Publications of NIPGR Scientists

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Author: search.filters.author.Sinha, Alok KrishnaSubject: search.filters.subject.Phosphorylation

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Now showing 1 - 6 of 6
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    Unveiling the molecular mechanism underlying PSKR-mediated amplification of the ABA signaling in Arabidopsis thaliana
    (Springer Nature Publishing AG, 2025) Yadav, Nikita; Nagar, Preeti ; Rawat, Abhilasha ; Rakhi, R. ; Singh, Dhanraj; Habibzai, Hedayaturahman ; Sinha, Alok Krishna; Mustafiz, Ananda 
    Abscisic acid (ABA) serves as a vital signaling molecule that help plants respond to various environmental stresses, ensuring their survival and adaptability. The ABA signaling pathway begins when ABA is recognized by receptors known as PYR/PYL/RCAR. Upon ABA binding, these receptors undergo structural changes, but the precise modifications occurring during post-translational stages and their impact on ABA signaling are not fully understood. In this study, we have identified and characterized the ABA receptor family as target of PSKRs in both Arabidopsis and rice. In addition, we pinpointed the critical active sites in AtPSKR1 (N865) and OsPSKR15 (N892) that are responsible for kinase activity of the respective receptors and also important for direct interaction with ABA receptors. In vitro kinase experiments demonstrated phosphorylation of ABA receptors at S99 in AtPYL4, and S79 in AtPYL9. In addition, our genetic analysis demonstrated that PSKR plays a positive role in regulating ABA-mediated physiological responses, and promotes ABA-dependent leaf senescence in Arabidopsis. Phenotypic studies and expression analysis of ABA-related genes in complementation lines (AtPSKR1:pyl9 and OsPSKR15:pyl9) suggested that the overexpression of PSKR can partially restore the insensitivity of pyl9 mutant plants to ABA. These findings underscore the critical role of PSKR in enhancing ABA signaling via phosphorylation of PYL4/PYL9 in Arabidopsis.
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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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    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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    Regulation of photosynthetic light reaction proteins via reversible phosphorylation
    (Elsevier B.V., 2022) Jonwal, Sarvesh; Verma, Neetu; Sinha, Alok Krishna
    The regulation of photosynthesis occurs at different levels including the control of nuclear and plastid genes transcription, RNA processing and translation, protein translocation, assemblies and their post translational modifications. Out of all these, post translational modification enables rapid response of plants towards changing environmental conditions. Among all post-translational modifications, reversible phosphorylation is known to play a crucial role in the regulation of light reaction of photosynthesis. Although, phosphorylation of PS II subunits has been extensively studied but not much attention is given to other photosynthetic complexes such as PS I, Cytochrome b6f complex and ATP synthase. Phosphorylation reaction is known to protect photosynthetic apparatus in challenging environment conditions such as high light, elevated temperature, high salinity and drought. Recent studies have explored the role of photosynthetic protein phosphorylation in conferring plant immunity against the rice blast disease. The evolution of phosphorylation of different subunits of photosynthetic proteins occurred along with the evolution of plant lineage for their better adaptation to the changing environment conditions. In this review, we summarize the progress made in the research field of phosphorylation of photosynthetic proteins and highlights the missing links that need immediate attention.
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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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    Cloning and characterization of a novel LpWRKY1 transcription factor in tomato
    (Elsevier B.V., 2008) Hofmann, Markus Georg; Sinha, Alok Krishna; Proels, Reinhard Korbinian; Roitsch, Thomas
    The initiation of defence responses in plants is accompanied by fundamental changes in gene expression: the expression of pathogenesis- related genes is co-ordinately regulated with metabolic changes such as down regulation of photosynthesis and induction of sink metabolism. To identify candidate regulators of this co-ordinated regulatory mechanism, the role of WRKY transcription factors in the initiation of defence response was analysed in tomato. A WRKY-type transcription factor (LpWRKY1) from tomato was cloned by a reverse Northern approach. The corresponding mRNA is rapidly and transiently induced after challenging the cells with an elicitor-preparation derived from the wilt inducing fungus Fusarium oxysporum lycopersici (E-FOL) and the fungal elicitor chitosan, whereas the endogenous signals systemin and salicylic acid are inactive. Inhibition of protein biosynthesis by cycloheximide results in sustained induction of mRNA for LpWRKY1. In contrast, the transient induction of the gene encoding LpWRKY1 in response to elicitation by E-FOL is inhibited by the protein-kinase inhibitor staurosporine and may be mimicked by the phosphatase inhibitors endothall and cantharidine indicating the involvement of protein phosphorylation in the regulation of WRKY-type transcription factors. Direct proof of this postranslational modification of LpWRKY1 was obtained by demonstrating in-gel kinase assays using recombinant LpWRKY1 as substrate. A 44 kDa and a 67 kDa protein kinase were shown to be transiently activated to phosphorylate LpWRKY1 protein in response to elicitation with E-FOL.