Early changes in the Arabidopsis thaliana membrane phosphoproteome in response
to oligogalacturonides (OGs), a class of plant damage-associated molecular patterns
(DAMPs), were analyzed by two complementary proteomic approaches. Differentially
phosphorylated sites were determined through phosphopeptide enrichment followed
by LC-MS/MS using label-free quantification; differentially phosphorylated proteins
were identified by 2D-DIGE combined with phospho-specific fluorescent staining
(phospho-DIGE). This large-scale phosphoproteome analysis of early OG-signaling
enabled us to determine 100 regulated phosphosites using LC-MS/MS and 46
differential spots corresponding to 34 pdhosphoproteins using phospho-DIGE.
Functional classification showed that the OG-responsive phosphoproteins include
kinases, phosphatases and receptor-like kinases, heat shock proteins (HSPs), reactive
oxygen species (ROS) scavenging enzymes, proteins related to cellular trafficking,
transport, defense and signaling as well as novel candidates for a role in immunity,
for which elicitor-induced phosphorylation changes have not been shown before. A
comparison with previously identified elicitor-regulated phosphosites shows only a very
limited overlap, uncovering the immune-related regulation of 70 phosphorylation sites
and revealing novel potential players in the regulation of elicitor-dependent immunity.