Institutional Publications

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Author: search.filters.author.Tayyeba, SumairaStart date: 2020

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    Mitogen-activated protein kinase 3/6 regulates the stability of AtIAA3 and AtIAA7 during auxin signaling in Arabidopsis
    (Elsevier B.V., 2026) Noryang, Stanzin; Manna, Mrinalini; Verma, Neetu; Singh, Kirti; Tayyeba, Sumaira; Sinha, Alok Krishna
    Auxin mediated Aux/IAA degradation is required to release the ARFs from the control of IAAs, and ARFs in the free forms perform their role of transcription activation or suppression in response to developmental ques. Auxin is known to tag IAAs for proteasomal degradation, but how this tagging is regulated has not been widely explored. Here we report that, in Arabidopsis, exogenous application of auxin activates MPK3/6 which in turn phosphorylate IAA3 and IAA7 at Ser-58 and Ser-26, respectively. Further, incubation of IAA3 and IAA7 with the protein extracts from auxin treated mpk3 or mpk6 single mutants increase the rate of degradation of IAAs. Consequently, the phospho-null mutants, IAA3S58A and IAA7S26A were observed to be comparatively more stable. Thus, MAP kinase-mediated phosphorylation destabilised IAA3 and IAA7 leading to their degradation. Additionally, over-expression of the phospho-dead mutant of IAA3 (35S:IAA3S58A) and complementation of iaa3 mutant with this phospho-dead mutant resulted in reduced primary root length because of increased stability and accumulation of IAA3. Interestingly, we found that a member of ARF, ARF7 regulated the expression of MPKs by binding to their respective promoters.
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    Phosphorylation of AGO1a by MAP kinases is required for miRNA mediated resistance against Xanthomonas oryzae pv. oryzae infection in rice
    (Elsevier B.V., 2024) Singh, Kirti; Sharma, Deepika; Bhagat, Prakash Kumar; Tayyeba, Sumaira; Noryang, Stanzin; Sinha, Alok Krishna
    Bacterial leaf blight is a devastating disease caused by Xanthomonas oryzae pv. oryzae (Xoo) which causes severe crop loss in rice. The molecular mechanism that initiates defense against such pathogens remains unexplored. Reports have suggested crucial role of several miRNAs in regulating immune responses in plants. Argonaute (AGO) proteins have been implicated in imparting immunity against pathogens by using small RNAs as guide molecules. Here, we show that phosphorylation of rice AGO1a by MAP kinases is required for miRNA expression regulation during Xoo infection. AGO1a is induced in response to pathogen infection and is under the control of SA signaling pathway. The pathogen responsive MAP kinases MPK3, MPK4 and MPK6, interact with AGO1a in planta and can phosphorylate the protein in vitro. Overexpression of AGO1a extends disease resistance against Xoo in rice and leads to a higher accumulation of miRNAs. Conversely, overexpression of a non phosphorylatable mutant protein aggravates disease susceptibility and remarkably suppresses the miRNA expression levels. At a molecular level, phosphorylation of AGO1a by MAP kinase is required for increased accumulation of miRNAs during pathogen challenge. Taken together, the data suggests that OsAGO1a is a direct phosphorylation target of MAP kinases and this phosphorylation is crucial for its role in imparting disease resistance.
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    Finding a breather for Oryza sativa: Understanding hormone signalling pathways involved in rice plants to submergence stress
    (John Wiley & Sons, 2022) Mittal, Lavanya; Tayyeba, Sumaira; Sinha, Alok Krishna
    During the course of evolution, different ecotypes of rice (Oryza sativa L.) have evolved distinct strategies to cope with submergence stress. Such contrasting responses are mediated by plant hormones that are principle regulators of growth, development and responses to various biotic and abiotic stresses. These hormones act cooperatively and show extensive crosstalk which is mediated by key regulatory genes that serve as nodes of molecular communication. The presence or absence of such genes leads to significant changes in hormone signalling pathways and hence, governs the type of response that the plant will exhibit. As flooding is one of the leading causes of crop loss across all the major rice-producing countries, it is crucial to deeply understand the molecular nexus governing the response to submergence to produce flood resilient varieties. This review focuses on the hormonal signalling pathways that mediate two contrasting responses of the rice plant to submergence stress namely, rapid internode elongation to escape flood waters and quiescence response that enables the plant to survive under complete submergence. The significance of several key genes such as Sub1A-1, SLR1, SD1 and SK1/SK2, in defining the ultimate response to submergence has also been discussed.
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    MAP kinase as regulators for stress responses in plants: An overview
    (John Wiley & Sons, 2021) Sharma, Deepika; Verma, Neetu; Pandey, Chandana; Verma, Deepanjali; Bhagat, Prakash Kumar; Noryang, Stanzin; Singh, Kirti; Tayyeba, Sumaira; Banerjee, Gopal; Sinha, Alok Krishna
    Living cells adapt to various kind of stresses by perceiving changes in the extracellular environment and communicating these changes from outside of the cell to the inside and ultimately to the nucleus where expression of a specific set of genes occurs in order to provide appropriate response to the stress. Plant cells have evolved several signaling cascades to accomplish this signal transduction. One of the major mechanisms is the cascade of protein phosphorylation by specific Mitogen Activated Protein Kinase (MAPK) cascade. This cascade comprises of three kinase modules, a MAPK kinase kinase (MAPKKK/MAKKK/MEKK/MAP3K), a MAPK kinase (MAPKK/MKK/MEK/MAP2K) and a MAPK, which are sequentially activated by an event of protein phosphorylation. In plants, MAPKs are large signaling families of proteins, which have been shown to be involved in cross-talk with various abiotic and biotic stress responses forming complex networks in cells. Abiotic stresses such as heat, cold, changing light intensities, heavy metals and salinity, and biotic stress such as pathogen attack are key factors, which affect growth and development of plants. In response to these stresses, MAPK signaling cascade regulate growth of plants by transcriptional and post-transcriptional regulation such as protein–protein interactions. In this chapter, we discuss the latest findings and insights in relation to the role of all the modules, MAPKKK, MAPKK, and MAPKs of different MAPK signaling cascades in various abiotic and biotic stresses in plants.