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Voothuluru P, Wu Y, Sharp RE. Not so hidden anymore: Advances and challenges in understanding root growth under water deficits. THE PLANT CELL 2024; 36:1377-1409. [PMID: 38382086 PMCID: PMC11062450 DOI: 10.1093/plcell/koae055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 02/09/2024] [Accepted: 02/15/2024] [Indexed: 02/23/2024]
Abstract
Limited water availability is a major environmental factor constraining plant development and crop yields. One of the prominent adaptations of plants to water deficits is the maintenance of root growth that enables sustained access to soil water. Despite early recognition of the adaptive significance of root growth maintenance under water deficits, progress in understanding has been hampered by the inherent complexity of root systems and their interactions with the soil environment. We highlight selected milestones in the understanding of root growth responses to water deficits, with emphasis on founding studies that have shaped current knowledge and set the stage for further investigation. We revisit the concept of integrated biophysical and metabolic regulation of plant growth and use this framework to review central growth-regulatory processes occurring within root growth zones under water stress at subcellular to organ scales. Key topics include the primary processes of modifications of cell wall-yielding properties and osmotic adjustment, as well as regulatory roles of abscisic acid and its interactions with other hormones. We include consideration of long-recognized responses for which detailed mechanistic understanding has been elusive until recently, for example hydrotropism, and identify gaps in knowledge, ongoing challenges, and opportunities for future research.
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Affiliation(s)
- Priya Voothuluru
- Division of Plant Science and Technology, University of Missouri, Columbia, MO 65211, USA
- Interdisciplinary Plant Group, University of Missouri, Columbia, MO 65211, USA
| | - Yajun Wu
- Department of Biology and Microbiology, South Dakota State University, Brookings, SD 57007, USA
| | - Robert E Sharp
- Division of Plant Science and Technology, University of Missouri, Columbia, MO 65211, USA
- Interdisciplinary Plant Group, University of Missouri, Columbia, MO 65211, USA
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2
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Li C, Li X, Deng Z, Song Y, Liu X, Tang XA, Li Z, Zhang Y, Zhang B, Tang W, Shang JX, Sun Y. EGR1 and EGR2 positively regulate plant ABA signaling by modulating the phosphorylation of SnRK2.2. THE NEW PHYTOLOGIST 2024; 241:1492-1509. [PMID: 38095247 DOI: 10.1111/nph.19458] [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: 02/10/2023] [Accepted: 11/17/2023] [Indexed: 01/26/2024]
Abstract
During abscisic acid (ABA) signaling, reversible phosphorylation controls the activity and accumulation of class III SNF1-RELATED PROTEIN KINASE 2s (SnRK2s). While protein phosphatases that negatively regulate SnRK2s have been identified, those that positively regulate ABA signaling through SnRK2s are less understood. In this study, Arabidopsis thaliana mutants of Clade E Growth-Regulating 1 and 2 (EGR1/2), which belong to the protein phosphatase 2C family, exhibited reduced ABA sensitivity in terms of seed germination, cotyledon greening, and ABI5 accumulation. Conversely, overexpression increased these ABA-induced responses. Transcriptomic data revealed that most ABA-regulated genes in egr1 egr2 plants were expressed at reduced levels compared with those in Col-0 after ABA treatment. Abscisic acid up-regulated EGR1/2, which interact directly with SnRK2.2 through its C-terminal domain I. Genetic analysis demonstrated that EGR1/2 function through SnRK2.2 during ABA response. Furthermore, SnRK2.2 de-phosphorylation by EGR1/2 was identified at serine 31 within the ATP-binding pocket. A phospho-mimic mutation confirmed that phosphorylation at serine 31 inhibited SnRK2.2 activity and reduced ABA responsiveness in plants. Our findings highlight the positive role of EGR1/2 in regulating ABA signaling, they reveal a new mechanism for modulating SnRK2.2 activity, and provide novel insight into how plants fine-tune their responses to ABA.
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Affiliation(s)
- Chuanling Li
- Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Research Center of the Basic Discipline of Cell Biology, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China
- Key Laboratory of Tropical Fruit Biology, Ministry of Agriculture and Rural Affairs, South Subtropical Crops Research Institute, Chinese Academy of Tropical Agricultural Sciences, Zhanjiang, 524091, China
| | - Xuetong Li
- Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Research Center of the Basic Discipline of Cell Biology, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China
| | - Zhiping Deng
- Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021, China
| | - Yuning Song
- Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Research Center of the Basic Discipline of Cell Biology, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China
| | - Xinye Liu
- Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Research Center of the Basic Discipline of Cell Biology, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China
| | - Xiaohan Alex Tang
- Division of Life Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong Special Administrative Region, China
| | - Ziye Li
- Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Research Center of the Basic Discipline of Cell Biology, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China
| | - Ya Zhang
- Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Research Center of the Basic Discipline of Cell Biology, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China
| | - Baowen Zhang
- Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Research Center of the Basic Discipline of Cell Biology, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China
| | - Wenqiang Tang
- Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Research Center of the Basic Discipline of Cell Biology, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China
| | - Jian-Xiu Shang
- Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Research Center of the Basic Discipline of Cell Biology, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China
| | - Yu Sun
- Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Research Center of the Basic Discipline of Cell Biology, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China
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3
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Fu X, Zhong L, Wang H, He H, Chen X. Elucidation of the Mechanism of Rapid Growth Recovery in Rice Seedlings after Exposure to Low-Temperature Low-Light Stress: Analysis of Rice Root Transcriptome, Metabolome, and Physiology. Int J Mol Sci 2023; 24:17359. [PMID: 38139187 PMCID: PMC10743590 DOI: 10.3390/ijms242417359] [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: 10/26/2023] [Revised: 12/05/2023] [Accepted: 12/08/2023] [Indexed: 12/24/2023] Open
Abstract
Late spring cold is a disastrous weather condition that often affects early rice seedlings in southern China, limiting the promotion of direct seeding cultivation. However, there are few reports on the effect of these events and on the growth recovery mechanism of rice root systems after rice seedlings are exposed to this stress. This study selected the strong-growth-recovery variety B116 (R310/R974, F17) and the slow-recovery variety B811 (Zhonghui 286) for direct seeding cultivation and exposed them to low temperature and low-light stress to simulate a late spring cold event in an artificial climate chamber. The treatment consisted of 4 days of exposure to a day/night temperature of 14/10 °C and a light intensity of 266 µmol m-2s-1 while the control group was kept at a day/night temperature of 27/25 °C and light intensity of 533 µmol m-2s-1. The results showed that 6 days after stress, the total length, surface area, and volume of B116 roots increased by 335.5%, 290.1%, and 298.5%, respectively, while those of B811 increased by 228.8%, 262.0%, and 289.1%, respectively. In B116, the increase in root fresh weight was 223.1%, and that in B811 was 165.6%, demonstrating rapid root recovery after stress and significant differences among genotypes. The content of H2O2 and MDA in the B116 roots decreased faster than that in the B811 roots after normal light intensity and temperature conditions were restored, and the activity of ROS metabolism enzymes was stronger in B116 roots than in B811 roots. The correlation analysis between the transcriptome and metabolome showed that endogenous signal transduction and starch and sucrose metabolism were the main metabolic pathways affecting the rapid growth of rice seedling roots after exposure to combined stress from low temperature and low light intensities. The levels of auxin and sucrose in the roots of the strong-recovery variety B116 were higher, and this variety's metabolism was downregulated significantly faster than that of B811. The auxin response factor and sucrose synthesis-related genes SPS1 and SUS4 were significantly upregulated. This study contributes to an understanding of the rapid growth recovery mechanism in rice after exposure to combined stress from low-temperature and low-light conditions.
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Affiliation(s)
| | | | | | | | - Xiaorong Chen
- Key Laboratory of Crop Physiology, Ecology and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China; (X.F.); (L.Z.); (H.W.); (H.H.)
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4
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Zhu L, Wang H, Zhu J, Wang X, Jiang B, Hou L, Xiao G. A conserved brassinosteroid-mediated BES1-CERP-EXPA3 signaling cascade controls plant cell elongation. Cell Rep 2023; 42:112301. [PMID: 36952343 DOI: 10.1016/j.celrep.2023.112301] [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: 10/07/2022] [Revised: 02/05/2023] [Accepted: 03/06/2023] [Indexed: 03/24/2023] Open
Abstract
Continuous plant growth is achieved by cell division and cell elongation. Brassinosteroids control cell elongation and differentiation throughout plant life. However, signaling cascades underlying BR-mediated cell elongation are unknown. In this study, we introduce cotton fiber, one of the most representative single-celled tissues, to decipher cell-specific BR signaling. We find that gain of function of GhBES1, a key transcriptional activator in BR signaling, enhances fiber elongation. The chromatin immunoprecipitation sequencing analysis identifies a cell-elongation-related protein, GhCERP, whose transcription is directly activated by GhBES1. GhCERP, a downstream target of GhBES1, transmits the GhBES1-mediated BR signaling to its target gene, GhEXPA3-1. Ultimately, GhEXPA3-1 promotes fiber cell elongation. In addition, inter-species functional analysis of the BR-mediated BES1-CERP-EXPA3 signaling cascade also promotes Arabidopsis root and hypocotyl growth. We propose that the BES1-CERP-EXPA3 module may be a broad-spectrum pathway that is universally exploited by diverse plant species to regulate BR-promoted cell elongation.
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Affiliation(s)
- Liping Zhu
- College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China
| | - Huiqin Wang
- College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China
| | - Jiaojie Zhu
- College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China
| | - Xiaosi Wang
- College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China
| | - Bin Jiang
- College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China
| | - Liyong Hou
- College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China
| | - Guanghui Xiao
- College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China.
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5
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Nolan TM, Vukašinović N, Hsu CW, Zhang J, Vanhoutte I, Shahan R, Taylor IW, Greenstreet L, Heitz M, Afanassiev A, Wang P, Szekely P, Brosnan A, Yin Y, Schiebinger G, Ohler U, Russinova E, Benfey PN. Brassinosteroid gene regulatory networks at cellular resolution in the Arabidopsis root. Science 2023; 379:eadf4721. [PMID: 36996230 PMCID: PMC10119888 DOI: 10.1126/science.adf4721] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 02/09/2023] [Indexed: 04/01/2023]
Abstract
Brassinosteroids are plant steroid hormones that regulate diverse processes, such as cell division and cell elongation, through gene regulatory networks that vary in space and time. By using time series single-cell RNA sequencing to profile brassinosteroid-responsive gene expression specific to different cell types and developmental stages of the Arabidopsis root, we identified the elongating cortex as a site where brassinosteroids trigger a shift from proliferation to elongation associated with increased expression of cell wall-related genes. Our analysis revealed HOMEOBOX FROM ARABIDOPSIS THALIANA 7 (HAT7) and GT-2-LIKE 1 (GTL1) as brassinosteroid-responsive transcription factors that regulate cortex cell elongation. These results establish the cortex as a site of brassinosteroid-mediated growth and unveil a brassinosteroid signaling network regulating the transition from proliferation to elongation, which illuminates aspects of spatiotemporal hormone responses.
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Affiliation(s)
| | - Nemanja Vukašinović
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- Center for Plant Systems Biology, VIB, Ghent, Belgium
| | - Che-Wei Hsu
- Department of Biology, Duke University, Durham, NC, USA
- Department of Biology, Humboldt Universitat zu Berlin, Berlin, Germany
- The Berlin Institute for Medical Systems Biology, Max Delbruck Center for Molecular Medicine, Berlin, Germany
| | | | - Isabelle Vanhoutte
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- Center for Plant Systems Biology, VIB, Ghent, Belgium
| | - Rachel Shahan
- Department of Biology, Duke University, Durham, NC, USA
- Howard Hughes Medical Institute, Duke University, Durham, NC, USA
| | | | - Laura Greenstreet
- Department of Mathematics, University of British Columbia, Vancouver, BC, Canada
| | - Matthieu Heitz
- Department of Mathematics, University of British Columbia, Vancouver, BC, Canada
| | - Anton Afanassiev
- Department of Mathematics, University of British Columbia, Vancouver, BC, Canada
| | - Ping Wang
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, USA
| | - Pablo Szekely
- Department of Biology, Duke University, Durham, NC, USA
- Howard Hughes Medical Institute, Duke University, Durham, NC, USA
| | - Aiden Brosnan
- Department of Biology, Duke University, Durham, NC, USA
| | - Yanhai Yin
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, USA
| | - Geoffrey Schiebinger
- Department of Mathematics, University of British Columbia, Vancouver, BC, Canada
| | - Uwe Ohler
- Department of Biology, Humboldt Universitat zu Berlin, Berlin, Germany
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, USA
- Department of Computer Science, Humboldt Universitat zu Berlin, Berlin, Germany
| | - Eugenia Russinova
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- Center for Plant Systems Biology, VIB, Ghent, Belgium
| | - Philip N Benfey
- Department of Biology, Duke University, Durham, NC, USA
- Howard Hughes Medical Institute, Duke University, Durham, NC, USA
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6
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Verslues PE, Bailey-Serres J, Brodersen C, Buckley TN, Conti L, Christmann A, Dinneny JR, Grill E, Hayes S, Heckman RW, Hsu PK, Juenger TE, Mas P, Munnik T, Nelissen H, Sack L, Schroeder JI, Testerink C, Tyerman SD, Umezawa T, Wigge PA. Burning questions for a warming and changing world: 15 unknowns in plant abiotic stress. THE PLANT CELL 2023; 35:67-108. [PMID: 36018271 PMCID: PMC9806664 DOI: 10.1093/plcell/koac263] [Citation(s) in RCA: 39] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 08/21/2022] [Indexed: 05/08/2023]
Abstract
We present unresolved questions in plant abiotic stress biology as posed by 15 research groups with expertise spanning eco-physiology to cell and molecular biology. Common themes of these questions include the need to better understand how plants detect water availability, temperature, salinity, and rising carbon dioxide (CO2) levels; how environmental signals interface with endogenous signaling and development (e.g. circadian clock and flowering time); and how this integrated signaling controls downstream responses (e.g. stomatal regulation, proline metabolism, and growth versus defense balance). The plasma membrane comes up frequently as a site of key signaling and transport events (e.g. mechanosensing and lipid-derived signaling, aquaporins). Adaptation to water extremes and rising CO2 affects hydraulic architecture and transpiration, as well as root and shoot growth and morphology, in ways not fully understood. Environmental adaptation involves tradeoffs that limit ecological distribution and crop resilience in the face of changing and increasingly unpredictable environments. Exploration of plant diversity within and among species can help us know which of these tradeoffs represent fundamental limits and which ones can be circumvented by bringing new trait combinations together. Better defining what constitutes beneficial stress resistance in different contexts and making connections between genes and phenotypes, and between laboratory and field observations, are overarching challenges.
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Affiliation(s)
| | - Julia Bailey-Serres
- Department of Botany and Plant Sciences, Center for Plant Cell Biology, University of California, Riverside, California 92521, USA
| | - Craig Brodersen
- School of the Environment, Yale University, New Haven, Connecticut 06511, USA
| | - Thomas N Buckley
- Department of Plant Sciences, University of California, Davis, California 95616, USA
| | - Lucio Conti
- Department of Biosciences, University of Milan, Milan 20133, Italy
| | - Alexander Christmann
- School of Life Sciences, Technical University Munich, Freising-Weihenstephan 85354, Germany
| | - José R Dinneny
- Department of Biology, Stanford University, Stanford, California 94305, USA
| | - Erwin Grill
- School of Life Sciences, Technical University Munich, Freising-Weihenstephan 85354, Germany
| | - Scott Hayes
- Laboratory of Plant Physiology, Plant Sciences Group, Wageningen University and Research, Wageningen 6708 PB, The Netherlands
| | - Robert W Heckman
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas 78712, USA
| | - Po-Kai Hsu
- Department of Cell and Developmental Biology, School of Biological Sciences, University of California San Diego, La Jolla, California 92093, USA
| | - Thomas E Juenger
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas 78712, USA
| | - Paloma Mas
- Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Barcelona 08193, Spain
- Consejo Superior de Investigaciones Científicas (CSIC), Barcelona 08028, Spain
| | - Teun Munnik
- Department of Plant Cell Biology, Green Life Sciences Cluster, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam NL-1098XH, The Netherlands
| | - Hilde Nelissen
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent 9052, Belgium
- VIB Center for Plant Systems Biology, Ghent 9052, Belgium
| | - Lawren Sack
- Department of Ecology and Evolutionary Biology, Institute of the Environment and Sustainability, University of California, Los Angeles, California 90095, USA
| | - Julian I Schroeder
- Department of Cell and Developmental Biology, School of Biological Sciences, University of California San Diego, La Jolla, California 92093, USA
| | - Christa Testerink
- Laboratory of Plant Physiology, Plant Sciences Group, Wageningen University and Research, Wageningen 6708 PB, The Netherlands
| | - Stephen D Tyerman
- ARC Center Excellence, Plant Energy Biology, School of Agriculture Food and Wine, University of Adelaide, Adelaide, South Australia 5064, Australia
| | - Taishi Umezawa
- Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 6708 PB, Japan
| | - Philip A Wigge
- Leibniz-Institut für Gemüse- und Zierpflanzenbau, Großbeeren 14979, Germany
- Institute of Biochemistry and Biology, University of Potsdam, Potsdam 14476, Germany
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7
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Juenger TE, Verslues PE. Time for a drought experiment: Do you know your plants' water status? THE PLANT CELL 2023; 35:10-23. [PMID: 36346190 PMCID: PMC9806650 DOI: 10.1093/plcell/koac324] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 11/03/2022] [Indexed: 06/16/2023]
Abstract
Drought stress is an increasing concern because of climate change and increasing demands on water for agriculture. There are still many unknowns about how plants sense and respond to water limitation, including which genes and cellular mechanisms are impactful for ecology and crop improvement in drought-prone environments. A better understanding of plant drought resistance will require integration of several research disciplines. A common set of parameters to describe plant water status and quantify drought severity can enhance data interpretation and research integration across the research disciplines involved in understanding drought resistance and would be especially useful in integrating the flood of genomic data being generated in drought studies. Water potential (ψw) is a physical measure of the free energy status of water that, along with related physiological measurements, allows unambiguous description of plant water status that can apply across various soil types and environmental conditions. ψw and related physiological parameters can be measured with relatively modest investment in equipment and effort. Thus, we propose that increased use of ψw as a fundamental descriptor of plant water status can enhance the insight gained from many drought-related experiments and facilitate data integration and sharing across laboratories and research disciplines.
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Verslues PE, Longkumer T. Size and activity of the root meristem: A key for drought resistance and a key model of drought-related signaling. PHYSIOLOGIA PLANTARUM 2022; 174:e13622. [PMID: 34988997 DOI: 10.1111/ppl.13622] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 12/17/2021] [Accepted: 12/24/2021] [Indexed: 06/14/2023]
Abstract
Plants make many adjustments to their growth and development in response to even small changes in water availability. Under such conditions, root elongation can be actively restricted by stress-related signaling mechanisms. Here we look at how the Arabidopsis thaliana root meristem can be affected by moderate water limitation (low water potential, ψw ). Recent characterization of the clade E Growth-Regulating (EGR) protein phosphatases and Microtubule Associated Stress Protein 1 (MASP1) provides an example of how active restriction of root meristem size allows the plant to downregulate root elongation during low ψw stress. EGR2 protein accumulation in cortex cells of the transition zone at the distal end of the root meristem illustrates how the balance of cell division versus cell expansion signals at this critical location can determine meristem size and root elongation during low ψw . These characteristics of EGRs also raise the question of whether they may also be involved in hydrotropism, and, more broadly, whether hydrotropism is a distinct response or a specific manifestation of more general mechanisms used to adjust root growth under moderate severity low ψw whether or not a gradient of water availability is present. These questions, as well as a better understanding of how specific cell layers (cortex and endodermis) seem to have an outsized role in growth regulation and better understanding the roles of plasma membrane-based signaling and polar-localized proteins in the regulation of root meristem size and cell division activity are key to elucidating the cellular mechanisms that determine root growth behavior during soil drying.
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Affiliation(s)
- Paul E Verslues
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
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