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Dietrich D, Pang L, Kobayashi A, Fozard JA, Boudolf V, Bhosale R, Antoni R, Nguyen T, Hiratsuka S, Fujii N, Miyazawa Y, Bae TW, Wells DM, Owen MR, Band LR, Dyson RJ, Jensen OE, King JR, Tracy SR, Sturrock CJ, Mooney SJ, Roberts JA, Bhalerao RP, Dinneny JR, Rodriguez PL, Nagatani A, Hosokawa Y, Baskin TI, Pridmore TP, De Veylder L, Takahashi H, Bennett MJ. Root hydrotropism is controlled via a cortex-specific growth mechanism. NATURE PLANTS 2017; 3:17057. [PMID: 28481327 DOI: 10.1038/nplants.2017.57] [Citation(s) in RCA: 142] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 03/23/2017] [Indexed: 05/24/2023]
Abstract
Plants can acclimate by using tropisms to link the direction of growth to environmental conditions. Hydrotropism allows roots to forage for water, a process known to depend on abscisic acid (ABA) but whose molecular and cellular basis remains unclear. Here we show that hydrotropism still occurs in roots after laser ablation removed the meristem and root cap. Additionally, targeted expression studies reveal that hydrotropism depends on the ABA signalling kinase SnRK2.2 and the hydrotropism-specific MIZ1, both acting specifically in elongation zone cortical cells. Conversely, hydrotropism, but not gravitropism, is inhibited by preventing differential cell-length increases in the cortex, but not in other cell types. We conclude that root tropic responses to gravity and water are driven by distinct tissue-based mechanisms. In addition, unlike its role in root gravitropism, the elongation zone performs a dual function during a hydrotropic response, both sensing a water potential gradient and subsequently undergoing differential growth.
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Affiliation(s)
- Daniela Dietrich
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Lei Pang
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Akie Kobayashi
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - John A Fozard
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
| | - Véronique Boudolf
- Department of Plant Biotechnology and Bioinformatics, Ghent University, (Technologiepark 927), 9052 Ghent, Belgium
- VIB Center for Plant Systems Biology, (Technologiepark 927), 9052 Ghent, Belgium
| | - Rahul Bhosale
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
- Department of Plant Biotechnology and Bioinformatics, Ghent University, (Technologiepark 927), 9052 Ghent, Belgium
- VIB Center for Plant Systems Biology, (Technologiepark 927), 9052 Ghent, Belgium
| | - Regina Antoni
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
| | - Tuan Nguyen
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- School of Computer Science, University of Nottingham, Nottingham NG8 1BB, UK
| | - Sotaro Hiratsuka
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Nobuharu Fujii
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Yutaka Miyazawa
- Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
| | - Tae-Woong Bae
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Darren M Wells
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Markus R Owen
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Centre for Mathematical Medicine &Biology, University of Nottingham, Nottingham NG7 2RD, UK
| | - Leah R Band
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Centre for Mathematical Medicine &Biology, University of Nottingham, Nottingham NG7 2RD, UK
| | - Rosemary J Dyson
- School of Mathematics, University of Birmingham, Birmingham B15 2TT, UK
| | - Oliver E Jensen
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- School of Mathematics, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - John R King
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Centre for Mathematical Medicine &Biology, University of Nottingham, Nottingham NG7 2RD, UK
| | - Saoirse R Tracy
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Craig J Sturrock
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Sacha J Mooney
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Jeremy A Roberts
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Rishikesh P Bhalerao
- Department of Forest Genetics and Plant Physiology, SLU, S-901 83 Umea, Sweden
- College of Science, KSU, Riyadh, Saudi Arabia
| | - José R Dinneny
- Department of Plant Biology, Carnegie Institution for Science, 260 Panama Street, Stanford, California 94305, USA
| | - Pedro L Rodriguez
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Cientificas-Universidad Politecnica de Valencia, ES-46022 Valencia, Spain
| | - Akira Nagatani
- Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yoichiroh Hosokawa
- Graduate School of Materials Science, Nara Institute of Science &Technology, Ikoma 630-0101, Japan
| | - Tobias I Baskin
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Biology Department, University of Massachusetts, Amherst, Massachusetts 01003-9297, USA
| | - Tony P Pridmore
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- School of Computer Science, University of Nottingham, Nottingham NG8 1BB, UK
| | - Lieven De Veylder
- Department of Plant Biotechnology and Bioinformatics, Ghent University, (Technologiepark 927), 9052 Ghent, Belgium
- VIB Center for Plant Systems Biology, (Technologiepark 927), 9052 Ghent, Belgium
| | - Hideyuki Takahashi
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Malcolm J Bennett
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
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Wegner LH. A pump/leak model of growth: the biophysics of cell elongation in higher plants revisited. FUNCTIONAL PLANT BIOLOGY : FPB 2017; 44:185-197. [PMID: 32480556 DOI: 10.1071/fp16184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 09/08/2016] [Indexed: 06/11/2023]
Abstract
Current concepts of growth hydraulics in higher plants are critically revisited, and it is concluded that they partly fail to interpret the experimental data adequately, particularly in the case of hydroponics-grown roots. Theoretical considerations indicate that the growth rate in roots is controlled by the extensibility of the cell wall, excluding water availability (i.e. hydraulic conductance) as a major constraint. This is supported by the findings that the growth rate does not scale with turgor, and that no radial nor axial water potential gradients have been observed in the root elongation zone. Nevertheless, a water potential deficit ranging from -0.2 to -0.6MPa has repeatedly been reported for growing cells that by far exceeds the shallow trans-membrane water potential difference required for the uptake of growth water. Unexpectedly, growth was also shown to depend on the hydraulic conductance (LP) of the plasma membrane of root cells, even though LP should generally be too large to have an impact on growth. For leaves, similar observations have been reported, but the interpretation of the data is less straightforward. Inconsistencies associated with the current model of growth hydraulics prompt the author to suggest a revised model that comprises, in addition to a passive mechanism of water transport across the plasma membrane of growing cells mediated by aquaporins ('leak') a secondary active water transport ('pump'), in analogy to a mechanism previously demonstrated for mammalian epithelia and postulated for xylem parenchyma cells in roots. Water is hypothesised to be secreted against a trans-membrane water potential difference by cotransport with solutes (salts, sugars, and/or amino acids), taking advantage of the free energy released by this transport step. The solute concentration gradient is supposed to be maintained by a subsequent retrieval of the solutes from the apoplast and back-transport at the expense of metabolic energy. Water secretion tends to reduce the turgor pressure and retards growth, but turgor and, in turn, growth can be upregulated very rapidly independent from any adjustment in the osmolyte deposition rate by increasing LP and/or reducing secondary active water transport, e.g. when the root is exposed to mild osmotic stress, as confirmed by experimental studies.
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Affiliation(s)
- Lars H Wegner
- Karlsruhe Institute of Technology, Institute for Pulsed Power and Microwave Technology (IHM), Campus North, Building 630, Hermann v. Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany. Email
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