Abstract
Early signalling events in response to elicitation include reversible protein phosphorylation and re‐localization of plasma membrane (PM) proteins. Oligogalacturonides (OGs) are a class of damage‐associated molecular patterns (DAMPs) that act as endogenous signals to activate the plant immune response. Previous data on early phosphoproteome changes in Arabidopsis thaliana upon OG perception uncovered the immune‐related phospho‐regulation of several membrane proteins, among which PCaP1, a PM‐anchored protein with actin filament–severing activity, was chosen for its potential involvement in OG‐ and flagellin‐triggered responses. Here, we demonstrate that PCaP1 is required for late, but not early, responses induced by OGs and flagellin. Moreover, pcap1 mutants, unlike the wild type, are impaired in the recovery of full responsiveness to a second treatment with OGs performed 24 h after the first one. Localization studies on PCaP1 upon OG treatment in plants expressing a functional PCaP1‐GFP fusion under the control of PCaP1 promoter revealed fluorescence on the PM, organized in densely packed punctate structures, previously reported as microdomains. Fluorescence was found to be associated also with endocytic vesicles, the number of which rapidly increased after OG treatment, suggesting both an endocytic turnover of PCaP1 for maintaining its homeostasis at the PM and an OG‐induced endocytosis.
Highlights
Plants evolved various mechanisms to counteract pathogen attacks
Plasma membrane Cation Binding Protein 1 (PCaP1) is required for OG-induced priming The identification of PCaP1 among the membrane proteins differentially phosphorylated within 10 min after treatment with OGs suggested its possible involvement in OG-triggered immunity
To analyse the priming response in pcap1 mutants, adult plants were sprayed with OGs, flg22 or water and leaves were inoculated with B. cinerea spores 24 h after the treatment
Summary
Plants evolved various mechanisms to counteract pathogen attacks. Some of these provide constitutive physical and chemical barriers to pathogen infections while others are induced only upon pathogen perception (Boller & Felix, 2009). Pathogen-/microbe-associated molecular patterns (PAMPs/MAMPs) are conserved molecules secreted or present on the surface of microbial pathogens that are capable of activating the so-called pattern-triggered immunity (PTI) against a wide range of pathogens. Plants are capable of activating the immune system by sensing endogenous molecular patterns present only when the tissue is infected or damaged (damageassociated molecular patterns or DAMPs), discriminating between an intact and an altered self (Duran-Flores & Heil, 2018; Hou et al, 2019). OGs act as DAMPs and as negative regulators of plant growth and development mainly through their antagonism with auxin (Bellincampi et al, 1993; Ferrari et al, 2013; Pontiggia et al, 2020; Savatin et al, 2011)
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