BIK1 interacts with PEPRs to mediate ethylene-induced immunity

Proc Natl Acad Sci U S A. 2013 Apr 9;110(15):6205-10. doi: 10.1073/pnas.1215543110. Epub 2013 Feb 19.

Abstract

Plants have evolved intricate immune mechanisms to combat pathogen infection. Upon perception of pathogen-derived signals, plants accumulate defense hormones such as ethylene (ET), jasmonate, salicylate, and damage-associated molecular patterns to amplify immune responses. In particular, the Arabidopsis peptide Pep1 and its family members are thought to be damage-associated molecular patterns that trigger immunity through Pep1 receptor kinases PEPR1 and PEPR2. Here we show that PEPR1 specifically interacts with receptor-like cytoplasmic kinases botrytis-induced kinase 1 (BIK1) and PBS1-like 1 (PBL1) to mediate Pep1-induced defenses. In vitro and in vivo studies suggested that PEPR1, and likely PEPR2, directly phosphorylates BIK1 in response to Pep1 treatment. Surprisingly, the pepr1/pepr2 double-mutant seedlings displayed reduced in sensitivity to ET, as indicated by the elongated hypocotyls. ET-induced expression of defense genes and resistance to Botrytis cinerea were compromised in pepr1/pepr2 and bik1 mutants, reenforcing an important role of PEPRs and BIK1 in ET-mediated defense signaling. Pep treatment partially mimicked ET-induced seedling growth inhibition in a PEPR- and BIK1-dependent manner. Furthermore, both ET and Pep1 treatments induced BIK1 phosphorylation in a PEPR-dependent manner. However, the Pep1-induced BIK1 phosphorylation, seedling growth inhibition, and defense gene expression were independent of canonical ET signaling components. Together our results illustrate a mechanism by which ET and PEPR signaling pathways act in concert to amplify immune responses.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / immunology*
  • Arabidopsis Proteins / metabolism*
  • DNA, Complementary / metabolism
  • Disease Resistance
  • Ethylenes / pharmacology*
  • Genes, Reporter
  • Mutation
  • Phosphorylation
  • Plant Growth Regulators / pharmacology
  • Plant Immunity*
  • Protein Interaction Domains and Motifs
  • Protein Serine-Threonine Kinases / metabolism*
  • Receptors, Cell Surface / metabolism*
  • Respiratory Burst
  • Signal Transduction
  • Two-Hybrid System Techniques

Substances

  • Arabidopsis Proteins
  • DNA, Complementary
  • Ethylenes
  • PEPR1 protein, Arabidopsis
  • Plant Growth Regulators
  • Receptors, Cell Surface
  • ethylene
  • BIK1 protein, Arabidopsis
  • PEPR2 protein, Arabidopsis
  • Protein Serine-Threonine Kinases