Rekha Agrawal

Oak Ridge National Laboratory

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Jitendra K. Thakur

National Institute of Plant Genome Research

Pallabi Thakur

National Institute of Plant Genome Research

A.D. Singh

Weill Cornell Medicine

Jin‐Gui Chen

Oak Ridge National Laboratory

Xiaohan Yang

Oak Ridge National Laboratory

Poonam Panchal

International Centre for Genetic Engineering and Biotechnology

Nidhi Dwivedi

Hindu Rao Hospital

Sourobh Maji

University of Delhi

Md Torikul Islam

Oak Ridge National Laboratory

Jiřı́ Fajkus

Central European Institute of Technology

Cooperative Institutions

Oak Ridge National Laboratory

National Institute of Plant Genome Research

University of Delhi

International Centre for Genetic Engineering and Biotechnology

University of Tennessee at Knoxville

Bioenergy Life Science (United States)

Baba Ghulam Shah Badshah University

Oak Ridge Associated Universities

Ministry of Agriculture and Rural Affairs

Indian Agricultural Research Institute

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The kinase module of the Mediator complex: an important signalling processor for the development and survival of plants

Journal of Experimental Botany (2020)

Rekha Agrawal Jiřı́ Fajkus Jitendra K. Thakur

Mediator, a multisubunit protein complex, is a signal processor that conveys regulatory information from transcription factors to RNA polymerase II and therefore plays an important role in the regulation of gene expression. This megadalton complex comprises four modules, namely, the head, middle, tail, and kinase modules. The first three modules form the core part of the complex, whereas association of the kinase module is facultative. The kinase module is able to alter the function of Mediator and has been established as a major transcriptional regulator of numerous developmental and biochemical processes. The kinase module consists of MED12, MED13, CycC, and kinase CDK8. Upon association with Mediator, the kinase module can alter its structure and function dramatically. In the past decade, research has established that the kinase module is very important for plant growth and development, and in the fight against biotic and abiotic challenges. However, there has been no comprehensive review discussing these findings in detail and depth. In this review, we survey the regulation of kinase module subunits and highlight their many functions in plants. Coordination between the subunits to process different signals for optimum plant growth and development is also discussed.

Mediator

10.1093/jxb/eraa439

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Citations (23)

Mediator Subunit, Med14, Regulates Pre- and Post-Fertilization Developmental Events in <i>Arabidopsis</i>

SSRN Electronic Journal (2021)

Sourobh Maji Nidhi Dwivedi Pallabi Thakur Anjitha Krishna P R Rekha Agrawal

In flowering plants, transitions from vegetative-to-reproductive and reproductive-to-seed stages are tightly regulated by coordinated activity of multiple transcription factors and cofactors. However, the mechanism of communication and coordination between these transcription regulators during ovule and seed development is not fully understood. This study reveals that the Mediator subunit MED14 integrates transcriptional signals from different transcription factors during pre-and post-fertilization developmental events in Arabidopsis. This is also the first study to demonstrate the importance of parental contribution of any Mediator subunit. We found that the promoter of AtMED14 is active in the auxin maxima regions of meristematic zones. We were unable to obtain any homozygous line of MED14 knock-out. The heterozygous mutants of med14 show defects in embryo sac, fertilization, and seed development. The genetic and cytological analyses revealed that the defective maternal sporophytic reproductive part of the med14+/- mutant is responsible for the fertilization defects. Some of the med14 embryos are arrested at globular stage whereas few others have uncontrolled cell division forming globular mass of cells. The auxin signaling essential for the ovule, embryo and seed development is compromised in med14 mutants. Further, MED14 is also important for seed coat development and its mucilage content as it interacts with different transcription regulators like ANT, WUS, LUG, MYB5, KNAT7 and LUH to regulate the expression of enzymes like MUM2 and MUM4 that are required for the synthesis of seed mucilage and its release, respectively. Overall, this study establishes MED14 as an important convergence point of transcriptional signals from various transcription factors required for development of gynoecium and seed in Arabidopsis.

Mediator

10.2139/ssrn.3782777

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Collaboration between DELLA and MED15 to regulate transcription in plants

Journal of Experimental Botany (2024)

Poonam Panchal Rashmi Ranjan Sutar Rekha Agrawal Jitendra K. Thakur

Gibberellins (GA) are diterpenoids that are categorized as one of main hormones that promote major developmental responses such as germination and stem elongation in plants. DELLA proteins act as the key repressors of GA responses. They interact with hundreds of different proteins. While the functioning of DELLA as transcriptional coactivators has also been reported earlier, the actual mechanism still remains elusive. One recent report describes interaction of DELLA with Mediator subunit MED15 as one of the mechanisms contributing to its transcription activation capability (Hernández-García et al. 2024). Interestingly, this mechanism of DELLA-MED15 module-mediated transcription regulation seems to be very ancient conserved from bryophyte Marchantia polymorpha to dicot Arabidopsis thaliana.

Transcription

General transcription factor

Mediator

10.1093/jxb/erae393

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MEDIATOR SUBUNIT17 integrates jasmonate and auxin signaling pathways to regulate thermomorphogenesis

PLANT PHYSIOLOGY (2022)

Rekha Agrawal Mohan Sharma Nidhi Dwivedi Sourobh Maji Pallabi Thakur

Abstract Plant adjustment to environmental changes involves complex crosstalk between extrinsic and intrinsic cues. In the past two decades, extensive research has elucidated the key roles of PHYTOCHROME-INTERACTING FACTOR4 (PIF4) and the phytohormone auxin in thermomorphogenesis. In this study, we identified a previously unexplored role of jasmonate (JA) signaling components, the Mediator complex, and their integration with auxin signaling during thermomorphogenesis in Arabidopsis (Arabidopsis thaliana). Warm temperature induces expression of JA signaling genes including MYC2, but, surprisingly, this transcriptional activation is not JA dependent. Warm temperature also promotes accumulation of the JA signaling receptor CORONATINE INSENSITIVE1 (COI1) and degradation of the JA signaling repressor JASMONATE-ZIM-DOMAIN PROTEIN9, which probably leads to de-repression of MYC2, enabling it to contribute to the expression of MEDIATOR SUBUNIT17 (MED17). In response to warm temperature, MED17 occupies the promoters of thermosensory genes including PIF4, YUCCA8 (YUC8), INDOLE-3-ACETIC ACID INDUCIBLE19 (IAA19), and IAA29. Moreover, MED17 facilitates enrichment of H3K4me3 on the promoters of PIF4, YUC8, IAA19, and IAA29 genes. Interestingly, both occupancy of MED17 and enrichment of H3K4me3 on these thermomorphogenesis-related promoters are dependent on PIF4 (or PIFs). Altered accumulation of COI1 under warm temperature in the med17 mutant suggests the possibility of a feedback mechanism. Overall, this study reveals the role of the Mediator complex as an integrator of JA and auxin signaling pathways during thermomorphogenesis.

Jasmonate

Crosstalk

Mediator

Methyl jasmonate

10.1093/plphys/kiac220

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A split ribozyme system for in vivo plant RNA imaging and genetic engineering

Plant Biotechnology Journal (2025)

Yang Liu Ruchika Rajput Md Torikul Islam Ilenne Del Valle Tao Yao

Summary RNA plays a central role in plants, governing various cellular and physiological processes. Monitoring its dynamic abundance provides a discerning understanding of molecular mechanisms underlying plant responses to internal (developmental) and external (environmental) stimuli, paving the way for advances in plant biotechnology to engineer crops with improved resilience, quality and productivity. In general, traditional methods for analysis of RNA abundance in plants require destructive, labour‐intensive and time‐consuming assays. To overcome these limitations, we developed a transformative innovation for in vivo RNA imaging in plants. Specifically, we established a synthetic split ribozyme system that converts various RNA signals to orthogonal protein outputs, enabling in vivo visualisation of various RNA signals in plants. We demonstrated the utility of this system in transient expression experiments (i.e., leaf infiltration in Nicotiana benthamiana ) to detect RNAs derived from transgenes and tobacco rattle virus, respectively. Also, we successfully engineered a split ribozyme‐based biosensor in Arabidopsis thaliana for in vivo visualisation of endogenous gene expression at the cellular level, demonstrating the feasibility of multi‐scale (e.g., cellular and tissue level) RNA imaging in plants. Furthermore, we developed a platform for easy incorporation of different protein outputs, allowing for flexible choice of reporters to optimise the detection of target RNAs.

Synthetic Biology

10.1111/pbi.14612

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Epigenetic and chromatin based plant stress adaptation

Elsevier eBooks (2025)

Rekha Agrawal Amrendra Kumar Chaudhary Amrita Singh Jitendra K. Thakur

10.1016/b978-0-443-13490-6.00016-3

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Mediator complex: an important regulator of root system architecture

Journal of Experimental Botany (2024)

Rekha Agrawal Pallabi Thakur A.D. Singh Poonam Panchal Jitendra K. Thakur

Mediator, a multiprotein complex, is an important component of the transcription machinery. In plants, the latest reports from our group and some other studies have established that Mediator functions as a signal processor that conveys transcriptional signals from transcription factors to RNA polymerase II. It has been found to be involved in different developmental and stress-adaptation conditions ranging from embryo, root, and shoot development to flowering and senescence and also in response to different biotic and abiotic stresses. In the last one decade, significant progress has been made in understanding the role of Mediator subunits in root development. They have been shown to transcriptionally regulate development of almost all the components of root system architecture - primary root, lateral root and root hair. Their role has also been appreciated in nutrient acquisition through root. In this review, we have discussed all the known functions of Mediator subunits during root development. We have also highlighted the role of Mediator as a nodal point for processing different hormone signaling that regulate root morphogenesis and growth.

Mediator

Lateral root

RNA polymerase II

Transcription

10.1093/jxb/erae277

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Searching for nature-based solutions: Molecular ecology of an endangered Himalayan medicinal herb shows roadmap for conservation and sustainable utilization

Journal for Nature Conservation (2024)

Lubna Tariq Zahid Ahmed Mangral Shahid Ul Islam Rekha Agrawal Anzar Ahmad Khuroo

Diosgenin

10.1016/j.jnc.2024.126624

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Citations (1)

Epigenetic memory in plants for stress response and adaptation

Elsevier eBooks (2025)

Rekha Agrawal A.D. Singh Jitendra K. Thakur

10.1016/b978-0-443-13490-6.00017-5

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MEDIATOR SUBUNIT17 is required for transcriptional optimization of root system architecture in Arabidopsis

PLANT PHYSIOLOGY (2023)

Rekha Agrawal A.D. Singh Jitender Giri Zoltán Magyar Jitendra K. Thakur

Abstract Sucrose and auxin are well-known determinants of root system architecture (RSA). However, the factors that connect the signaling pathways evoked by these two critical factors during root development are poorly understood. In this study, we report the role of MEDIATOR SUBUNIT17 (MED17) in RSA and its involvement in the transcriptional integration of sugar and auxin signaling pathways in Arabidopsis (Arabidopsis thaliana). Sucrose regulates root meristem activation through the TARGET OF RAPAMYCIN-E2 PROMOTER BINDING FACTOR A (TOR-E2FA) pathway, and auxin regulates lateral root (LR) development through AUXIN RESPONSE FACTOR-LATERAL ORGAN BOUNDARIES DOMAIN (ARF-LBDs). Both sucrose and auxin play a vital role during primary and LR development. However, there is no clarity on how sucrose is involved in the ARF-dependent regulation of auxin-responsive genes. This study establishes MED17 as a nodal point to connect sucrose and auxin signaling. Transcription of MED17 was induced by sucrose in an E2FA/B-dependent manner. Moreover, E2FA/B interacted with MED17, which can aid in the recruitment of the Mediator complex on the target promoters. Interestingly, E2FA/B and MED17 also occupied the promoter of ARF7, but not ARF19, leading to ARF7 expression, which then activates auxin signaling and thus initiates LR development. MED17 also activated cell division in the root meristem by occupying the promoters of cell–cycle genes, thus regulating their transcription. Thus, MED17 plays an important role in relaying the transcriptional signal from sucrose to auxin-responsive and cell–cycle genes to regulate primary and lateral root development, highlighting the role of the Mediator as the transcriptional processor for optimal root system architecture in Arabidopsis.

Lateral root

Mediator

10.1093/plphys/kiad129

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Citations (11)