Constitutive Activation of Leucine-Rich Repeat Receptor Kinase Signaling Pathways by BAK1-INTERACTING RECEPTOR-LIKE KINASE3 Chimera

Plant Cell. 2020 Oct;32(10):3311-3323. doi: 10.1105/tpc.20.00138. Epub 2020 Aug 13.


Receptor kinases with extracellular leucine-rich repeat domains (LRR-RKs) form the largest group of membrane signaling proteins in plants. LRR-RKs can sense small molecule, peptide, or protein ligands and may be activated by ligand-induced interaction with a shape complementary SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) coreceptor kinase. We have previously shown that SERKs can also form constitutive, ligand-independent complexes with the LRR ectodomains of BAK1-INTERACTING RECEPTOR-LIKE KINASE3 (BIR3) receptor pseudokinases, negative regulators of LRR-RK signaling. Here, we report that receptor chimera in which the extracellular LRR domain of BIR3 is fused to the cytoplasmic kinase domains of the SERK-dependent LRR-RKs BRASSINOSTEROID INSENSITIVE1, HAESA and ERECTA form tight complexes with endogenous SERK coreceptors in the absence of ligand stimulus. Expression of these chimeras under the control of the endogenous promoter of the respective LRR-RK leads to strong gain-of-function brassinosteroid, floral abscission, and stomatal patterning phenotypes, respectively. Importantly, a BIR3-GASSHO1 (GSO1)/SCHENGEN3 (SGN3) chimera can partially complement sgn3 Casparian strip formation phenotypes, suggesting that SERK proteins also mediate GSO1/SGN3 receptor activation. Collectively, our protein engineering approach may be used to elucidate the physiological functions of orphan LRR-RKs and to identify their receptor activation mechanism in single transgenic lines.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • DNA-Binding Proteins / metabolism
  • Gene Expression Regulation, Plant
  • Hypocotyl / genetics
  • Hypocotyl / growth & development
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Plants, Genetically Modified
  • Protein Domains
  • Protein Kinases / genetics
  • Protein Kinases / metabolism*
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction*


  • Arabidopsis Proteins
  • BES1 protein, Arabidopsis
  • DNA-Binding Proteins
  • Membrane Proteins
  • Recombinant Fusion Proteins
  • Protein Kinases
  • GASSHO1 protein, Arabidopsis
  • SERK1 protein, Arabidopsis
  • BRI1 protein, Arabidopsis
  • Bir3 protein, Arabidopsis
  • Protein Serine-Threonine Kinases