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Kobayashi NI, Takagi H, Yang X, Nishizawa-Yokoi A, Segawa T, Hoshina T, Oonishi T, Suzuki H, Iwata R, Toki S, Nakanishi TM, Tanoi K. Mutations in RZF1, a zinc-finger protein, reduce magnesium uptake in roots and translocation to shoots in rice. PLANT PHYSIOLOGY 2023; 192:342-355. [PMID: 36718554 PMCID: PMC10152673 DOI: 10.1093/plphys/kiad051] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 01/04/2023] [Accepted: 01/04/2023] [Indexed: 05/03/2023]
Abstract
Magnesium (Mg) homeostasis is critical for maintaining many biological processes, but little information is available to comprehend the molecular mechanisms regulating Mg concentration in rice (Oryza sativa). To make up for the lack of information, we aimed to identify mutants defective in Mg homeostasis through a forward genetic approach. As a result of the screening of 2,825 M2 seedlings mutated by ion-beam irradiation, we found a rice mutant that showed reduced Mg content in leaves and slightly increased Mg content in roots. Radiotracer 28Mg experiments showed that this mutant, named low-magnesium content 1 (LMGC1), has decreased Mg2+ influx in the root and Mg2+ translocation from root to shoot. Consequently, LMGC1 is sensitive to the low Mg condition and prone to develop chlorosis in the young mature leaf. The MutMap method identified a 7.4-kbp deletion in the LMGC1 genome leading to a loss of two genes. Genome editing using CRISPR-Cas9 further revealed that one of the two lost genes, a gene belonging to the RanBP2-type zinc-finger family that we named RanBP2-TYPE ZINC FINGER1 (OsRZF1), was the causal gene of the low Mg phenotype. OsRZF1 is a nuclear protein and may have a fundamental role in maintaining Mg homeostasis in rice plants.
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Affiliation(s)
- Natsuko I Kobayashi
- Graduate School of Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Hiroki Takagi
- Faculty of Bioresources and Environmental Sciences, Ishikawa Prefectural University, 1-308 Suematsu, Nonoichi, Ishikawa 921-8836, Japan
| | - Xiaoyu Yang
- Graduate School of Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Ayako Nishizawa-Yokoi
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), 3-1-3 Kannondai, Tsukuba 305-8604, Japan
| | - Tenta Segawa
- Faculty of Bioresources and Environmental Sciences, Ishikawa Prefectural University, 1-308 Suematsu, Nonoichi, Ishikawa 921-8836, Japan
| | - Tatsuaki Hoshina
- Graduate School of Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Takayuki Oonishi
- Center for Education and Research of Community Collaboration, Utsunomiya University, Utsunomiya 321-8505, Japan
| | - Hisashi Suzuki
- National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Ren Iwata
- Cyclotron and Radioisotope Center (CYRIC), Tohoku University, 6-3 Aramaki Aza-Aoba, Aoba-ku, Sendai 980-8572, Japan
| | - Seiichi Toki
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), 3-1-3 Kannondai, Tsukuba 305-8604, Japan
- Faculty of Agriculture, Ryukoku University, 1-5 Yokotani, Seta Oe-cho, Otsu, Shiga 520-2194, Japan
- Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Yokohama, Kanagawa 236-0027, Japan
| | - Tomoko M Nakanishi
- Graduate School of Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
- Hoshi University, 2-4-41 Ebara, Shinagawa-Ku, Tokyo 142-8501, Japan
| | - Keitaro Tanoi
- Graduate School of Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
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Clarkson DT, Williams L, Hanson JB. Perfusion of onion root xylem vessels: a method and some evidence of control of the pH of the xylem sap. PLANTA 1984; 162:361-369. [PMID: 24253171 DOI: 10.1007/bf00396749] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/1984] [Accepted: 05/08/1984] [Indexed: 06/02/2023]
Abstract
We describe a method for perfusing the xylem in the stele of excised onion roots with solutions of known composition under a pressure gradient. Tracer studies using [(14)C] polyethylene glycol 4000 and the fluorescent dye, Tinopal CBSX, indicated that perfusing solutions passed exclusively through the xylem vessels. The conductance of the xylem was small over the apical 100 mm of the root axis but increased markedly between 100 and 200 mm. Unbuffered perfusion solutions supplied in the range pH 3.7-7.8 emerged after passage through the xylem adjusted to pH 5.2-6.0, indicating the presence of mechanisms for absorbing or releasing protons. This adjustment continued over many hours with net proton fluxes apparently determined by the disparity between the pH of the perfusion solution and the usual xylem sap pH of about 5.5. Mild acidification of the xylem sap by buffered perfusion solutions increased the release of (86)Rb (K(+)) and (35)SO4 (2-) from the stelar tissue into the xylem stream. The ion-transporting properties of onion roots seemed little changed by excision from the bulbs, or by removal of the apical zones of the root axis. The pH of sap produced by root pressure resembles that found in the outflow solutions of perfused root segments.
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Affiliation(s)
- D T Clarkson
- Letcombe Laboratory, Agricultural Research Council, Wantage, OX12 9JT, Oxon, UK
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