Early signaling 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- as well as
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.
The ESCRT-III-Interacting Deubiquitinating Enzyme AMSH3 is Essential for Degradation of Ubiquitinated Membrane Proteins in Arabidopsis thaliana