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IN BRIEF

Phosphatase AP2C1 Is a Key Component of MAPK Signaling in Arabidopsis

neckardt{at}aspb.org

MAPK signaling is prevalent among eukaryotes and is implicated in the regulation of numerous processes, including the cell cycle and cell proliferation, differentiaton, and development, and environmental responses. MAPKs function as a component of a kinase signaling cascade that operates through sequential phosphorylation steps, wherein a MAPK kinase kinase phosphorylates a MAPK kinase, which in turn phosphorylates a MAPK. A phosphorylated MAPK is capable of phosphorylating other substrates, such as transcription factors. Several Arabidopsis MAPKs have been identified as components of stress response and plant defense signaling pathways receiving input from jasmonic acid, ethylene, salicylic acid, and other signals. MAPK cascades may provide for intricate control over cellular responses. For example, in the case of ethylene signaling in plants, MAPK signaling feeds forward to various downstream responses and feeds back to affect ethylene biosynthesis.

A critical component of MAPK signaling is provided by phosphatases that dephosphorylate and inactivate MAPKs, but this aspect of MAPK signaling is not well understood. Schweighofer et al. (pages 2213–2224) show that the Arabidopsis Ser/Thr phosphatase AP2C1 inactivates the stress-responsive MAPKs MPK4 and MPK6. This function of AP2C1 was found to play an important role in plant response to environmental stress related to jasmonate and ethylene signaling, including wounding, herbivore attack, and challenge with necrotrophic pathogens. The results suggest that under some circumstances, AP2C1 may control the amount of damage the plant incurs in response to biotic challenge through its regulation of MAPK signaling.

View larger version (102K): [in this window] [in a new window] [as a PowerPoint slide]   Compared with the wild type (top panel), overexpression of AP2C1 (bottom panel) led to inactivation of stress-responsive MAPKs and enhanced susceptibility to the necrotophic pathogen Botrytis cinerea.

www.plantcell.org/cgi/doi/10.1105/tpc.107.190710

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The PP2C-Type Phosphatase AP2C1, Which Negatively Regulates MPK4 and MPK6, Modulates Innate Immunity, Jasmonic Acid, and Ethylene Levels in Arabidopsis

Alois Schweighofer, Vaiva Kazanaviciute, Elisabeth Scheikl, Markus Teige, Robert Doczi, Heribert Hirt, Manfred Schwanninger, Merijn Kant, Robert Schuurink, Felix Mauch, Antony Buchala, Francesca Cardinale, and Irute Meskiene
Plant Cell 2007 19: 2213-2224. [Abstract] [Full Text]  

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