Publications of NIPGR Scientists

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Author: search.filters.author.Bhagat, Prakash KumarSubject: search.filters.subject.MPK6

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    Arabidopsis MPK3 and MPK6 regulates D-Glucose signaling and interacts with G-Protein, RGS1
    (Elsevier B.V., 2022) Bhagat, Prakash Kumar; Sharma, Deepika; Verma, Deepanjali; Singh, Kirti; Sinha, Alok Krishna
    Sugar as a signaling molecule has attracted lots of attention. Even though several kinases have been shown to play a crucial role in the sugar signaling and response to exogenous D-glucose (Glc), the information on the involvement of MAP kinase cascade in sugar signaling has remain largely unexplored. In this report we demonstrate that MAP kinase signaling is essential for sensitivity to higher concentrations of D-Glc in Arabidopsis. We found that D-Glc activates MAP kinases, MPK3 and MPK6 in a concentration and time-dependent manner. The mutants of mpk3 and mpk6 display hyposensitivity to 6% D-Glc during seed germination, cotyledon greening and root growth. Interestingly, the altered sensitivity to increased D-Glc is severely enhanced by addition of 1% Sucrose in the media. Our study also deciphered the role of one of the Glc sensor proteins, RGS1 that interacts and gets phosphorylated at its C-terminal domain by MPK3 and MPK6. Overall our study provides a new insight on the involvement of MAP kinases in association with G-proteins that might regulate sugar signaling and sugar responsive growth and development in Arabidopsis.
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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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    MKK3-MPK6-MYC2 module positively regulates ABA biosynthesis and signalling in Arabidopsis
    (Springer Nature Publishing AG, 2020) Verma, Deepanjali; Bhagat, Prakash Kumar; Sinha, Alok Krishna
    Involvement of MAPK cascades is well studied in the regulation of ABA mediated responses such as stomatal opening, seed germination and stress tolerance. However most of the studies have focused on ABA signalling and involvement of MAPKs in ABA biosynthesis remains elusive. Hence, in the current study, we have identified the new role of MKK3- MPK6-MYC2 module in positive regulation of ABA biosynthesis as well as ABA responsive genes. Seed germination studies disclosed the ABA insensitive phenotype of myc2, mpk6 and mkk3 mutants. Reduced expression of ABA biosynthesis genes, ABA2 and NCED3 in myc2 and MAPK cascade mutants was confirmed by witnessing the direct binding of MYC2 to the promoter of ABA2 in EMSA assays. Additionally, ABA responsive genes also displayed altered expression patterns in these mutants. Further, transcript and biochemical studies validated the role of MPK6 upstream to MYC2 and downstream to MKK3 in response to ABA. Altogether, we have shown that MKK3-MPK6-MYC2 module induces the expression of several ABA related genes and regulate ABA mediated inhibition of seed germination.
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    A bHLH transcription factor, MYC2, imparts salt intolerance by regulating proline biosynthesis in Arabidopsis
    (John Wiley & Sons, 2020) Verma, Deepanjali; Jalmi, Siddhi Kashinath; Bhagat, Prakash Kumar; Verma, Neetu; Sinha, Alok Krishna
    MYC2, a bHLH TF, acts as regulatory hub within several signaling pathways by integration of various endogenous and exogenous signals which shape plant growth and development. However, its involvement in salt stress regulation is still elusive. This study has deciphered a novel role of MYC2 in imparting salt stress intolerance by regulating P5CS1 gene and hence proline synthesis. P5CS1 is a rate limiting enzyme in the biosynthesis of proline. Y‐1‐H and EMSA studies confirmed the binding of MYC2 with the 5’ UTR region of P5CS1. Transcript and biochemical studies have revealed MYC2 as a negative regulator of proline biosynthesis. Proline is necessary for imparting tolerance towards abiotic stress however, its overaccumulation is toxic for the plants. Hence studying the regulation of proline biosynthesis is requisite to understand the mechanism of stress tolerance. We have also studied that MYC2 is regulated by MAPK cascade MKK3‐MPK6 and vice versa. Altogether, this study demonstrates salt stress mediated activation of MYC2 by MAPK cascade, regulating proline biosynthesis and thus salt stress.