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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. The Plant Journal, 104(1):200-214.

Abstract

The development of improved plant nucleotide-binding, leucine-rich repeat (LRR) immune receptors (NLRs) has mostly been based on random mutagenesis or on structural information available for specific receptors complexed with the recognized pathogen effector. Here, we use a targeted mutagenesis approach based on the natural diversity of the Pm3 powdery mildew resistance alleles present in different wheat (Triticum aestivum) genotypes. In order to understand the functional importance of the amino acid polymorphisms between the active immune receptor PM3A and the inactive ancestral variant PM3CS, we exchanged polymorphic regions and residues in the LRR domain of PM3A with the corresponding segments of PM3CS. These novel variants were functionally tested for recognition of the corresponding AVRPM3A2/F2 avirulence protein in Nicotiana benthamiana. We identified polymorphic residues in four regions of PM3A that enhance the immune response, but also residues that reduce it or result in complete loss of function. We found that the identified critical residues in PM3A modify its activation threshold towards different protein variants of AVRPM3A2/F2 . PM3A variants with a lowered threshold gave a stronger overall response and gained an extended recognition spectrum. One of these variant proteins with a single amino acid change was stably transformed into wheat, where it conferred race-specific resistance to mildew. This is a proof of concept that improved PM3A variants with an enlarged recognition spectrum can be engineered based on natural diversity by exchanging single or multiple residues that modulate resistance function.

Abstract

The development of improved plant nucleotide-binding, leucine-rich repeat (LRR) immune receptors (NLRs) has mostly been based on random mutagenesis or on structural information available for specific receptors complexed with the recognized pathogen effector. Here, we use a targeted mutagenesis approach based on the natural diversity of the Pm3 powdery mildew resistance alleles present in different wheat (Triticum aestivum) genotypes. In order to understand the functional importance of the amino acid polymorphisms between the active immune receptor PM3A and the inactive ancestral variant PM3CS, we exchanged polymorphic regions and residues in the LRR domain of PM3A with the corresponding segments of PM3CS. These novel variants were functionally tested for recognition of the corresponding AVRPM3A2/F2 avirulence protein in Nicotiana benthamiana. We identified polymorphic residues in four regions of PM3A that enhance the immune response, but also residues that reduce it or result in complete loss of function. We found that the identified critical residues in PM3A modify its activation threshold towards different protein variants of AVRPM3A2/F2 . PM3A variants with a lowered threshold gave a stronger overall response and gained an extended recognition spectrum. One of these variant proteins with a single amino acid change was stably transformed into wheat, where it conferred race-specific resistance to mildew. This is a proof of concept that improved PM3A variants with an enlarged recognition spectrum can be engineered based on natural diversity by exchanging single or multiple residues that modulate resistance function.

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Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Pharmacology and Toxicology
07 Faculty of Science > Institute of Pharmacology and Toxicology

07 Faculty of Science > Department of Plant and Microbial Biology
07 Faculty of Science > Zurich-Basel Plant Science Center
08 Research Priority Programs > Evolution in Action: From Genomes to Ecosystems
Dewey Decimal Classification:580 Plants (Botany)
Scopus Subject Areas:Life Sciences > Genetics
Life Sciences > Plant Science
Life Sciences > Cell Biology
Uncontrolled Keywords:Plant Science, Genetics, Cell Biology
Language:English
Date:1 September 2020
Deposited On:25 Jan 2021 15:38
Last Modified:24 Jun 2024 01:44
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0960-7412
OA Status:Green
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1111/tpj.14917
PubMed ID:32645755