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Subject: search.filters.subject.Dephosphorylation

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    A dual-specificity phosphatase, MAP kinase phosphatase 1, positively regulates blue light-mediated seedling development in Arabidopsis
    (Springer Nature Publishing AG, 2021) Verma, Deepanjali; Bhagat, Prakash Kumar; Sinha, Alok Krishna
    Reversible phosphorylation of proteins is one of the major post-translational modifications in nearly all signaling pathways in plants. MAP kinase phosphatases are very crucial in the regulation of MAPKs as they dephosphorylate both threonine (Thr) and tyrosine (Tyr) residues within the T-X-Y motif of active MAPKs. Therefore, to gain insight of involvement of MAP kinase phosphatases in the regulation of light signaling, we searched for the potential phosphatase which may regulate the function of MPK6, a negative regulator of blue light (BL)-mediated photomorphogenic development. We report here the identification of a dual-specificity phosphatase, MAP kinase phosphatase 1 (MKP1) as a positive regulator of BL-mediated seedling development. Overexpression of MKP1 enhances the BL-induced inhibition of hypocotyl elongation and displays more opened cotyledons. We also show that MKP1OE accumulates more pigments and positively affects the expression of downstream light-related genes in response to BL. In vitro and in vivo evidences also demonstrate that MKP1 not only interacts with but also dephosphorylates MPK6 in BL. In addition, MKP1 regulates stability as well as activity of MPK6 upon BL. Taken together our study highlights the important role of phosphatases in the regulation of a signaling pathway and identifies the role of MKP1 in the negative regulation of MPK6 activity leading to a change in BL-induced photomorphogenic responses.
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    A protein phosphatase 2C, AP2C1 interacts with and negatively regulates the function of CIPK9 under potassium deficient conditions in Arabidopsis
    (Oxford University Press, 2018) Singh, Amarjeet; Yadav, Akhilesh K.; Kaur, Kanwaljeet; Sanyal, Sibaji K.; Jha, Saroj K.; Fernandes, Joel L.; Sharma, Pankhuri; Tokas, Indu; Pandey, Amita; Luan, Sheng; Pandey, Girdhar K.
    Potassium (K+) is a major macronutrient required for plant growth. In response to low- K+ condition, an adaptive mechanism entails activation of the Ca2+ signaling network consisting of calcineurin B-like proteins (CBLs) and their interacting kinases (CIPKs) in plants. The CBL-interacting protein kinase 9 (CIPK9) is previously implicated in low-K+ responses in Arabidopsis thaliana. Here, we report a protein phosphatase 2C (PP2C), AP2C1, as an interactor of CIPK9. Fluorescence resonance energy transfer (FRET), bimolecular fluorescence complementation (BiFC) and co-localization analyses revealed that CIPK9 and AP2C1 interact in the cytoplasm. AP2C1 dephosphorylates the auto-phosphorylated form of CIPK9 in vitro, presenting a regulatory mechanism for CIPK9 function. Furthermore, genetic and molecular analysis revealed that ap2c1 null mutants (ap2c1-1 and ap2c1-2) are tolerant to low-K+ conditions, retained higher K+ content and showed higher expression of K+ deficiency related genes contrary to cipk9 mutants (cipk9-1 and cipk9-2). In contrast, transgenic plants overexpressing AP2C1 were sensitive to low-K+ conditions. Thus, this study shows that AP2C1 and CIPK9 interact to regulate K+-deficiency responses in Arabidopsis. CIPK9 functions as positive regulator whereas, AP2C1 acts as a negative regulator of Arabidopsis root growth and seedling development under low-K+ conditions.