GRIM REAPER peptide binds to receptor kinase PRK 5 to trigger cell death in Arabidopsis

Abstract

Recognition of extracellular peptides by plasma membranelocalized receptor proteins is commonly used in signal transduction. In plants, very little is known about how extracellular peptides are processed and activated in order to allow recognition by receptors. Here, we show that induction of cell death in planta by a secreted plant protein GRIM REAPER (GRI) is dependent on the activity of the type II metacaspase METACASPASE-9. GRI is cleaved by METACASPASE-9 in vitro resulting in the release of an 11 amino acid peptide. This peptide bound in vivo to the extracellular domain of the plasma membrane-localized, atypical leucine-rich repeat receptorlike kinase POLLEN-SPECIFIC RECEPTOR-LIKE KINASE 5 (PRK5) and was sufficient to induce oxidative stress/ROS-dependent cell death. This shows a signaling pathway in plants from processing and activation of an extracellular protein to recognition by its receptor.

The Plant Peptidome: An Expanding Repertoire of Structural Features and Biological Functions

“…A diverse group of plant peptides is not characterized by specific PTMs, such as Pro hydroxylation and glycosylation and/or Tyr sulfation, or the presence of two or more Cys, though we do not exclude the possibility that any of these PTMs could be detected in the future (Pearce et al, 1991;Huffaker et al, 2006;Wrzaczek et al, 2015). These "non-Cys-rich/non-PTM peptides" can contain functionally important amino acids in their primary structure such as Pro, Gly, and Lys and are mainly released from a proprotein (Figures 1 and 3) (Constabel et al, 1995;Huffaker et al, 2006;Wrzaczek et al, 2015).…”

“…These "non-Cys-rich/non-PTM peptides" can contain functionally important amino acids in their primary structure such as Pro, Gly, and Lys and are mainly released from a proprotein (Figures 1 and 3) (Constabel et al, 1995;Huffaker et al, 2006;Wrzaczek et al, 2015). They are 8 to 36 amino acids in length and have reported roles mainly in the defense response of plants (Figure 2).…”

“…Recently, GRIM REAPER PEPTIDE (GRIp) was identified in Arabidopsis as a novel, basic Lys-rich 11-amino acid peptide with homologs in crucifers (Wrzaczek et al, 2015) (Figure 3). The formation of GRIp from the preproprotein GRI is unique because this is the first report in plants of a specific type of protease, METACASPASE-9, involved in the release of a mature functional peptide.…”

An Allelic Series of bak1 Mutations Differentially Alter bir1 Cell Death, Immune Response, Growth, and Root Development Phenotypes in Arabidopsis thaliana

“…Prior studies have hypothesized that BAK1/BKK1 may function redundantly as coreceptors for an as yet unidentified RLK or RLKs controlling cell death, similar to the role of BAK1 in PTI and BR signaling pathways ). The PRK5 LRR-RLK has been found recently to bind the GRIM REAPER cell deathinducing peptide (Wrzaczek et al 2015) and is one candidate RLK that may interact with BAK1/BKK1, but this interaction has not been tested yet.A role for SERK receptors in root development has been described recently Gou et al 2012). Formation of the cell layers and distinct cell types of the primary root occurs through oriented cell divisions in the root apical meristem (RAM) at the tip of the root.…”

“…Prior studies have hypothesized that BAK1/BKK1 may function redundantly as coreceptors for an as yet unidentified RLK or RLKs controlling cell death, similar to the role of BAK1 in PTI and BR signaling pathways ). The PRK5 LRR-RLK has been found recently to bind the GRIM REAPER cell deathinducing peptide (Wrzaczek et al 2015) and is one candidate RLK that may interact with BAK1/BKK1, but this interaction has not been tested yet.…”