title: Stress-induced protein phosphatase 2C is a negative regulator of a mitogen-activated protein kinase.
abstract: Protein phosphatases of type 2C (PP2Cs) play important roles in eukaryotic signal transduction. In contrast to other eukaryotes, plants such as Arabidopsis have an unusually large group of 69 different PP2C genes. At present, little is known about the functions and substrates of plant PP2Cs. We have previously shown that MP2C, a wound-induced alfalfa PP2C, is a negative regulator of mitogen-activated protein kinase (MAPK) pathways in yeast and plants. In this report, we provide evidence that alfalfa salt stress-inducible MAPK (SIMK) and stress-activated MAPK (SAMK) are activated by wounding and that MP2C is a MAPK phosphatase that directly inactivates SIMK but not the wound-activated MAPK, SAMK. SIMK is inactivated through threonine dephosphorylation of the pTEpY motif, which is essential for MAPK activity. Mutant analysis indicated that inactivation of SIMK depends on the catalytic activity of MP2C. A comparison of MP2C with two other PP2Cs, ABI2 and AtP2CHA, revealed that although all three phosphatases have similar activities toward casein as a substrate, only MP2C is able to dephosphorylate and inactivate SIMK. In agreement with the notion that MP2C interacts directly with SIMK, the MAPK was identified as an interacting partner of MP2C in a yeast two-hybrid screen. MP2C can be immunoprecipitated with SIMK in a complex in vivo and shows direct binding to SIMK in vitro in protein interaction assays. Wound-induced MP2C expression correlates with the time window when SIMK is inactivated, corroborating the notion that MP2C is involved in resetting the SIMK signaling pathway.
authors.affiliation: Institute of Microbiology and Genetics, Vienna Biocenter, Dr. Bohrgasse 9, A-1030 Vienna, Austria. irute@gem.univie.ac.at
authors.forename: Irute
authors.initials: I
authors.lastname: Meskiene
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Baudouin
authors.forename: Alois
authors.initials: A
authors.lastname: Schweighofer
authors.forename: Aneta
authors.initials: A
authors.lastname: Liwosz
authors.forename: Claudia
authors.initials: C
authors.lastname: Jonak
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Rodriguez
authors.forename: Heinrich
authors.initials: H
authors.lastname: Jelinek
authors.forename: Heribert
authors.initials: H
authors.lastname: Hirt
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D002364:Caseins / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007163:Immunosorbent Techniques; D000455:Medicago sativa / Q000201:enzymology* / Q000235:genetics; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D010936:Plant Extracts; D018515:Plant Leaves / Q000201:enzymology; D010940:Plant Proteins; D000071636:Protein Phosphatase 2C; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D014638:Vanadates / Q000494:pharmacology
chemical_list: D002364:Caseins; D004791:Enzyme Inhibitors; D010936:Plant Extracts; D010940:Plant Proteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D011994:Recombinant Proteins; D019319:Okadaic Acid; D013912:Threonine; D014638:Vanadates; D003513:Cycloheximide; D004492:Edetic Acid; D020928:Mitogen-Activated Protein Kinases; C419564:salt stress-induced MAP kinase; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C