The Arabidopsis pattern recognition receptor EFR enhances fire blight resistance in apple

Stefano Piazza,Vladimir Nekrasov,Valerio Pompili,Lorenza Dalla Costa,Cyril Zipfel,Mickael Malnoy,Manuela Campa,Umberto Salvagnin

doi:10.1038/s41438-021-00639-3

Abstract

Fire blight disease, caused by the bacterium Erwinia amylovora (E. amylovora), is responsible for substantial losses in cultivated apples worldwide. An important mechanism of plant immunity is based on the recognition of conserved microbial molecules, named pathogen-associated or microbe-associated molecular patterns (PAMPs or MAMPs), through pattern recognition receptors (PRRs), leading to pattern-triggered immunity (PTI). The interspecies transfer of PRRs represents a promising strategy to engineer broad-spectrum and durable disease resistance in crops. EFR, the Arabidopsis thaliana PRR for the PAMP elf18 derived from the elongation factor thermal unstable (EF-Tu) proved to be effective in improving bacterial resistance when expressed into Solanaceae and other plant species. In this study, we tested whether EFR can affect the interaction of apple with E. amylovora by its ectopic expression in the susceptible apple rootstock M.26. Stable EFR expression led to the activation of PAMP-triggered immune response in apple leaves upon treatment with supernatant of E. amylovora, as measured by the production of reactive oxygen species and the induction of known defense genes. The amount of tissue necrosis associated with E. amylovora infection was significantly reduced in the EFR transgenic rootstock compared to the wild-type. Our results show that the expression of EFR in apple rootstock may be a valuable biotechnology strategy to improve the resistance of apple to fire blight.

Highlights

Despite being constantly exposed to a wide range of pathogens in their immediate environment, plants are resistant to most microbes
Evaluation of E. amylovora elongation factor thermal unstable (EF-Tu) eliciting activity Based on the EF-Tu sequence from Escherichia coli
To verify the activity of E. amylovora EF-Tu elicitor, heat-killed E. amylovora extracts were applied to wildtype and efr mutant A. thaliana leaf discs

Summary

Introduction

Despite being constantly exposed to a wide range of pathogens in their immediate environment, plants are resistant to most microbes. Each plant cell can trigger an immune response autonomously by employing pattern recognition receptors (PRRs) for sensitive and rapid detection of potential threats caused by pests or pathogens[1]. This mechanism is based on the recognition of conserved microbial molecules (pathogen-associated or microbial-associated molecular patterns, PAMPs or MAMPs) and is known as pattern-triggered immunity (PTI). Arabidopsis recognizes the Nterminus of the protein and the N-acetylated peptide comprising the first 18 amino acids of EF-Tu, called elf[18]. EF-Tu is recognized by EF-TU RECEPTOR (EFR), a Brassicaceae-specific[10].

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