Publications of NIPGR Scientists

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    Regulation of photosynthesis by mitogen-activated protein kinase in rice: antagonistic adjustment by OsMPK3 and OsMPK6
    (Springer Nature Publishing AG, 2023) Jonwal, Sarvesh; Rengasamy, Balakrishnan; Sinha, Alok Krishna
    Photosynthesis is the basis of almost all life on earth and is the main component of crop yield that contributes to the carbohydrate partitioning to the grains. Maintaining the photosynthetic efficiency of plants in challenging environmental conditions by regulating the associated factors is a potential research arena which will help in the improvement of crop yield. Phosphorylation is known to play a pivotal role in the regulation of photosynthesis. Mitogen Activated Protein Kinases (MAPKs) cascade although known to regulate a diverse range of processes does not have any exact reported function in the regulation of photosynthesis. To elucidate the regulatory role of MAPKs in photosynthesis we investigated the changes in net photosynthesis rate and related parameters in DEX inducible over-expressing (OE) lines of two members of MAPK gene family namely, OsMPK3 and OsMPK6 in rice. Interestingly, significant changes were found in net photosynthesis rate and related physiological parameters in OsMPK3 and OsMPK6-OE lines compared to its wild-type relatives. OsMPK3 and OsMPK6 have regulatory effects on nuclear-encoded photosynthetic genes. Untargeted metabolite profiling reveals a higher accumulation of sugars and their derivatives in MPK6 overexpressing plants and a lower accumulation of sugars and organic acids in MPK3 overexpressing plants. The accumulation of amino acids was found in abundance in both MPK3 and MPK6 overexpressing plants. Understanding the effects of MPK3 and MPK6 on the CO2 assimilation of rice plants under normal growth conditions, will help in devising strategies that can be extended for crop improvement.
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    Rice Mitogen-Activated Protein Kinase regulates serotonin accumulation and interacts with cell cycle regulators under prolonged UV-B exposure
    (Elsevier B.V., 2023) Banerjee, Gopal; Singh, Dhanraj; Pandey, Chandana; Jonwal, Sarvesh; Basu, Udita; Parida, Swarup K.; Pandey, Ashutosh; Sinha, Alok Krishna
    Stress conditions such as UV-B exposure activates MAPKs in Arabidopsis and rice. UV-B radiation is hazardous to plant as it causes photosystem disruption, DNA damage and ROS generation. Here we report its effect on biological pathways by studying the global changes in transcript profile in rice seedling exposed to UV-B radiation for 1 h and 16 h. Short UV-B exposure (1 h) led to moderate changes, while a drastic change in transcript landscape was observed after long term UV-B exposure (16 h) in rice seedlings. Prolonged UV-B exposure negatively impacts the expression of cell cycle regulating genes and several other metabolic pathways in developing seedlings. MAP kinase signaling cascade gets activated upon UV-B exposure similar to reports in Arabidopsis indicating conservation of its function in both dicot and monocot. Expression analysis in inducible overexpression transgenic lines of MPK3 and MPK6 shows higher transcript abundance of phytoalexin biosynthesis gene like Oryzalexin D synthase and Momilactone A synthase, along with serotonin biosynthesis genes. An accumulation of serotonin was observed upon UV-B exposure and its abundance positively correlates with the MPK3 and MPK6 transcript level in the respective over-expression lines. Interestingly, multiple cell cycle inhibitor proteins including WEE1 and SMR1 interact with MPK3 and MPK6 thus, implying a major role of this pathway in cell cycle regulation under stress condition. Overall overexpression of MPK3 and MPK6 found to be detrimental for rice as overexpression lines shows higher cell death and compromised tolerance to UV-B.
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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.