1
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Simon L, Probst AV. Maintenance and dynamic reprogramming of chromatin organization during development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2024; 118:657-670. [PMID: 36700345 DOI: 10.1111/tpj.16119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Revised: 01/20/2023] [Accepted: 01/23/2023] [Indexed: 06/17/2023]
Abstract
Controlled transcription of genes is critical for cell differentiation and development. Gene expression regulation therefore involves a multilayered control from nucleosome composition in histone variants and their post-translational modifications to higher-order folding of chromatin fibers and chromatin interactions in nuclear space. Recent technological advances have allowed gaining insight into these mechanisms, the interplay between local and higher-order chromatin organization, and the dynamic changes that occur during stress response and developmental transitions. In this review, we will discuss chromatin organization from the nucleosome to its three-dimensional structure in the nucleus, and consider how these different layers of organization are maintained during the cell cycle or rapidly reprogrammed during development.
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Affiliation(s)
- Lauriane Simon
- iGReD, CNRS, Inserm, Université Clermont Auvergne, 63000, Clermont-Ferrand, France
| | - Aline V Probst
- iGReD, CNRS, Inserm, Université Clermont Auvergne, 63000, Clermont-Ferrand, France
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2
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Candela-Ferre J, Diego-Martin B, Pérez-Alemany J, Gallego-Bartolomé J. Mind the gap: Epigenetic regulation of chromatin accessibility in plants. PLANT PHYSIOLOGY 2024; 194:1998-2016. [PMID: 38236303 PMCID: PMC10980423 DOI: 10.1093/plphys/kiae024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 11/07/2023] [Accepted: 11/23/2023] [Indexed: 01/19/2024]
Abstract
Chromatin plays a crucial role in genome compaction and is fundamental for regulating multiple nuclear processes. Nucleosomes, the basic building blocks of chromatin, are central in regulating these processes, determining chromatin accessibility by limiting access to DNA for various proteins and acting as important signaling hubs. The association of histones with DNA in nucleosomes and the folding of chromatin into higher-order structures are strongly influenced by a variety of epigenetic marks, including DNA methylation, histone variants, and histone post-translational modifications. Additionally, a wide array of chaperones and ATP-dependent remodelers regulate various aspects of nucleosome biology, including assembly, deposition, and positioning. This review provides an overview of recent advances in our mechanistic understanding of how nucleosomes and chromatin organization are regulated by epigenetic marks and remodelers in plants. Furthermore, we present current technologies for profiling chromatin accessibility and organization.
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Affiliation(s)
- Joan Candela-Ferre
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC-Universitat Politècnica de València, Valencia, 46022Spain
| | - Borja Diego-Martin
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC-Universitat Politècnica de València, Valencia, 46022Spain
| | - Jaime Pérez-Alemany
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC-Universitat Politècnica de València, Valencia, 46022Spain
| | - Javier Gallego-Bartolomé
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC-Universitat Politècnica de València, Valencia, 46022Spain
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3
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Long X, Yang W, Lv Y, Zhong X, Chen L, Li Q, Lv Z, Li Y, Cai Y, Yang H. The Histone Variant H3.3 Is Required for Plant Growth and Fertility in Arabidopsis. Int J Mol Sci 2024; 25:2549. [PMID: 38473796 DOI: 10.3390/ijms25052549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 02/19/2024] [Accepted: 02/20/2024] [Indexed: 03/14/2024] Open
Abstract
Histones are the core components of the eukaryote chromosome, and have been implicated in transcriptional gene regulation. There are three major isoforms of histone H3 in Arabidopsis. Studies have shown that the H3.3 variant is pivotal in modulating nucleosome structure and gene transcription. However, the function of H3.3 during development remains to be further investigated in plants. In this study, we disrupted all three H3.3 genes in Arabidopsis. Two triple mutants, h3.3cr-4 and h3.3cr-5, were created by the CRISPR/Cas9 system. The mutant plants displayed smaller rosettes and decreased fertility. The stunted growth of h3.3cr-4 may result from reduced expression of cell cycle regulators. The shorter stamen filaments, but not the fertile ability of the gametophytes, resulted in reduced fertility of h3.3cr-4. The transcriptome analysis suggested that the reduced filament elongation of h3.3cr-4 was probably caused by the ectopic expression of several JASMONATE-ZIM DOMAIN (JAZ) genes, which are the key repressors of the signaling pathway of the phytohormone jasmonic acid (JA). These observations suggest that the histone variant H3.3 promotes plant growth, including rosette growth and filament elongation.
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Affiliation(s)
- Xiaogang Long
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Wandong Yang
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Yanfang Lv
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Xiaoming Zhong
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Lin Chen
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Qingzhu Li
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Zhaopeng Lv
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Yanzhuo Li
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Yajun Cai
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Hongchun Yang
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
- RNA Institute, Wuhan University, Wuhan 430072, China
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4
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Vivek Hari Sundar G, Madhu A, Archana A, Shivaprasad PV. Plant histone variants at the nexus of chromatin readouts, stress and development. Biochim Biophys Acta Gen Subj 2024; 1868:130539. [PMID: 38072208 DOI: 10.1016/j.bbagen.2023.130539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 11/21/2023] [Accepted: 12/05/2023] [Indexed: 12/17/2023]
Abstract
Histones are crucial proteins that are involved in packaging the DNA as condensed chromatin inside the eukaryotic cell nucleus. Rather than being static packaging units, these molecules undergo drastic variations spatially and temporally to facilitate accessibility of DNA to replication, transcription as well as wide range of gene regulatory machineries. In addition, incorporation of paralogous variants of canonical histones in the chromatin is ascribed to specific functions. Given the peculiar requirement of plants to rapidly modulate gene expression levels on account of their sessile nature, histones and their variants serve as additional layers of gene regulation. This review summarizes the mechanisms and implications of distribution, modifications and differential incorporation of histones and their variants across plant genomes, and outlines emerging themes.
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Affiliation(s)
- G Vivek Hari Sundar
- National Centre for Biological Sciences, TIFR, GKVK Campus, Bangalore, India
| | - Aravind Madhu
- National Centre for Biological Sciences, TIFR, GKVK Campus, Bangalore, India; SASTRA University, Thirumalaisamudram, Thanjavur 613 401, India
| | - A Archana
- National Centre for Biological Sciences, TIFR, GKVK Campus, Bangalore, India; SASTRA University, Thirumalaisamudram, Thanjavur 613 401, India
| | - P V Shivaprasad
- National Centre for Biological Sciences, TIFR, GKVK Campus, Bangalore, India.
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5
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Liu K, Yin C, Ye W, Ma M, Wang Y, Wang P, Fang Y. Histone Variant H3.3 Controls Arabidopsis Fertility by Regulating Male Gamete Development. PLANT & CELL PHYSIOLOGY 2024; 65:68-78. [PMID: 37814936 DOI: 10.1093/pcp/pcad119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 09/13/2023] [Accepted: 10/01/2023] [Indexed: 10/11/2023]
Abstract
Reprograming of chromatin structures and changes in gene expression are critical for plant male gamete development, and epigenetic marks play an important role in these processes. Histone variant H3.3 is abundant in euchromatin and is largely associated with transcriptional activation. The precise function of H3.3 in gamete development remains unclear in plants. Here, we report that H3.3 is abundantly expressed in Arabidopsis anthers and its knockout mutant h3.3-1 is sterile due to male sterility. Transcriptome analysis of young inflorescence has identified 2348 genes downregulated in h3.3-1 mutant, among which 1087 target genes are directly bound by H3.3, especially at their 3' ends. As a group, this set of H3.3 targets is enriched in the reproduction-associated processes including male gamete generation, pollen sperm cell differentiation and pollen tube growth. The function of H3.3 in male gamete development is dependent on the Anti-Silencing Factor 1A/1B (ASF1A/1B)-Histone regulator A (HIRA)-mediated pathway. Our results suggest that ASF1A/1B-HIRA-mediated H3.3 deposition at its direct targets for transcription activation forms the regulatory networks responsible for male gamete development.
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Affiliation(s)
- Kunpeng Liu
- Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Chunmei Yin
- Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Wenjing Ye
- Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Min Ma
- Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yuanda Wang
- Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Pan Wang
- Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yuda Fang
- Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China
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6
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Jiang Z, Lozano-Durán R. Do plant histone variants stand idly by while DNA viruses invade the nucleus? STRESS BIOLOGY 2023; 3:46. [PMID: 37955829 PMCID: PMC10643808 DOI: 10.1007/s44154-023-00129-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 10/24/2023] [Indexed: 11/14/2023]
Affiliation(s)
- Zhihao Jiang
- Department of Plant Biochemistry, Center for Molecular Plant Biology (ZMBP), Eberhard-Karls University of Tübingen, Tübingen, Germany.
| | - Rosa Lozano-Durán
- Department of Plant Biochemistry, Center for Molecular Plant Biology (ZMBP), Eberhard-Karls University of Tübingen, Tübingen, Germany
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7
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Jiang D, Berger F. Variation is important: Warranting chromatin function and dynamics by histone variants. CURRENT OPINION IN PLANT BIOLOGY 2023; 75:102408. [PMID: 37399781 DOI: 10.1016/j.pbi.2023.102408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 05/24/2023] [Accepted: 06/01/2023] [Indexed: 07/05/2023]
Abstract
The chromatin of flowering plants exhibits a wide range of sequence variants of the core and linker histones. Recent studies have demonstrated that specific histone variant enrichment, combined with post-translational modifications (PTMs) of histones, defines distinct chromatin states that impact specific chromatin functions. Chromatin remodelers are emerging as key regulators of histone variant dynamics, contributing to shaping chromatin states and regulating gene transcription in response to environment. Recognizing the histone variants by their specific readers, controlled by histone PTMs, is crucial for maintaining genome and chromatin integrity. In addition, various histone variants have been shown to play essential roles in remodeling chromatin domains to facilitate important programmed transitions throughout the plant life cycle. In this review, we discuss recent findings in this exciting field of research, which holds immense promise for many surprising discoveries related to the evolution of complexity in plant organization through a seemingly simple protein family.
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Affiliation(s)
- Danhua Jiang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China.
| | - Frédéric Berger
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenter, Dr. Bohr-Gasse 3, 1030 Vienna, Austria.
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8
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Yang Q, Wang T, Cao J, Wang HL, Tan S, Zhang Y, Park S, Park H, Woo HR, Li X, Xia X, Guo H, Li Z. Histone variant HTB4 delays leaf senescence by epigenetic control of Ib bHLH transcription factor-mediated iron homeostasis. THE NEW PHYTOLOGIST 2023; 240:694-709. [PMID: 37265004 DOI: 10.1111/nph.19008] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 05/02/2023] [Indexed: 06/03/2023]
Abstract
Leaf senescence is an orderly process regulated by multiple internal factors and diverse environmental stresses including nutrient deficiency. Histone variants are involved in regulating plant growth and development. However, their functions and underlying regulatory mechanisms in leaf senescence remain largely unclear. Here, we found that H2B histone variant HTB4 functions as a negative regulator of leaf senescence. Loss of function of HTB4 led to early leaf senescence phenotypes that were rescued by functional complementation. RNA-seq analysis revealed that several Ib subgroup basic helix-loop-helix (bHLH) transcription factors (TFs) involved in iron (Fe) homeostasis, including bHLH038, bHLH039, bHLH100, and bHLH101, were suppressed in the htb4 mutant, thereby compromising the expressions of FERRIC REDUCTION OXIDASE 2 (FRO2) and IRON-REGULATED TRANSPORTER (IRT1), two important components of the Fe uptake machinery. Chromatin immunoprecipitation-quantitative polymerase chain reaction analysis revealed that HTB4 could bind to the promoter regions of Ib bHLH TFs and enhance their expression by promoting the enrichment of the active mark H3K4me3 near their transcriptional start sites. Moreover, overexpression of Ib bHLH TFs or IRT1 suppressed the premature senescence phenotype of the htb4 mutant. Our work established a signaling pathway, HTB4-bHLH TFs-FRO2/IRT1-Fe homeostasis, which regulates the onset and progression of leaf senescence.
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Affiliation(s)
- Qi Yang
- State Key Laboratory of Tree Genetics and Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, 100083, China
| | - Ting Wang
- State Key Laboratory of Tree Genetics and Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, 100083, China
| | - Jie Cao
- State Key Laboratory of Tree Genetics and Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, 100083, China
| | - Hou-Ling Wang
- State Key Laboratory of Tree Genetics and Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, 100083, China
| | - Shuya Tan
- State Key Laboratory of Tree Genetics and Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, 100083, China
| | - Yuan Zhang
- State Key Laboratory of Tree Genetics and Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, 100083, China
| | - Sanghoon Park
- Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, South Korea
| | - Hyunsoo Park
- Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, South Korea
| | - Hye Ryun Woo
- Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, South Korea
- New Biology Research Center, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, South Korea
| | - Xiaojuan Li
- State Key Laboratory of Tree Genetics and Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, 100083, China
| | - Xinli Xia
- State Key Laboratory of Tree Genetics and Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, 100083, China
| | - Hongwei Guo
- Department of Biology, Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Southern University of Science and Technology (SUSTech), Shenzhen, Guangdong, 518055, China
| | - Zhonghai Li
- State Key Laboratory of Tree Genetics and Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, 100083, China
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9
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Wu X, Zhang X, Huang B, Han J, Fang H. Advances in biological functions and mechanisms of histone variants in plants. Front Genet 2023; 14:1229782. [PMID: 37588047 PMCID: PMC10426802 DOI: 10.3389/fgene.2023.1229782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Accepted: 07/21/2023] [Indexed: 08/18/2023] Open
Abstract
Nucleosome is the basic subunit of chromatin, consisting of approximately 147bp DNA wrapped around a histone octamer, containing two copies of H2A, H2B, H3 and H4. A linker histone H1 can bind nucleosomes through its conserved GH1 domain, which may promote chromatin folding into higher-order structures. Therefore, the complexity of histones act importantly for specifying chromatin and gene activities. Histone variants, encoded by separate genes and characterized by only a few amino acids differences, can affect nucleosome packaging and stability, and then modify the chromatin properties. Serving as carriers of pivotal genetic and epigenetic information, histone variants have profound significance in regulating plant growth and development, response to both biotic and abiotic stresses. At present, the biological functions of histone variants in plant have become a research hotspot. Here, we summarize recent researches on the biological functions, molecular chaperons and regulatory mechanisms of histone variants in plant, and propose some novel research directions for further study of plant histone variants research field. Our study will provide some enlightens for studying and understanding the epigenetic regulation and chromatin specialization mediated by histone variant in plant.
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Affiliation(s)
- Xi Wu
- Jilin Province Engineering Laboratory of Plant Genetic Improvement, College of Plant Science, Jilin University, Changchun, China
| | - Xu Zhang
- Jilin Province Engineering Laboratory of Plant Genetic Improvement, College of Plant Science, Jilin University, Changchun, China
| | - Borong Huang
- Developmental Biology, Laboratory of Plant Molecular and Zhejiang A & F University, Hangzhou, China
| | - Junyou Han
- Jilin Province Engineering Laboratory of Plant Genetic Improvement, College of Plant Science, Jilin University, Changchun, China
| | - Huihui Fang
- Developmental Biology, Laboratory of Plant Molecular and Zhejiang A & F University, Hangzhou, China
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10
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Zhao F, Xue M, Zhang H, Li H, Zhao T, Jiang D. Coordinated histone variant H2A.Z eviction and H3.3 deposition control plant thermomorphogenesis. THE NEW PHYTOLOGIST 2023; 238:750-764. [PMID: 36647799 DOI: 10.1111/nph.18738] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Accepted: 01/11/2023] [Indexed: 06/17/2023]
Abstract
Plants can sense temperature changes and adjust their development and morphology accordingly in a process called thermomorphogenesis. This phenotypic plasticity implies complex mechanisms regulating gene expression reprogramming in response to environmental alteration. Histone variants often associate with specific chromatin states; yet, how their deposition/eviction modulates transcriptional changes induced by environmental cues remains elusive. In Arabidopsis thaliana, temperature elevation-induced transcriptional activation at thermo-responsive genes entails the chromatin eviction of a histone variant H2A.Z by INO80, which is recruited to these loci via interacting with a key thermomorphogenesis regulator PIF4. Here, we show that both INO80 and the deposition chaperones of another histone variant H3.3 associate with ELF7, a critical component of the transcription elongator PAF1 complex. H3.3 promotes thermomorphogenesis and the high temperature-enhanced RNA Pol II transcription at PIF4 targets, and it is broadly required for the H2A.Z removal-induced gene activation. Reciprocally, INO80 and ELF7 regulate H3.3 deposition, and are necessary for the high temperature-induced H3.3 enrichment at PIF4 targets. Our findings demonstrate close coordination between H2A.Z eviction and H3.3 deposition in gene activation induced by high temperature, and pinpoint the importance of histone variants dynamics in transcriptional regulation.
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Affiliation(s)
- Fengyue Zhao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100039, China
| | - Mande Xue
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100039, China
| | - Huairen Zhang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
| | - Hui Li
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100039, China
| | - Ting Zhao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
| | - Danhua Jiang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100039, China
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11
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Yang C, Zhu T, Zhou N, Huang S, Zeng Y, Jiang W, Xie Y, Shen WH, Li L. PIF7-mediated epigenetic reprogramming promotes the transcriptional response to shade in Arabidopsis. EMBO J 2023; 42:e111472. [PMID: 36912149 PMCID: PMC10106985 DOI: 10.15252/embj.2022111472] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 01/28/2023] [Accepted: 02/01/2023] [Indexed: 03/14/2023] Open
Abstract
For shade-intolerant plants, changes in light quality through competition from neighbors trigger shade avoidance syndrome (SAS): a series of morphological and physiological adaptations that are ultimately detrimental to plant health and crop yield. Phytochrome-interacting factor 7 (PIF7) is a major transcriptional regulator of SAS in Arabidopsis; however, how it regulates gene expression is not fully understood. Here, we show that PIF7 directly interacts with the histone chaperone anti-silencing factor 1 (ASF1). The ASF1-deprived asf1ab mutant showed defective shade-induced hypocotyl elongation. Histone regulator homolog A (HIRA), which mediates deposition of the H3.3 variant into chromatin, is also involved in SAS. RNA/ChIP-sequencing analyses identified the role of ASF1 in the direct regulation of a subset of PIF7 target genes. Furthermore, shade-elicited gene activation is accompanied by H3.3 enrichment, which is mediated by the PIF7-ASF1-HIRA regulatory module. Collectively, our data reveal that PIF7 recruits ASF1-HIRA to increase H3.3 incorporation into chromatin to promote gene transcription, thus enabling plants to effectively respond to environmental shade.
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Affiliation(s)
- Chuanwei Yang
- State Key Laboratory of Genetic Engineering, Institute of Plants Biology, School of Life Sciences, Fudan University, Shanghai, China
| | - Tongdan Zhu
- State Key Laboratory of Genetic Engineering, Institute of Plants Biology, School of Life Sciences, Fudan University, Shanghai, China
| | - Nana Zhou
- State Key Laboratory of Genetic Engineering, Department of Biochemistry, Institute of Plants Biology, School of Life Sciences, Fudan University, Shanghai, China
| | - Sha Huang
- State Key Laboratory of Genetic Engineering, Institute of Plants Biology, School of Life Sciences, Fudan University, Shanghai, China
| | - Yue Zeng
- State Key Laboratory of Genetic Engineering, Institute of Plants Biology, School of Life Sciences, Fudan University, Shanghai, China
| | - Wen Jiang
- State Key Laboratory of Genetic Engineering, Department of Biochemistry, Institute of Plants Biology, School of Life Sciences, Fudan University, Shanghai, China
| | - Yu Xie
- State Key Laboratory of Genetic Engineering, Institute of Plants Biology, School of Life Sciences, Fudan University, Shanghai, China
| | - Wen-Hui Shen
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
| | - Lin Li
- State Key Laboratory of Genetic Engineering, Institute of Plants Biology, School of Life Sciences, Fudan University, Shanghai, China
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12
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Wang Y, Li Y, Zhou F, Zhang L, Gong J, Cheng C, Chen J, Lou Q. Genome-wide characterization, phylogenetic and expression analysis of Histone gene family in cucumber (Cucumis sativus L.). Int J Biol Macromol 2023; 230:123401. [PMID: 36702227 DOI: 10.1016/j.ijbiomac.2023.123401] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 01/14/2023] [Accepted: 01/18/2023] [Indexed: 01/25/2023]
Abstract
Histones are essential components of chromatin and play an important role in regulating gene transcription and participating in DNA replication. Here, we performed a comprehensive analysis of this gene family. In this study, we identified 37 CsHistones that were classified into five groups (H1, H2A, H2B, H3 and H4). The closely linked subfamilies exhibited more similarity in terms of motifs and intron/exon numbers. Segmental duplication (SD) is the main driving force of cucumber CsHistones expansion. Analysis of cis-regulatory elements in the promoter region of CsHistones showed that CsHistones can respond to a variety of stresses. RNA-Seq analysis indicated that the expression of most CsHistones was associated with different stresses, including downy mildew, powdery mildew, wilt, heat, cold, salt stress, and waterlogging. Expression analysis showed that several genes of H3 group were highly expressed in different reproductive organs. Notably, CsCENH3 (CsHistone30) has the characteristics of a variant histone, and we demonstrated that CsCENH3 was localized on the nucleus and its proteins were expressed in centromere region. These findings provide valuable information for the identification and potential functions of Histone genes and ideas for the cultivation of CENH3-mediated haploid induction lines in cucumber.
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Affiliation(s)
- Yi Wang
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China
| | - Yangang Li
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China
| | - Fang Zhou
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China
| | - Lu Zhang
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China
| | - Jianlei Gong
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China
| | - Chunyan Cheng
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China
| | - Jinfeng Chen
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China
| | - Qunfeng Lou
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China.
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13
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Pan J, Zhang H, Zhan Z, Zhao T, Jiang D. A REF6-dependent H3K27me3-depleted state facilitates gene activation during germination in Arabidopsis. J Genet Genomics 2023; 50:178-191. [PMID: 36113770 DOI: 10.1016/j.jgg.2022.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 09/07/2022] [Indexed: 11/17/2022]
Abstract
Seed germination is a critical developmental switch from a quiescent state to active growth, which involves extensive changes in metabolism, gene expression, and cellular identity. However, our understanding of epigenetic and transcriptional reprogramming during this process is limited. The histone H3 lysine 27 trimethylation (H3K27me3) plays a key role in regulating gene repression and cell fate specification. Here, we profile H3K27me3 dynamics and dissect the function of H3K27 demethylation during germination in Arabidopsis. Our temporal genome-wide profiling of H3K27me3 and transcription reveals delayed H3K27me3 reprogramming compared with transcriptomic changes during germination, with H3K27me3 changes mainly occurring when the embryo is entering into vegetative development. RELATIVE OF EARLY FLOWERING 6 (REF6)-mediated H3K27 demethylation is necessary for robust germination but does not significantly contribute to H3K27me3 dynamics during germination, but rather stably establishes an H3K27me3-depleted state that facilitates the activation of hormone-related and expansin-coding genes important for germination. We also show that the REF6 chromatin occupancy is gradually established during germination to counteract increased Polycomb repressive complex 2 (PRC2). Our study provides key insights into the H3K27me3 dynamics during germination and suggests the function of H3K27me3 in facilitating cell fate switch. Furthermore, we reveal the importance of H3K27 demethylation-established transcriptional competence in gene activation during germination and likely other developmental processes.
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Affiliation(s)
- Jie Pan
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Huairen Zhang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhenping Zhan
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ting Zhao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China
| | - Danhua Jiang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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14
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Zhao T, Lu J, Zhang H, Xue M, Pan J, Ma L, Berger F, Jiang D. Histone H3.3 deposition in seed is essential for the post-embryonic developmental competence in Arabidopsis. Nat Commun 2022; 13:7728. [PMID: 36513677 PMCID: PMC9747979 DOI: 10.1038/s41467-022-35509-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 12/07/2022] [Indexed: 12/15/2022] Open
Abstract
The acquisition of germination and post-embryonic developmental ability during seed maturation is vital for seed vigor, an important trait for plant propagation and crop production. How seed vigor is established in seeds is still poorly understood. Here, we report the crucial function of Arabidopsis histone variant H3.3 in endowing seeds with post-embryonic developmental potentials. H3.3 is not essential for seed formation, but loss of H3.3 results in severely impaired germination and post-embryonic development. H3.3 exhibits a seed-specific 5' gene end distribution and facilitates chromatin opening at regulatory regions in seeds. During germination, H3.3 is essential for proper gene transcriptional regulation. Moreover, H3.3 is constantly loaded at the 3' gene end, correlating with gene body DNA methylation and the restriction of chromatin accessibility and cryptic transcription at this region. Our results suggest a fundamental role of H3.3 in initiating chromatin accessibility at regulatory regions in seed and licensing the embryonic to post-embryonic transition.
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Affiliation(s)
- Ting Zhao
- grid.9227.e0000000119573309State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
| | - Jingyun Lu
- grid.9227.e0000000119573309State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
| | - Huairen Zhang
- grid.9227.e0000000119573309State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
| | - Mande Xue
- grid.9227.e0000000119573309State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China ,grid.410726.60000 0004 1797 8419University of Chinese Academy of Sciences, Beijing, China
| | - Jie Pan
- grid.9227.e0000000119573309State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China ,grid.410726.60000 0004 1797 8419University of Chinese Academy of Sciences, Beijing, China
| | - Lijun Ma
- grid.9227.e0000000119573309State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China ,grid.410726.60000 0004 1797 8419University of Chinese Academy of Sciences, Beijing, China
| | - Frédéric Berger
- grid.24194.3a0000 0000 9669 8503Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenter, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Danhua Jiang
- grid.9227.e0000000119573309State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China ,grid.410726.60000 0004 1797 8419University of Chinese Academy of Sciences, Beijing, China
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15
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Chen Z, Li Z. Adaptation and integration of environmental cues to internal flowering network in Arabidopsis thaliana. REPRODUCTION AND BREEDING 2022. [DOI: 10.1016/j.repbre.2022.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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16
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Xu L, Cheng J, Jiang H. Mutation of histone H3 serine 28 to alanine influences H3K27me3-mediated gene silencing in Arabidopsis thaliana. PLANT PHYSIOLOGY 2022; 190:2417-2429. [PMID: 36053193 PMCID: PMC9706487 DOI: 10.1093/plphys/kiac409] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 07/19/2022] [Accepted: 08/02/2022] [Indexed: 06/15/2023]
Abstract
Histone modifications are essential for chromatin activity and play an important role in many biological processes. Trimethylation of histone H3K27 (H3K27me3) is a repressive modification established by Polycomb Repressive Complex 2 (PRC2). Although the presence of the histone H3 serine 28 phosphorylation (H3S28ph) modification at adjacent amino acid residues has both positive and negative effects on Polycomb silencing in mammals, little is known about the effect of H3S28ph on H3K27me3-mediated gene silencing in plants. In this study, we show that mutating H3S28A in Arabidopsis (Arabidopsis thaliana) causes a dominant-negative effect that leads to an early-flowering phenotype by promoting the expression of flowering-promoting genes independently of abnormal cell division. While H3S28ph levels decreased due to the H3S28A mutation, H3K27me3 levels at the same loci did not increase. Moreover, we observed decreased H3K27me3 levels at some known PRC2 target genes in H3.3S28A transgenic lines, rather than the expected enhanced H3K27me3-mediated silencing. In line with the reduced H3K27me3 levels, the expression of the PRC2 catalytic subunits CURLY LEAF and SWINGER decreased. Taken together, these data demonstrate that H3.3S28 is required for PRC2-dependent H3K27me3-mediated silencing in Arabidopsis, suggesting that H3S28 has a noncanonical function in H3K27me3-mediated gene silencing.
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Affiliation(s)
- Linhao Xu
- Leibniz Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany
| | - Jinping Cheng
- Leibniz Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany
| | - Hua Jiang
- Leibniz Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany
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17
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Probst AV. Deposition and eviction of histone variants define functional chromatin states in plants. CURRENT OPINION IN PLANT BIOLOGY 2022; 69:102266. [PMID: 35981458 DOI: 10.1016/j.pbi.2022.102266] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/30/2022] [Accepted: 06/28/2022] [Indexed: 06/15/2023]
Abstract
The organization of DNA with histone proteins into chromatin is fundamental for the regulation of gene expression. Incorporation of different histone variants into the nucleosome together with post-translational modifications of these histone variants allows modulating chromatin accessibility and contributes to the establishment of functional chromatin states either permissive or repressive for transcription. This review highlights emerging mechanisms required to deposit or evict histone variants in a timely and locus-specific manner. This review further discusses how assembly of specific histone variants permits to reinforce transmission of chromatin states during replication, to maintain heterochromatin organization and stability and to reprogram existing epigenetic information.
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Affiliation(s)
- Aline V Probst
- iGReD, CNRS, Inserm, Université Clermont Auvergne, 63000 Clermont-Ferrand, France.
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18
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Zhang H, Li X, Song R, Zhan Z, Zhao F, Li Z, Jiang D. Cap-binding complex assists RNA polymerase II transcription in plant salt stress response. PLANT, CELL & ENVIRONMENT 2022; 45:2780-2793. [PMID: 35773782 DOI: 10.1111/pce.14388] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 05/14/2022] [Accepted: 06/17/2022] [Indexed: 06/15/2023]
Abstract
Adaptive response to stress involves an extensive reprogramming of gene expression. Under stressful conditions, the induction of efficient changes in messenger RNA (mRNA) production is crucial for maximized plant survival. Transcription and pre-mRNA processing are two closely related steps in mRNA biogenesis, yet how they are controlled in plant stress response remains elusive. Here, we show that the Arabidopsis nuclear cap-binding complex (CBC) component CBP20 directly interacts with ELF7, a subunit of the transcription elongation factor RNA Pol II-associated factor 1 complex (PAF1c) to promote RNA Pol II transcription in plant response to salt stress. CBP20 and ELF7 coregulate the expression of a large number of genes including those crucial for salt tolerance. Both CBP20 and ELF7 are required for enhanced RNA Pol II elongation at salt-activated genes. Though CBP20 also regulates intron splicing, this function is largely independent of ELF7. Our study reveals the function of an RNA processing regulator CBC in assisting efficient RNA Pol II transcription and pinpoints the complex roles of CBC on mRNA production in plant salt stress resistance.
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Affiliation(s)
- Huairen Zhang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
| | - Xiaoyi Li
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Ruitian Song
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zhenping Zhan
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Fengyue Zhao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zicong Li
- Ministry of Education Key Laboratory of Plant Development and Environmental Adaption Biology, School of Life Sciences, Shandong University, Qingdao, China
| | - Danhua Jiang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
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19
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Kyung J, Jeon M, Lee I. Recent advances in the chromatin-based mechanism of FLOWERING LOCUS C repression through autonomous pathway genes. FRONTIERS IN PLANT SCIENCE 2022; 13:964931. [PMID: 36035698 PMCID: PMC9411803 DOI: 10.3389/fpls.2022.964931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 07/19/2022] [Indexed: 06/15/2023]
Abstract
Proper timing of flowering, a phase transition from vegetative to reproductive development, is crucial for plant fitness. The floral repressor FLOWERING LOCUS C (FLC) is the major determinant of flowering in Arabidopsis thaliana. In rapid-cycling A. thaliana accessions, which bloom rapidly, FLC is constitutively repressed by autonomous pathway (AP) genes, regardless of photoperiod. Diverse AP genes have been identified over the past two decades, and most of them repress FLC through histone modifications. However, the detailed mechanism underlying such modifications remains unclear. Several recent studies have revealed novel mechanisms to control FLC repression in concert with histone modifications. This review summarizes the latest advances in understanding the novel mechanisms by which AP proteins regulate FLC repression, including changes in chromatin architecture, RNA polymerase pausing, and liquid-liquid phase separation- and ncRNA-mediated gene silencing. Furthermore, we discuss how each mechanism is coupled with histone modifications in FLC chromatin.
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Affiliation(s)
- Jinseul Kyung
- School of Biological Sciences, Seoul National University, Seoul, South Korea
- Research Center for Plant Plasticity, Seoul National University, Seoul, South Korea
| | - Myeongjune Jeon
- School of Biological Sciences, Seoul National University, Seoul, South Korea
- Research Center for Plant Plasticity, Seoul National University, Seoul, South Korea
| | - Ilha Lee
- School of Biological Sciences, Seoul National University, Seoul, South Korea
- Research Center for Plant Plasticity, Seoul National University, Seoul, South Korea
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20
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Foroozani M, Holder DH, Deal RB. Histone Variants in the Specialization of Plant Chromatin. ANNUAL REVIEW OF PLANT BIOLOGY 2022; 73:149-172. [PMID: 35167758 PMCID: PMC9133179 DOI: 10.1146/annurev-arplant-070221-050044] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The basic unit of chromatin, the nucleosome, is an octamer of four core histone proteins (H2A, H2B, H3, and H4) and serves as a fundamental regulatory unit in all DNA-templated processes. The majority of nucleosome assembly occurs during DNA replication when these core histones are produced en masse to accommodate the nascent genome. In addition, there are a number of nonallelic sequence variants of H2A and H3 in particular, known as histone variants, that can be incorporated into nucleosomes in a targeted and replication-independent manner. By virtue of their sequence divergence from the replication-coupled histones, these histone variants can impart unique properties onto the nucleosomes they occupy and thereby influence transcription and epigenetic states, DNA repair, chromosome segregation, and other nuclear processes in ways that profoundly affect plant biology. In this review, we discuss the evolutionary origins of these variants in plants, their known roles in chromatin, and their impacts on plant development and stress responses. We focus on the individual and combined roles of histone variants in transcriptional regulation within euchromatic and heterochromatic genome regions. Finally, we highlight gaps in our understanding of plant variants at the molecular, cellular, and organismal levels, and we propose new directions for study in the field of plant histone variants.
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Affiliation(s)
| | - Dylan H Holder
- Department of Biology, Emory University, Atlanta, Georgia, USA;
- Graduate Program in Genetics and Molecular Biology, Emory University, Atlanta, Georgia, USA
| | - Roger B Deal
- Department of Biology, Emory University, Atlanta, Georgia, USA;
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