Protein Phosphorylation and Dephosphorylation in Plant Immune Signaling Systems - PAMP Signals in Plant Innate Immunity: Signal Perception and Transduction - page 397

9.17 Dephosphorylation Induced by Phosphatases May

Negatively Regulate Innate Immune Responses

Dephosphorylation may also be involved in defense signaling. CESA1 and
CESA3 are two cellulose synthase proteins detected in A. thaliana and both of
them were dephosphorylated in response to elicitor treatment (Benschop et al.
2007 ). A reduction in CESA3 levels or CESA3 activity was shown to induce JA
and ethylene accumulation and invoke defense gene expression in A. thaliana
(Ellis et al. 2002 ; Cano-Delgado et al. 2003 ). Staurosporine, a protein kinase
inhibitor, inhibited Ca 2+ uptake, extracellular alkalinization, ROS production,
and protein phosphorylation induced by an elicitor in tobacco (Lecourieux-
Ouaked et al. 2000 ). In contrast, calyculin A, a protein phosphatase inhibitor
triggered all the above effects. Protein phosphatase inhibitors calyculin A and
okadaic acid stimulated the inducible defenses in the absence of elicitors. The
results suggest that continuous phosphorylation of proteins may occur in the
non-elicited cells and the inhibition of dephosphorylation may be suffi cient to
initiate signal transduction (Lecourieux-Ouaked et al. 2000 ). Phosphatase may
negatively regulate protein kinase in the signaling system. Phosphatases may
function as negative regulators in defense signaling system (Lecourieux-Ouaked
et al. 2000 ) .

References

Anthony RG, Henriques R, Helfer A, Meszaros T, Rios G, Testerink C, Munnik T, Deak M, Koncz
C, Rogre L (2004) A protein kinase target of a PDK1 signalling pathway is involved in root hair
growth in Arabidopsis . EMBO J 23:572-581
Anthony RG, Khan S, Costa J, Pais MS, Bögre L (2006) The Arabidopsis protein kinase PTI1-2 is
activated by convergent phosphatidic acid and oxidative stress signaling pathways downstream
of PDK1 and OXI1. J Biol Chem 281:37536-37546
Asai T, Tena G, Plotnikova J, Willmann MR, Chiu W-L, Gómez-Gómez L, Boller T, Ausubel FM,
Sheen J (2002) MAP kinase signalling cascade in Arabidopsis innate immunity. Nature
415:977-983
Assad FF, Qiu JL, Youngs H, Ehrhardt D, Zimmerli L, Kalde M, Wanner G, Peck SC, Edwards H,
Ramonell K, Somerville CR, Thordal-Christensen H (2004) The PEN1 syntaxin defi nes a novel
cellular compartment upon fungal attack and is required for the timely assembly of papillae. Mol
Biol Cell 15:5118-5129
Benschop JJ, Mohammed S, O'Flaherty M, Heck AJR, Slijper M, Menke FLH (2007)
Quantitative phosphoproteomics of early elicitor signaling in Arabidopsis . Mol Cell
Proteomics 6:1198-1214
Blumwald E, Aharon GS, Lam BC-H (1998) Early signal transduction pathways in plant-pathogen
interactions. Trends Plant Sci 3:342-346
Boudsocq M, Willmann MR, McCormack M, Lee H, Shan L, He P, Bush J, Cheng SH, Sheen J
(2010) Differential innate immune signalling via Ca 2+ sensor protein kinases. Nature
464:418-422
Brodersen P, Petersen M, Bjorn Nielsen H, Zhu S, Newman MA, Shokat KM, Rietz S, Parker J,
Mundy J (2006) Arabidopsis MAP kinase 4 regulates salicylic acid- and jasmonic acid/
ethylene-dependent responses via EDS1 and PAD4. Plant J 47:532-546