The Arabidopsis Mitogen-Activated Protein Kinase Phosphatase PP2C5 Affects Seed Germination, Stomatal Aperture, and Abscisic Acid-Inducible Gene Expression

• Published in: Plant physiology (Bethesda) Vol. 153; no. 3; pp. 1098 - 1111
• Main Authors: Brock, Anita K., Willmann, Roland, Kolb, Dagmar, Grefen, Laure, Lajunen, Heini M., Bethke, Gerit, Lee, Justin, Nürnberger, Thorsten, Gust, Andrea A.
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01-07-2010
• Subjects: Abscisic Acid - pharmacology; Arabidopsis - drug effects; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Biological and medical sciences; Cell Nucleus - drug effects; Cell Nucleus - enzymology; DEVELOPMENT AND HORMONE ACTION; Enzyme Activation - drug effects; Fundamental and applied biological sciences. Psychology; Gene expression; Gene expression regulation; Gene Expression Regulation, Enzymologic - drug effects; Gene Expression Regulation, Plant - drug effects; Gene Knockout Techniques; Germination - drug effects; Mitogen-Activated Protein Kinase Phosphatases - genetics; Mitogen-Activated Protein Kinase Phosphatases - metabolism; Mutation - genetics; Phosphatases; Plant cells; Plant physiology and development; Plant Stomata - anatomy & histology; Plant Stomata - drug effects; Plant Stomata - genetics; Plants; Protein Binding - drug effects; Protein Transport - drug effects; Proteins; Regulator genes; Seed germination; Seedlings; Seeds - drug effects; Seeds - enzymology; Seeds - genetics; Seeds - growth & development; Signal transduction; Stress, Physiological - drug effects; Stress, Physiological - genetics; Seeds; Enzyme; Transferases; Germination; Mitogen-activated protein kinase; Phosphoric monoester hydrolases; Esterases; Gene expression; Arabidopsis thaliana; Plant physiology; Cruciferae; Dicotyledones; Sesquiterpenes; Angiospermae; Stomatal movement; Abscisic acid; Hydrolases; Plant growth substance; Spermatophyta; Experimental plant
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.110.156109

Abscisic acid (ABA) is an important phytohormone regulating various cellular processes in plants, including stomatal opening and seed germination. Although protein phosphorylation via mitogen-activated protein kinases (MAPKs) has been suggested to be important in ABA signaling, the corresponding phosphatases are largely unknown. Here, we show that a member of the Protein Phosphatase 2C (PP2C) family in Arabidopsis (Arabidopsis thaliana), PP2C5, is acting as a MAPK phosphatase. The PP2C5 protein colocalizes and directly interacts with stress-induced MPK3, MPK4, and MPK6, predominantly in the nucleus. Importantly, altered PP2C5 levels affect MAPK activation. Whereas Arabidopsis plants depleted of PP2C5 show an enhanced ABA-induced activation of MPK3 and MPK6, ectopic expression of PP2C5 in tobacco (Nicotiana benthamiana) resulted in the opposite effect, with the two MAPKs salicylic acid-induced protein kinase and wound-induced protein kinase not being activated any longer after ABA treatment. Moreover, depletion of PP2C5, whose gene expression itself is affected by ABA treatment, resulted in altered ABA responses. Loss-of-function mutation in PP2C5 or AP2C1, a close PP2C5 homolog, resulted in an increased stomatal aperture under normal growth conditions and a partial ABA-insensitive phenotype in seed germination that was most prominent in the pp2c5 ap2c1 double mutant line. In addition, the response of ABA-inducible genes such as ABI1, ABI2, RD29A, and Erd10 was reduced in the mutant plants. Thus, we suggest that PP2C5 acts as a MAPK phosphatase that positively regulates seed germination, stomatal closure, and ABA-inducible gene expression.