Subfamily C7 Raf-like kinases MRK1, RAF26, and RAF39 regulate immune homeostasis and stomatal opening in Arabidopsis thaliana

Márcia Gonçalves Dias, Bassem Doss, Anamika Rawat, Kristen R. Siegel, Tharika Mahathanthrige, Jan Sklenar, Maria Camila Rodriguez Gallo, Paul Derbyshire, Thakshila Dharmasena, Emma Cameron, R. Glen Uhrig, Cyril Zipfel, Frank L. H. Menke, Jacqueline Monaghan

Research output: Contribution to journalArticlepeer-review

Abstract

The calcium-dependent protein kinase CPK28 regulates several stress pathways in multiple plant species. Here, we aimed to discover CPK28-associated proteins in Arabidopsis thaliana. We used affinity-based proteomics and identified several potential CPK28 binding partners, including the C7 Raf-like kinases MRK1, RAF26, and RAF39. We used biochemistry, genetics, and physiological assays to gain insight into their function. We define redundant roles for these kinases in stomatal opening, immune-triggered reactive oxygen species (ROS) production, and resistance to a bacterial pathogen. We report that CPK28 associates with and trans-phosphorylates RAF26 and RAF39, and that MRK1, RAF26, and RAF39 are active kinases that localize to endomembranes. Although Raf-like kinases share some features with mitogen-activated protein kinase kinase kinases (MKKKs), we found that MRK1, RAF26, and RAF39 are unable to trans-phosphorylate any of the 10 Arabidopsis mitogen-activated protein kinase kinases (MKKs). Overall, our study suggests that C7 Raf-like kinases associate with and are phosphorylated by CPK28, function redundantly in stomatal opening and immunity, and possess substrate specificities distinct from canonical MKKKs.

Original languageEnglish
Pages (from-to)2278-2294
Number of pages17
JournalNew Phytologist
Volume244
Issue number6
Early online date24 Oct 2024
DOIs
Publication statusPublished - Dec 2024

Keywords

  • Arabidopsis thaliana
  • C7 Raf-like kinase
  • CPK28
  • immunity
  • MRK1
  • RAF26
  • RAF39
  • stomata

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