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Item 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 KrishnaLiving 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.Item Possible role of WRKY transcription factors in regulating immunity in Oryza sativa ssp. indica(Elsevier B.V., 2021) Sheikh, Arsheed H.; Hussain, Rana M. Fraz; Tabassum, Naheed; Badmi, Raghuram; Marillonnet, Sylvestre; Scheel, Dierk; Lee, Justin; Sinha, Alok KrishnaPlants have developed a robust transcription machinery to combat potential pathogenic organisms. One of the hallmarks of early immune responses is the activation of the WRKY transcription factors post infection. Specific WRKYs proteins from Arabidopsis are known substrates of MAPK pathway to mediate the flg22 elicited early immunity. In the current study, using the Golden Gate cloning strategy, we aim to clone the entire WRKY transcription factor family from Oryza sativa ssp. indica consisting of more than 100 members and study their MAPK interaction and subsequent role in PTI. Using a reporter LUC assay in protoplasts we investigated the early defense responses in a few interesting OsWRKY candidates. Interestingly, we observed stringent regulation of WRKY expression in cells and their transcriptional expression only under specific stress responses. The phenomenon of gene expression regulation by intron retention (IR) was prevalently observed in rice WRKY transcripts. We could show the role of WRKY8, 24, and 77 in early defense responses. It was observed that WRKY24 enhanced the expression of early defense response marker genes like NHL10 while WRKY8 and WRKY77 supressed their expression. This study highlights the complicated mechanism by which OsWRKYs expression is possibly regulated and the distinctive roles of some individual members in plant immunity. At the same time this study serves as a cautionary warning for plant researchers to be mindful of the intron retention mechanism while cloning OsWRKYs.Item 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 KrishnaMYC2, 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.
