogens can frequently adapt and evolve virulence. Therefore, the identification of novel types of genes and their mode of action is relevant to develop improved breeding strategies. Thus, we expect that the results will be relevant for breeding as well as agriculture and will represent a contribution to the international effort to build a comprehensive atlas of wheat resistance genes and their matching effectors for the major wheat diseases.
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