Comparing Arabidopsis receptor kinase and receptor protein-mediated immune signaling reveals BIK1-dependent differences

New Phytol. 2019 Mar;221(4):2080-2095. doi: 10.1111/nph.15497. Epub 2018 Oct 25.


Pattern recognition receptors (PRRs) sense microbial patterns and activate innate immunity against attempted microbial invasions. The leucine-rich repeat receptor kinases (LRR-RK) FLS2 and EFR, and the LRR receptor protein (LRR-RP) receptors RLP23 and RLP42, respectively, represent prototypical members of these two prominent and closely related PRR families. We conducted a survey of Arabidopsis thaliana immune signaling mediated by these receptors to address the question of commonalities and differences between LRR-RK and LRR-RP signaling. Quantitative differences in timing and amplitude were observed for several early immune responses, with RP-mediated responses typically being slower and more prolonged than those mediated by RKs. Activation of RLP23, but not FLS2, induced the production of camalexin. Transcriptomic analysis revealed that RLP23-regulated genes represent only a fraction of those genes differentially expressed upon FLS2 activation. Several positive and negative regulators of FLS2-signaling play similar roles in RLP23 signaling. Intriguingly, the cytoplasmic receptor kinase BIK1, a positive regulator of RK signaling, acts as a negative regulator of RP-type immune receptors in a manner dependent on BIK1 kinase activity. Our study unveiled unexpected differences in two closely related receptor systems and reports a new negative role of BIK1 in plant immunity.

Keywords: Arabidopsis; immune receptor; immune signaling comparison; plant immunity; receptor kinase; receptor protein.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis Proteins / metabolism*
  • Flagellin / pharmacology
  • Genotype
  • Peptides / pharmacology
  • Phosphorylation
  • Plant Growth Regulators / biosynthesis
  • Plant Immunity* / drug effects
  • Protein Kinases / metabolism*
  • Protein Serine-Threonine Kinases / metabolism*
  • Reactive Oxygen Species / metabolism
  • Receptors, Pattern Recognition / metabolism*
  • Salicylic Acid / pharmacology
  • Sesquiterpenes / metabolism
  • Signal Transduction* / drug effects
  • Transcription, Genetic / drug effects


  • Arabidopsis Proteins
  • Peptides
  • Plant Growth Regulators
  • Reactive Oxygen Species
  • Receptors, Pattern Recognition
  • Sesquiterpenes
  • Flagellin
  • phytoalexins
  • Protein Kinases
  • BIK1 protein, Arabidopsis
  • Protein Serine-Threonine Kinases
  • Salicylic Acid