The Arabidopsis PEPR pathway couples local and systemic plant immunity

Authors


Abstract

Recognition of microbial challenges leads to enhanced immunity at both the local and systemic levels. In Arabidopsis, EFR and PEPR1/PEPR2 act as the receptor for the bacterial elongation factor EF-Tu (elf18 epitope) and for the endogenous PROPEP-derived Pep epitopes, respectively. The PEPR pathway has been described to mediate defence signalling following microbial recognition. Here we show that PROPEP2/PROPEP3 induction upon pathogen challenges is robust against jasmonate, salicylate, or ethylene dysfunction. Comparative transcriptome profiling between Pep2- and elf18-treated plants points to co-activation of otherwise antagonistic jasmonate- and salicylate-mediated immune branches as a key output of PEPR signalling. Accordingly, as well as basal defences against hemibiotrophic pathogens, systemic immunity is reduced in pepr1 pepr2 plants. Remarkably, PROPEP2/PROPEP3 induction is essentially restricted to the pathogen challenge sites during pathogen-induced systemic immunity. Localized Pep application activates genetically separable jasmonate and salicylate branches in systemic leaves without significant PROPEP2/PROPEP3 induction. Our results suggest that local PEPR activation provides a critical step in connecting local to systemic immunity by reinforcing separate defence signalling pathways.

Synopsis

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Local microbial recognition involving PEPR pattern recognition receptors leads to a systemic immune response via the Salicylate and Jasmonate hormone signaling pathways.

  • Genome-wide profiling for Pep2-responsive genes in Arabidopsis thaliana shows co-activation of salicylate (SA)- and jasmonate (JA) pathways as an important output of PEPR-mediated signalling.
  • Molecular genetic studies indicate a critical role for PEPRs in pathogen- and microbial pattern-induced systemic immunity.
  • Activation of a PEPR-PROPEP feedback loop is restricted to the pathogen-challenged sites during pathogen-induced systemic immunity.
  • Exogenous application of Pep peptides confers systemic immunity through distinct defence signalling branches.

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