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Freytes SN, Gobbini ML, Cerdán PD. The Plant Mediator Complex in the Initiation of Transcription by RNA Polymerase II. ANNUAL REVIEW OF PLANT BIOLOGY 2024; 75:211-237. [PMID: 38277699 DOI: 10.1146/annurev-arplant-070623-114005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2024]
Abstract
Thirty years have passed since the discovery of the Mediator complex in yeast. We are witnessing breakthroughs and advances that have led to high-resolution structural models of yeast and mammalian Mediators in the preinitiation complex, showing how it is assembled and how it positions the RNA polymerase II and its C-terminal domain (CTD) to facilitate the CTD phosphorylation that initiates transcription. This information may be also used to guide future plant research on the mechanisms of Mediator transcriptional control. Here, we review what we know about the subunit composition and structure of plant Mediators, the roles of the individual subunits and the genetic analyses that pioneered Mediator research, and how transcription factors recruit Mediators to regulatory regions adjoining promoters. What emerges from the research is a Mediator that regulates transcription activity and recruits hormonal signaling modules and histone-modifying activities to set up an off or on transcriptional state that recruits general transcription factors for preinitiation complex assembly.
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Affiliation(s)
| | | | - Pablo D Cerdán
- Fundación Instituto Leloir, IIBBA-CONICET, Buenos Aires, Argentina; , ,
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina
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Barbut FR, Cavel E, Donev EN, Gaboreanu I, Urbancsok J, Pandey G, Demailly H, Jiao D, Yassin Z, Derba-Maceluch M, Master ER, Scheepers G, Gutierrez L, Mellerowicz EJ. Integrity of xylan backbone affects plant responses to drought. FRONTIERS IN PLANT SCIENCE 2024; 15:1422701. [PMID: 38984158 PMCID: PMC11231379 DOI: 10.3389/fpls.2024.1422701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Accepted: 06/07/2024] [Indexed: 07/11/2024]
Abstract
Drought is a major factor affecting crops, thus efforts are needed to increase plant resilience to this abiotic stress. The overlapping signaling pathways between drought and cell wall integrity maintenance responses create a possibility of increasing drought resistance by modifying cell walls. Here, using herbaceous and woody plant model species, Arabidopsis and hybrid aspen, respectively, we investigated how the integrity of xylan in secondary walls affects the responses of plants to drought stress. Plants, in which secondary wall xylan integrity was reduced by expressing fungal GH10 and GH11 xylanases or by affecting genes involved in xylan backbone biosynthesis, were subjected to controlled drought while their physiological responses were continuously monitored by RGB, fluorescence, and/or hyperspectral cameras. For Arabidopsis, this was supplemented with survival test after complete water withdrawal and analyses of stomatal function and stem conductivity. All Arabidopsis xylan-impaired lines showed better survival upon complete watering withdrawal, increased stomatal density and delayed growth inhibition by moderate drought, indicating increased resilience to moderate drought associated with modified xylan integrity. Subtle differences were recorded between xylan biosynthesis mutants (irx9, irx10 and irx14) and xylanase-expressing lines. irx14 was the most drought resistant genotype, and the only genotype with increased lignin content and unaltered xylem conductivity despite its irx phenotype. Rosette growth was more affected by drought in GH11- than in GH10-expressing plants. In aspen, mild downregulation of GT43B and C genes did not affect drought responses and the transgenic plants grew better than the wild-type in drought and well-watered conditions. Both GH10 and GH11 xylanases strongly inhibited stem elongation and root growth in well-watered conditions but growth was less inhibited by drought in GH11-expressing plants than in wild-type. Overall, plants with xylan integrity impairment in secondary walls were less affected than wild-type by moderately reduced water availability but their responses also varied among genotypes and species. Thus, modifying the secondary cell wall integrity can be considered as a potential strategy for developing crops better suited to withstand water scarcity, but more research is needed to address the underlying molecular causes of this variability.
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Affiliation(s)
- Félix R Barbut
- Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, Umeå, Sweden
| | - Emilie Cavel
- Centre de Ressources Régionales en Biologie Moléculaire (CRRBM), University of Picardie Jules Verne, Amiens, France
| | - Evgeniy N Donev
- Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, Umeå, Sweden
| | - Ioana Gaboreanu
- Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, Umeå, Sweden
| | - János Urbancsok
- Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, Umeå, Sweden
| | - Garima Pandey
- Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, Umeå, Sweden
| | - Hervé Demailly
- Centre de Ressources Régionales en Biologie Moléculaire (CRRBM), University of Picardie Jules Verne, Amiens, France
| | - Dianyi Jiao
- Centre de Ressources Régionales en Biologie Moléculaire (CRRBM), University of Picardie Jules Verne, Amiens, France
| | - Zakiya Yassin
- RISE Research Institutes of Sweden, Built Environment Division, Stockholm, Sweden
| | - Marta Derba-Maceluch
- Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, Umeå, Sweden
| | - Emma R Master
- Department of Chemical Engineering and Applied Chemistry Department, University of Toronto, Toronto, ON, Canada
| | - Gerhard Scheepers
- RISE Research Institutes of Sweden, Built Environment Division, Stockholm, Sweden
| | - Laurent Gutierrez
- Centre de Ressources Régionales en Biologie Moléculaire (CRRBM), University of Picardie Jules Verne, Amiens, France
| | - Ewa J Mellerowicz
- Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, Umeå, Sweden
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Mu L, Wang X, Ma Y, Zhao A, Han S, Li R, Lei K, Ji L, Li P. Apple Glycosyltransferase MdUGT73AR4 Glycosylates ABA to Regulate Stomatal Movement Involved in Drought Stress. Int J Mol Sci 2024; 25:5672. [PMID: 38891859 PMCID: PMC11171509 DOI: 10.3390/ijms25115672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 05/17/2024] [Accepted: 05/21/2024] [Indexed: 06/21/2024] Open
Abstract
Abscisic acid (ABA) is a drought-stress-responsive hormone that plays an important role in the stomatal activity of plant leaves. Currently, ABA glycosides have been identified in apples, but their glycosyltransferases for glycosylation modification of ABA are still unidentified. In this study, the mRNA expression of glycosyltransferase gene MdUGT73AR4 was significantly up-regulated in mature apple leaves which were treated in drought stress by Real-Time PCR. It was hypothesised that MdUGT73AR4 might play an important role in drought stress. In order to further characterise the glycosylation modification substrate of glycosyltransferase MdUGT73AR4, we demonstrated through in vitro and in vivo functional validation that MdUGT73AR4 can glycosylate ABA. Moreover, the overexpression lines of MdUGT73AR4 significantly enhance its drought stress resistance function. We also found that the adversity stress transcription factor AREB1B might be an upstream transcription factor of MdUGT73AR4 by bioinformatics, EMSA, and ChIP experiments. In conclusion, this study found that the adversity stress transcription factor AREB1B was significantly up-regulated at the onset of drought stress, which in turn positively regulated the downstream glycosyltransferase MdUGT73AR4, causing it to modify ABA by mass glycosylation and promoting the ABA synthesis pathway, resulting in the accumulation of ABA content, and displaying a stress-resistant phenotype.
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Affiliation(s)
| | | | | | | | | | | | | | - Lusha Ji
- State Key Laboratory for Macromolecule Drugs and Large-Scale Manufacturing, School of Pharmaceutical Sciences, Liaocheng University, Liaocheng 252059, China; (L.M.); (X.W.); (Y.M.); (A.Z.); (S.H.); (R.L.); (K.L.)
| | - Pan Li
- State Key Laboratory for Macromolecule Drugs and Large-Scale Manufacturing, School of Pharmaceutical Sciences, Liaocheng University, Liaocheng 252059, China; (L.M.); (X.W.); (Y.M.); (A.Z.); (S.H.); (R.L.); (K.L.)
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Liang L, Wang D, Xu D, Xiao J, Tang W, Song X, Yu G, Liang Z, Xie M, Xu Z, Sun B, Tang Y, Huang Z, Lai Y, Li H. Comparative phylogenetic analysis of the mediator complex subunit in asparagus bean (Vigna unguiculata ssp. sesquipedialis) and its expression profile under cold stress. BMC Genomics 2024; 25:149. [PMID: 38321384 PMCID: PMC10848533 DOI: 10.1186/s12864-024-10060-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 01/29/2024] [Indexed: 02/08/2024] Open
Abstract
BACKGROUND The mediator complex subunits (MED) constitutes a multiprotein complex, with each subunit intricately involved in crucial aspects of plant growth, development, and responses to stress. Nevertheless, scant reports pertain to the VunMED gene within the context of asparagus bean (Vigna unguiculata ssp. sesquipedialis). Establishing the identification and exploring the responsiveness of VunMED to cold stress forms a robust foundation for the cultivation of cold-tolerant asparagus bean cultivars. RESULTS Within this study, a comprehensive genome-wide identification of VunMED genes was executed in the asparagus bean cultivar 'Ningjiang3', resulting in the discovery of 36 distinct VunMED genes. A phylogenetic analysis encompassing 232 MED genes from diverse species, including Arabidopsis, tomatoes, soybeans, mung beans, cowpeas, and asparagus beans, underscored the highly conserved nature of MED gene sequences. Throughout evolutionary processes, each VunMED gene underwent purification and neutral selection, with the exception of VunMED19a. Notably, VunMED9/10b/12/13/17/23 exhibited structural variations discernible across four cowpea species. Divergent patterns of temporal and spatial expression were evident among VunMED genes, with a prominent role attributed to most genes during early fruit development. Additionally, an analysis of promoter cis-acting elements was performed, followed by qRT-PCR assessments on roots, stems, and leaves to gauge relative expression after exposure to cold stress and subsequent recovery. Both treatments induced transcriptional alterations in VunMED genes, with particularly pronounced effects observed in root-based genes following cold stress. Elucidating the interrelationships between subunits involved a preliminary understanding facilitated by correlation and principal component analyses. CONCLUSIONS This study elucidates the pivotal contribution of VunMED genes to the growth, development, and response to cold stress in asparagus beans. Furthermore, it offers a valuable point of reference regarding the individual roles of MED subunits.
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Affiliation(s)
- Le Liang
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Dong Wang
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Dongmei Xu
- Mianyang Academy of Agricultural Sciences, Mianyang, 621000, China
| | - Jiachang Xiao
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Wen Tang
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Xueping Song
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Guofeng Yu
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Zongxu Liang
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Minghui Xie
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Zeping Xu
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Bo Sun
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Yi Tang
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Zhi Huang
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Yunsong Lai
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Huanxiu Li
- College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China.
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Panter PE, Seifert J, Dale M, Pridgeon AJ, Hulme R, Ramsay N, Contera S, Knight H. Cell wall fucosylation in Arabidopsis influences control of leaf water loss and alters stomatal development and mechanical properties. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:2680-2691. [PMID: 36715637 PMCID: PMC10112686 DOI: 10.1093/jxb/erad039] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 01/27/2023] [Indexed: 06/06/2023]
Abstract
The Arabidopsis sensitive-to-freezing8 (sfr8) mutant exhibits reduced cell wall (CW) fucose levels and compromised freezing tolerance. To examine whether CW fucosylation also affects the response to desiccation, we tested the effect of leaf excision in sfr8 and the allelic mutant mur1-1. Leaf water loss was strikingly higher than in the wild type in these, but not other, fucosylation mutants. We hypothesized that reduced fucosylation in guard cell (GC) walls might limit stomatal closure through altering mechanical properties. Multifrequency atomic force microscopy (AFM) measurements revealed a reduced elastic modulus (E'), representing reduced stiffness, in sfr8 GC walls. Interestingly, however, we discovered a compensatory mechanism whereby a concomitant reduction in the storage modulus (E'') maintained a wild-type viscoelastic time response (tau) in sfr8. Stomata in intact leaf discs of sfr8 responded normally to a closure stimulus, abscisic acid, suggesting that the time response may relate more to closure properties than stiffness does. sfr8 stomatal pore complexes were larger than those of the wild type, and GCs lacked a fully developed cuticular ledge, both potential contributors to the greater leaf water loss in sfr8. We present data that indicate that fucosylation-dependent dimerization of the CW pectic domain rhamnogalacturonan-II may be essential for normal cuticular ledge development and leaf water retention.
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Affiliation(s)
- Paige E Panter
- Department of Biosciences, Durham University, South Road, Durham, UK
| | - Jacob Seifert
- Department of Physics, University of Oxford, Parks Road, Oxford, UK
| | - Maeve Dale
- Department of Biosciences, Durham University, South Road, Durham, UK
- School of Biological Sciences, University of Bristol, Bristol, UK
| | | | - Rachel Hulme
- Department of Biosciences, Durham University, South Road, Durham, UK
| | - Nathan Ramsay
- Department of Biosciences, Durham University, South Road, Durham, UK
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Bajracharya A, Xi J, Grace KF, Bayer EE, Grant CA, Clutton CH, Baerson SR, Agarwal AK, Qiu Y. PHYTOCHROME-INTERACTING FACTOR 4/HEMERA-mediated thermosensory growth requires the Mediator subunit MED14. PLANT PHYSIOLOGY 2022; 190:2706-2721. [PMID: 36063057 PMCID: PMC9706435 DOI: 10.1093/plphys/kiac412] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 08/12/2022] [Indexed: 05/19/2023]
Abstract
While moderately elevated ambient temperatures do not trigger stress responses in plants, they do substantially stimulate the growth of specific organs through a process known as thermomorphogenesis. The basic helix-loop-helix transcription factor PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) plays a central role in regulating thermomorphogenetic hypocotyl elongation in various plant species, including Arabidopsis (Arabidopsis thaliana). Although it is well known that PIF4 and its co-activator HEMERA (HMR) promote plant thermosensory growth by activating genes involved in the biosynthesis and signaling of the phytohormone auxin, the detailed molecular mechanism of such transcriptional activation is not clear. In this report, we investigated the role of the Mediator complex in the PIF4/HMR-mediated thermoresponsive gene expression. Through the characterization of various mutants of the Mediator complex, a tail subunit named MED14 was identified as an essential factor for thermomorphogenetic hypocotyl growth. MED14 was required for the thermal induction of PIF4 target genes but had a marginal effect on the levels of PIF4 and HMR. Further transcriptomic analyses confirmed that the expression of numerous PIF4/HMR-dependent, auxin-related genes required MED14 at warm temperatures. Moreover, PIF4 and HMR physically interacted with MED14 and both were indispensable for the association of MED14 with the promoters of these thermoresponsive genes. While PIF4 did not regulate MED14 levels, HMR was required for the transcript abundance of MED14. Taken together, these results unveil an important thermomorphogenetic mechanism, in which PIF4 and HMR recruit the Mediator complex to activate auxin-related growth-promoting genes when plants sense moderate increases in ambient temperature.
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Affiliation(s)
| | - Jing Xi
- Natural Products Utilization Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Oxford, Mississippi, USA
| | - Karlie F Grace
- Department of Biology, University of Mississippi, Oxford, Mississippi 38677, USA
| | - Eden E Bayer
- Department of Biology, University of Mississippi, Oxford, Mississippi 38677, USA
| | - Chloe A Grant
- Department of Biology, University of Mississippi, Oxford, Mississippi 38677, USA
| | - Caroline H Clutton
- Department of Biology, University of Mississippi, Oxford, Mississippi 38677, USA
| | - Scott R Baerson
- Natural Products Utilization Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Oxford, Mississippi, USA
| | - Ameeta K Agarwal
- National Center for Natural Products Research, School of Pharmacy, University of Mississippi, Oxford, Mississippi, USA
- Division of Pharmacology, Department of BioMolecular Sciences, School of Pharmacy, University of Mississippi, Oxford, Mississippi, USA
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Chen J, Yang S, Fan B, Zhu C, Chen Z. The Mediator Complex: A Central Coordinator of Plant Adaptive Responses to Environmental Stresses. Int J Mol Sci 2022; 23:ijms23116170. [PMID: 35682844 PMCID: PMC9181133 DOI: 10.3390/ijms23116170] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 05/22/2022] [Accepted: 05/28/2022] [Indexed: 01/25/2023] Open
Abstract
As sessile organisms, plants are constantly exposed to a variety of environmental stresses and have evolved adaptive mechanisms, including transcriptional reprogramming, in order to survive or acclimate under adverse conditions. Over the past several decades, a large number of gene-specific transcription factors have been identified in the transcriptional regulation of plant adaptive responses. The Mediator complex plays a key role in transducing signals from gene-specific transcription factors to the transcription machinery to activate or repress target gene expression. Since its first purification about 15 years ago, plant Mediator complex has been extensively analyzed for its composition and biological functions. Mutants of many plant Mediator subunits are not lethal but are compromised in growth, development and response to biotic and abiotic stress, underscoring a particularly important role in plant adaptive responses. Plant Mediator subunits also interact with partners other than transcription factors and components of the transcription machinery, indicating the complexity of the regulation of gene expression by plant Mediator complex. Here, we present a comprehensive discussion of recent analyses of the structure and function of plant Mediator complex, with a particular focus on its roles in plant adaptive responses to a wide spectrum of environmental stresses and associated biological processes.
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Affiliation(s)
- Jialuo Chen
- College of Life Sciences, China Jiliang University, Hangzhou 310018, China; (J.C.); (S.Y.)
| | - Su Yang
- College of Life Sciences, China Jiliang University, Hangzhou 310018, China; (J.C.); (S.Y.)
| | - Baofang Fan
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA;
| | - Cheng Zhu
- College of Life Sciences, China Jiliang University, Hangzhou 310018, China; (J.C.); (S.Y.)
- Correspondence: (C.Z.); (Z.C.); Tel.: +86-571-8683-6090 (C.Z.); +1-765-494-4657 (Z.C.)
| | - Zhixiang Chen
- College of Life Sciences, China Jiliang University, Hangzhou 310018, China; (J.C.); (S.Y.)
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA;
- Correspondence: (C.Z.); (Z.C.); Tel.: +86-571-8683-6090 (C.Z.); +1-765-494-4657 (Z.C.)
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