Publications of NIPGR Scientists

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Author: search.filters.author.Gautam, ShikhaSubject: search.filters.subject.PIMT

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    The rice heat shock transcription factor OsHSFC1b increases seed weight, size, and vigor, but its function is disrupted by isoaspartyl modification
    (John Wiley & Sons, 2025) Achary, Rakesh Kumar; Kamble, Nitin Uttam; Gautam, Shikha; Hazra, Abhijit; Varshney, Vishal; Mahawar, Shivangi; Laha, Saroj; Majee, Manoj
    Plant optimizes seed size, weight, vigor, and various other features during seed development, which are important not only for their successful propagation and establishment but also for effective agriculture. Despite several studies conducted, understanding how plants coordinate the regulatory mechanisms to achieve optimal seed size, weight, and vigor remains elusive. Here, our study reveals the role of rice heat shock transcription factor OsHSFC1b in modulating various seed attributes. We observe that OsHSFC1b expression increases during the later stage of seed development and is primarily localized in the embryo. We found that hsfc1b genome-edited lines exhibit compromised seed size, weight, and vigor, while overexpression lines exhibit increased seed size, weight, and vigor compared with the wild-type seeds. Our study further reveals that OsHSFC1b improves seed vigor by activating HSPs and RFO biosynthetic genes involved in protection mechanisms, while also mediating seed size and weight by modulating auxin biosynthesis, endosperm development, and seed filling. We found that upon ageing and stressful environments, OsHSFC1b undergoes isoaspartyl modification that negatively impacts its biological function in seeds. Our MS/MS analyses confirm that asparagine residues near the DNA-binding domain and nuclear localization sequence of OsHSFC1b undergo isoaspartyl modification that adversely affects OsHSFC1b's transactivation activity. However, PROTEIN L-ISOASPARTYL METHYLTRANSFERASE interacts and repairs this isoaspartate-mediated damage, and restores the function of OsHSFC1b. Taken together, our study uncovers how isoaspartyl modification affects the transactivation ability of OsHSFC1b, yet the intervention of PIMT not only repairs this damage but also elevates agronomically important seed traits.
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    PROTEIN L-ISOASPARTYL METHYLTRANSFERASE protects enolase dysfunction by repairing isoaspartyl-induced damage and is positively implicated in agronomically important seed traits
    (John Wiley & Sons, 2024) Kamble, Nitin Uttam; Ghosh, Shraboni; Petla, Bhanu Prakash; Achary, Rakesh Kumar; Gautam, Shikha; Rao, Venkateswara; Salvi, Prafull; Hazra, Abhijit; Varshney, Vishal; Majee, Manoj
    The protein-repairing enzyme (PRE) PROTEIN L-ISOASPARTYL METHYLTRANSFERASE (PIMT) influences seed vigor by repairing isoaspartyl-mediated protein damage in seeds. However, PIMTs function in other seed traits, and the mechanisms by which PIMT affects such seed traits are still poorly understood. Herein, through molecular, biochemical, and genetic studies using overexpression and RNAi lines in Oryza sativa and Arabidopsis thaliana, we demonstrate that PIMT not only affects seed vigor but also affects seed size and weight by modulating enolase (ENO) activity. We have identified ENO2, a glycolytic enzyme, as a PIMT interacting protein through Y2H cDNA library screening, and this interaction was further validated by BiFC and co-immunoprecipitation assay. We show that mutation or suppression of ENO2 expression results in reduced seed vigor, seed size, and weight. We also proved that ENO2 undergoes isoAsp modification that affects its activity in both in vivo and in vitro conditions. Further, using MS/MS analyses, amino acid residues that undergo isoAsp modification in ENO2 were identified. We also demonstrate that PIMT repairs such isoAsp modification in ENO2 protein, protecting its vital cellular functions during seed maturation and storage, and plays a vital role in regulating seed size, weight, and seed vigor. Taken together, our study identified ENO2 as a novel substrate of PIMT, and both ENO2 and PIMT in turn implicate in agronomically important seed traits.