Differential Protein Phosphorylation Regulates Chloroplast Movement in Response to Strong Light and Darkness in Arabidopsis thaliana

Mature pollen represents an extremely resistant quiescent structure surrounded by a tough cell wall. After its hydration on stigma papillary cells, pollen tube growth starts rapidly. Massive metabolic changes are likely to be accompanied by changes in protein phosphorylation. Protein phosphorylation belongs among the most rapid post-translational modifications. To date, only Arabidopsis thaliana and tobacco (Nicotiana tabacum) mature pollen have been subjected to phosphoproteomic studies in order to identify the phosphoproteins present. In the present mini-review, Arabidopsis and tobacco datasets were compared with each other. The representation of the O-phosphorylated amino acids was compared between these two datasets, and the putative pollen-specific or pollen-abundant phosphopeptides were highlighted. Finally, the phosphorylation sites common for both Arabidopsis and tobacco phosphoproteins are listed as well as the phosphorylation motifs identified.

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The plasma membrane-associated Ca2+- binding protein PCaP1 is required for oligogalacturonide and flagellin-induced priming and immunity

10.22541/au.161821112.26916822/v1 ◽

2021 ◽

Author(s):

Moira Giovannoni ◽

Lucia Marti ◽

Simone Ferrari ◽

Natsuki Tanaka-Takada ◽

Masayoshi Maeshima ◽

...

Keyword(s):

Immune Response ◽

Arabidopsis Thaliana ◽

Plasma Membrane ◽

Membrane Proteins ◽

Protein Phosphorylation ◽

Wild Type ◽

Reversible Protein Phosphorylation ◽

Endocytic Vesicles ◽

Molecular Patterns ◽

Damage Associated Molecular Patterns

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.

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