1
|
Oburger E, Schmidt H, Staudinger C. Harnessing belowground processes for sustainable intensification of agricultural systems. PLANT AND SOIL 2022; 478:177-209. [PMID: 36277079 PMCID: PMC9579094 DOI: 10.1007/s11104-022-05508-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 05/18/2022] [Indexed: 06/16/2023]
Abstract
Increasing food demand coupled with climate change pose a great challenge to agricultural systems. In this review we summarize recent advances in our knowledge of how plants, together with their associated microbiota, shape rhizosphere processes. We address (molecular) mechanisms operating at the plant-microbe-soil interface and aim to link this knowledge with actual and potential avenues for intensifying agricultural systems, while at the same time reducing irrigation water, fertilizer inputs and pesticide use. Combining in-depth knowledge about above and belowground plant traits will not only significantly advance our mechanistic understanding of involved processes but also allow for more informed decisions regarding agricultural practices and plant breeding. Including belowground plant-soil-microbe interactions in our breeding efforts will help to select crops resilient to abiotic and biotic environmental stresses and ultimately enable us to produce sufficient food in a more sustainable agriculture in the upcoming decades.
Collapse
Affiliation(s)
- Eva Oburger
- Department of Forest and Soil Science, Institute of Soil Research, University of Natural Resources and Life Sciences, Konrad Lorenzstrasse 24, 3430 Tulln an der Donau, Austria
| | - Hannes Schmidt
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Djerassiplatz 1, 1030 Vienna, Austria
| | - Christiana Staudinger
- Department of Forest and Soil Science, Institute of Soil Research, University of Natural Resources and Life Sciences, Konrad Lorenzstrasse 24, 3430 Tulln an der Donau, Austria
- Graduate School of Integrated Sciences for Life, Hiroshima University, Kagamiyama 1-7-1, Higashi-Hiroshima, Japan
| |
Collapse
|
2
|
Poucet T, González-Moro MB, Cabasson C, Beauvoit B, Gibon Y, Dieuaide-Noubhani M, Marino D. Ammonium supply induces differential metabolic adaptive responses in tomato according to leaf phenological stage. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:3185-3199. [PMID: 33578414 DOI: 10.1093/jxb/erab057] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 02/04/2021] [Indexed: 06/12/2023]
Abstract
Nitrate (NO3-) and ammonium (NH4+) are the main inorganic nitrogen sources available to plants. However, exclusive ammonium nutrition may lead to stress characterized by growth inhibition, generally associated with a profound metabolic reprogramming. In this work, we investigated how metabolism adapts according to leaf position in the vertical axis of tomato (Solanum lycopersicum cv. M82) plants grown with NH4+, NO3-, or NH4NO3 supply. We dissected leaf biomass composition and metabolism through an integrative analysis of metabolites, ions, and enzyme activities. Under ammonium nutrition, carbon and nitrogen metabolism were more perturbed in mature leaves than in young ones, overall suggesting a trade-off between NH4+ accumulation and assimilation to preserve young leaves from ammonium stress. Moreover, NH4+-fed plants exhibited changes in carbon partitioning, accumulating sugars and starch at the expense of organic acids, compared with plants supplied with NO3-. We explain such reallocation by the action of the biochemical pH-stat as a mechanism to compensate the differential proton production that depends on the nitrogen source provided. This work also underlines that the regulation of leaf primary metabolism is dependent on both leaf phenological stage and the nitrogen source provided.
Collapse
Affiliation(s)
- Théo Poucet
- Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo., Bilbao, Spain
- Université de Bordeaux, INRAE, UMR Biologie du Fruit et Pathologie, Villenave d'Ornon, France
| | - María Begoña González-Moro
- Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo., Bilbao, Spain
| | - Cécile Cabasson
- Université de Bordeaux, INRAE, UMR Biologie du Fruit et Pathologie, Villenave d'Ornon, France
| | - Bertrand Beauvoit
- Université de Bordeaux, INRAE, UMR Biologie du Fruit et Pathologie, Villenave d'Ornon, France
| | - Yves Gibon
- Université de Bordeaux, INRAE, UMR Biologie du Fruit et Pathologie, Villenave d'Ornon, France
| | | | - Daniel Marino
- Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo., Bilbao, Spain
- Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| |
Collapse
|
3
|
Feng H, Fan X, Miller AJ, Xu G. Plant nitrogen uptake and assimilation: regulation of cellular pH homeostasis. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:4380-4392. [PMID: 32206788 PMCID: PMC7382382 DOI: 10.1093/jxb/eraa150] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 03/19/2020] [Indexed: 05/10/2023]
Abstract
The enzymatic controlled metabolic processes in cells occur at their optimized pH ranges, therefore cellular pH homeostasis is fundamental for life. In plants, the nitrogen (N) source for uptake and assimilation, mainly in the forms of nitrate (NO3-) and ammonium (NH4+) quantitatively dominates the anion and cation equilibrium and the pH balance in cells. Here we review ionic and pH homeostasis in plant cells and regulation by N source from the rhizosphere to extra- and intracellular pH regulation for short- and long-distance N distribution and during N assimilation. In the process of N transport across membranes for uptake and compartmentation, both proton pumps and proton-coupled N transporters are essential, and their proton-binding sites may sense changes of apoplastic or intracellular pH. In addition, during N assimilation, carbon skeletons are required to synthesize amino acids, thus the combination of NO3- or NH4+ transport and assimilation results in different net charge and numbers of protons in plant cells. Efficient maintenance of N-controlled cellular pH homeostasis may improve N uptake and use efficiency, as well as enhance the resistance to abiotic stresses.
Collapse
Affiliation(s)
- Huimin Feng
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing, China
- MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, Nanjing, China
| | - Xiaorong Fan
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing, China
- MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, Nanjing, China
| | - Anthony J Miller
- Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich, UK
| | - Guohua Xu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing, China
- MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, Nanjing, China
| |
Collapse
|
4
|
Bulychev AA, Krupenina NA. Interchloroplast communications in Chara are suppressed under the alkaline bands and are relieved after the plasma membrane excitation. Bioelectrochemistry 2019; 129:62-69. [PMID: 31103848 DOI: 10.1016/j.bioelechem.2019.05.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 05/10/2019] [Accepted: 05/10/2019] [Indexed: 12/25/2022]
Abstract
Immobile chloroplasts in Chara internodal cells release photometabolites into the streaming cytoplasm that distributes the exported solutes and provides metabolic connectivity between spatially remote plastids. The metabolite transmission by fluid flow is evident from chlorophyll fluorescence changes in shaded chloroplasts upon local illumination applied upstream of the analyzed area. The connectivity correlates with the pH pattern on cell surface: it is strong in cell regions with high H+-pump activity and is low in regions featuring large passive H+ influx (OH- efflux). One explanation for low connectivity under the alkaline bands is that H+ influx lowers the cytoplasmic pH, thus retarding metabolic conversions of solutes carried by the microfluidic transporter. The cessation of H+ influx across the plasma membrane by eliciting the action potential and by adding NH4Cl into the medium greatly enhanced the amplitude of cyclosis-mediated fluorescence transients. The transition from latent to the transmissive state after the dark pretreatment was paralleled by the temporary increase in chlorophyll fluorescence, reflecting changes in photosynthetic electron transport. It is proposed that the connectivity between distant chloroplasts is controlled by cytoplasmic pH.
Collapse
Affiliation(s)
- Alexander A Bulychev
- Department of Biophysics, Faculty of Biology, Moscow State University, 119991 Moscow, Russia.
| | - Natalia A Krupenina
- Department of Biophysics, Faculty of Biology, Moscow State University, 119991 Moscow, Russia
| |
Collapse
|
5
|
Naher K, Miwa H, Okazaki S, Yasuda M. Effects of Different Sources of Nitrogen on Endophytic Colonization of Rice Plants by Azospirillum sp. B510. Microbes Environ 2018; 33:301-308. [PMID: 30158365 PMCID: PMC6167112 DOI: 10.1264/jsme2.me17186] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Azospirillum sp. B510, a free-living nitrogen-fixing bacterium isolated from the stems of rice (Oryza sativa cv. Nipponbare), was investigated to establish effective conditions for the colonization of rice plants. We analyzed the effects of the nitrogen sources KNO3, NH4Cl, urea (CO[NH2]2), and NH4NO3 at different concentrations (0.01–10 mM) on this colonization. Nitrogen promoted plant growth in a concentration-dependent manner, with minor differences being observed among the different nitrogen sources. Bacterial colonization was markedly suppressed on media containing NH4+ concentrations higher than 1 mM. Since concentrations of up to and including 10 mM NH4+ did not exhibit any antibacterial activity, we analyzed several factors affecting the NH4+-dependent inhibition of endophytic colonization, including the accumulation of the reactive oxygen species H2O2 and the secretion of the chemotactic substrate malic acid. The accumulation of H2O2 was increased in rice roots grown on 1 mM NH4Cl. The amounts of malic acid secreted from NH4-grown rice plants were lower than those secreted from plants grown without nitrogen or with KNO3. Although the bacterium exhibited chemotactic activity, moving towards root exudates from plants grown without nitrogen and KNO3-grown plants, this activity was not observed with root exudates from NH4+-grown plants. NH4+, but not NO3−, caused the acidification of growth media, which inhibited plant bacterial colonization. These NH4+-dependent phenomena were markedly suppressed by the stabilization of medium pH using a buffer. These results demonstrate that the type and concentration of nitrogen fertilizer affects the colonization of rice plants by Azospirillum sp. B510.
Collapse
Affiliation(s)
- Kamrun Naher
- Biological Production Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology
| | - Hiroki Miwa
- Biological Production Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology
| | - Shin Okazaki
- Biological Production Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology
| | - Michiko Yasuda
- Biological Production Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology
| |
Collapse
|
6
|
Beier MP, Obara M, Taniai A, Sawa Y, Ishizawa J, Yoshida H, Tomita N, Yamanaka T, Ishizuka Y, Kudo S, Yoshinari A, Takeuchi S, Kojima S, Yamaya T, Hayakawa T. Lack of ACTPK1, an STY kinase, enhances ammonium uptake and use, and promotes growth of rice seedlings under sufficient external ammonium. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 93:992-1006. [PMID: 29356222 DOI: 10.1111/tpj.13824] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 12/11/2017] [Accepted: 12/15/2017] [Indexed: 05/09/2023]
Abstract
Ammonium influx into plant roots via the high-affinity transport system (HATS) is down-modulated under elevated external ammonium, preventing ammonium toxicity. In ammonium-fed Arabidopsis, ammonium transporter 1 (AMT1) trimers responsible for HATS activity are allosterically inactivated in a dose-dependent manner via phosphorylation of the conserved threonine at the carboxyl-tail by the calcineurin B-like protein 1-calcineurin B-like protein-interacting protein kinase 23 complex and other yet unidentified protein kinases. Using transcriptome and reverse genetics in ammonium-preferring rice, we revealed the role of the serine/threonine/tyrosine protein kinase gene OsACTPK1 in down-modulation of HATS under sufficient ammonium. In wild-type roots, ACTPK1 mRNA and protein accumulated dose-dependently under sufficient ammonium. To determine the function of ACTPK1, two independent mutants lacking ACTPK1 were produced by retrotransposon Tos17 insertion. Compared with segregants lacking insertions, the two mutants showed decreased root growth and increased shoot growth under 1 mm ammonium due to enhanced ammonium acquisition, via aberrantly high HATS activity, and use. Furthermore, introduction of OsACTPK1 cDNA fused to the synthetic green fluorescence protein under its own promoter complemented growth and the HATS influx, and suggested plasma membrane localization. Root cellular expression of OsACTPK1 also overlapped with that of ammonium-induced OsAMT1;1 and OsAMT1;2. Meanwhile, threonine-phosphorylated AMT1 levels were substantially decreased in roots of ACTPK1-deficient mutants grown under sufficient ammonium. Bimolecular fluorescence complementation assay further confirmed interaction between ACTPK1 and AMT1;2 at the cell plasma membrane. Overall, these findings suggest that ACTPK1 directly phosphorylates and inactivates AMT1;2 in rice seedling roots under sufficient ammonium.
Collapse
Affiliation(s)
- Marcel P Beier
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Mitsuhiro Obara
- Japan International Research Center for Agricultural Sciences, 1-1 Ohwashi, Tsukuba, Ibaraki, 305-8686, Japan
| | - Akiko Taniai
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Yuki Sawa
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Jin Ishizawa
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Haruki Yoshida
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Narumi Tomita
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Tsuyoshi Yamanaka
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Yawara Ishizuka
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Syuko Kudo
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Akira Yoshinari
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Shiho Takeuchi
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Soichi Kojima
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Tomoyuki Yamaya
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Toshihiko Hayakawa
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| |
Collapse
|
7
|
Baxi K, Ghavidel A, Waddell B, Harkness TA, de Carvalho CE. Regulation of Lysosomal Function by the DAF-16 Forkhead Transcription Factor Couples Reproduction to Aging in Caenorhabditis elegans. Genetics 2017; 207:83-101. [PMID: 28696216 PMCID: PMC5586388 DOI: 10.1534/genetics.117.204222] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 07/03/2017] [Indexed: 02/06/2023] Open
Abstract
Aging in eukaryotes is accompanied by widespread deterioration of the somatic tissue. Yet, abolishing germ cells delays the age-dependent somatic decline in Caenorhabditis elegans In adult worms lacking germ cells, the activation of the DAF-9/DAF-12 steroid signaling pathway in the gonad recruits DAF-16 activity in the intestine to promote longevity-associated phenotypes. However, the impact of this pathway on the fitness of normally reproducing animals is less clear. Here, we explore the link between progeny production and somatic aging and identify the loss of lysosomal acidity-a critical regulator of the proteolytic output of these organelles-as a novel biomarker of aging in C. elegans The increase in lysosomal pH in older worms is not a passive consequence of aging, but instead is timed with the cessation of reproduction, and correlates with the reduction in proteostasis in early adult life. Our results further implicate the steroid signaling pathway and DAF-16 in dynamically regulating lysosomal pH in the intestine of wild-type worms in response to the reproductive cycle. In the intestine of reproducing worms, DAF-16 promotes acidic lysosomes by upregulating the expression of v-ATPase genes. These findings support a model in which protein clearance in the soma is linked to reproduction in the gonad via the active regulation of lysosomal acidification.
Collapse
Affiliation(s)
- Kunal Baxi
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan S7N5E2, Canada
| | - Ata Ghavidel
- Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, Saskatchewan S7N5E2, Canada
| | - Brandon Waddell
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan S7N5E2, Canada
| | - Troy A Harkness
- Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, Saskatchewan S7N5E2, Canada
| | - Carlos E de Carvalho
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan S7N5E2, Canada
| |
Collapse
|
8
|
Liu Y, von Wirén N. Ammonium as a signal for physiological and morphological responses in plants. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:2581-2592. [PMID: 28369490 DOI: 10.1093/jxb/erx086] [Citation(s) in RCA: 177] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Ammonium is a major inorganic nitrogen source for plants. At low external supplies, ammonium promotes plant growth, while at high external supplies it causes toxicity. Ammonium triggers rapid changes in cytosolic pH, in gene expression, and in post-translational modifications of proteins, leading to apoplastic acidification, co-ordinated ammonium uptake, enhanced ammonium assimilation, altered oxidative and phytohormonal status, and reshaped root system architecture. Some of these responses are dependent on AMT-type ammonium transporters and are not linked to a nutritional effect, indicating that ammonium is perceived as a signaling molecule by plant cells. This review summarizes current knowledge of ammonium-triggered physiological and morphological responses and highlights existing and putative mechanisms mediating ammonium signaling and sensing events in plants. We put forward the hypothesis that sensing of ammonium takes place at multiple steps along its transport, storage, and assimilation pathways.
Collapse
Affiliation(s)
- Ying Liu
- Molecular Plant Nutrition, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Stadt Seeland, OT Gatersleben, Germany
| | - Nicolaus von Wirén
- Molecular Plant Nutrition, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Stadt Seeland, OT Gatersleben, Germany
| |
Collapse
|
9
|
Overexpression of a pH-sensitive nitrate transporter in rice increases crop yields. Proc Natl Acad Sci U S A 2016; 113:7118-23. [PMID: 27274069 DOI: 10.1073/pnas.1525184113] [Citation(s) in RCA: 190] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Cellular pH homeostasis is fundamental for life, and all cells adapt to maintain this balance. In plants, the chemical form of nitrogen supply, nitrate and ammonium, is one of the cellular pH dominators. We report that the rice nitrate transporter OsNRT2.3 is transcribed into two spliced isoforms with a natural variation in expression ratio. One splice form, OsNRT2.3b is located on the plasma membrane, is expressed mainly in the phloem, and has a regulatory motif on the cytosolic side that acts to switch nitrate transport activity on or off by a pH-sensing mechanism. High OsNRT2.3b expression in rice enhances the pH-buffering capacity of the plant, increasing N, Fe, and P uptake. In field trials, increased expression of OsNRT2.3b improved grain yield and nitrogen use efficiency (NUE) by 40%. These results indicate that pH sensing by the rice nitrate transporter OsNRT2.3b is important for plant adaption to varied N supply forms and can provide a target for improving NUE.
Collapse
|
10
|
Coskun D, Britto DT, Li M, Becker A, Kronzucker HJ. Rapid ammonia gas transport accounts for futile transmembrane cycling under NH3/NH4+ toxicity in plant roots. PLANT PHYSIOLOGY 2013; 163:1859-67. [PMID: 24134887 PMCID: PMC3850193 DOI: 10.1104/pp.113.225961] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 10/14/2013] [Indexed: 05/17/2023]
Abstract
Futile transmembrane NH3/NH4(+) cycling in plant root cells, characterized by extremely rapid fluxes and high efflux to influx ratios, has been successfully linked to NH3/NH4(+) toxicity. Surprisingly, the fundamental question of which species of the conjugate pair (NH3 or NH4(+)) participates in such fluxes is unresolved. Using flux analyses with the short-lived radioisotope (13)N and electrophysiological, respiratory, and histochemical measurements, we show that futile cycling in roots of barley (Hordeum vulgare) seedlings is predominately of the gaseous NH3 species, rather than the NH4(+) ion. Influx of (13)NH3/(13)NH4(+), which exceeded 200 µmol g(-1) h(-1), was not commensurate with membrane depolarization or increases in root respiration, suggesting electroneutral NH3 transport. Influx followed Michaelis-Menten kinetics for NH3 (but not NH4(+)), as a function of external concentration (Km = 152 µm, Vmax = 205 µmol g(-1) h(-1)). Efflux of (13)NH3/(13)NH4(+) responded with a nearly identical Km. Pharmacological characterization of influx and efflux suggests mediation by aquaporins. Our study fundamentally revises the futile-cycling model by demonstrating that NH3 is the major permeating species across both plasmalemma and tonoplast of root cells under toxicity conditions.
Collapse
Affiliation(s)
- Devrim Coskun
- Department of Biological Sciences, University of Toronto, 1265 Military Trail, Toronto, Ontario, Canada M1C 1A4
| | - Dev T. Britto
- Department of Biological Sciences, University of Toronto, 1265 Military Trail, Toronto, Ontario, Canada M1C 1A4
| | - Mingyuan Li
- Department of Biological Sciences, University of Toronto, 1265 Military Trail, Toronto, Ontario, Canada M1C 1A4
| | - Alexander Becker
- Department of Biological Sciences, University of Toronto, 1265 Military Trail, Toronto, Ontario, Canada M1C 1A4
| | - Herbert J. Kronzucker
- Department of Biological Sciences, University of Toronto, 1265 Military Trail, Toronto, Ontario, Canada M1C 1A4
| |
Collapse
|
11
|
Weise T, Kai M, Piechulla B. Bacterial ammonia causes significant plant growth inhibition. PLoS One 2013; 8:e63538. [PMID: 23691060 PMCID: PMC3655192 DOI: 10.1371/journal.pone.0063538] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 04/02/2013] [Indexed: 11/19/2022] Open
Abstract
Many and complex plant-bacteria inter-relationships are found in the rhizosphere, since plants release a variety of photosynthetic exudates from their roots and rhizobacteria produce multifaceted specialized compounds including rich mixtures of volatiles, e.g., the bouquet of Serratia odorifera 4Rx13 is composed of up to 100 volatile organic and inorganic compounds. Here we show that when growing on peptone-rich nutrient medium S. odorifera 4Rx13 and six other rhizobacteria emit high levels of ammonia, which during co-cultivation in compartmented Petri dishes caused alkalization of the neighboring plant medium and subsequently reduced the growth of A. thaliana. It is argued that in nature high-protein resource degradations (carcasses, whey, manure and compost) are also accompanied by bacterial ammonia emission which alters the pH of the rhizosphere and thereby influences organismal diversity and plant-microbe interactions. Consequently, bacterial ammonia emission may be more relevant for plant colonization and growth development than previously thought.
Collapse
Affiliation(s)
- Teresa Weise
- University of Rostock, Institute of Biological Sciences, Rostock, Germany
| | - Marco Kai
- University of Rostock, Institute of Biological Sciences, Rostock, Germany
| | - Birgit Piechulla
- University of Rostock, Institute of Biological Sciences, Rostock, Germany
- * E-mail:
| |
Collapse
|
12
|
Hachiya T, Watanabe CK, Fujimoto M, Ishikawa T, Takahara K, Kawai-Yamada M, Uchimiya H, Uesono Y, Terashima I, Noguchi K. Nitrate Addition Alleviates Ammonium Toxicity Without Lessening Ammonium Accumulation, Organic Acid Depletion and Inorganic Cation Depletion in Arabidopsis thaliana Shoots. ACTA ACUST UNITED AC 2012; 53:577-91. [DOI: 10.1093/pcp/pcs012] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
|
13
|
Wieneke J, Roeb GW. Effect of methionine sulphoximine on13 N-ammonium fluxes in the roots of barley and squash seedlings. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/jpln.1998.3581610102] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
14
|
Ariz I, Cruz C, Moran JF, González-Moro MB, García-Olaverri C, González-Murua C, Martins-Loução MA, Aparicio-Tejo PM. Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants. BMC PLANT BIOLOGY 2011; 11:83. [PMID: 21575190 PMCID: PMC3224212 DOI: 10.1186/1471-2229-11-83] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 05/16/2011] [Indexed: 05/23/2023]
Abstract
BACKGROUND In plants, nitrate (NO3-) nutrition gives rise to a natural N isotopic signature (δ15N), which correlates with the δ15N of the N source. However, little is known about the relationship between the δ15N of the N source and the 14N/15N fractionation in plants under ammonium (NH4+) nutrition. When NH4+ is the major N source, the two forms, NH4+ and NH3, are present in the nutrient solution. There is a 1.025 thermodynamic isotope effect between NH3 (g) and NH4+ (aq) which drives to a different δ15N. Nine plant species with different NH4+-sensitivities were cultured hydroponically with NO3- or NH4+ as the sole N sources, and plant growth and δ15N were determined. Short-term NH4+/NH3 uptake experiments at pH 6.0 and 9.0 (which favours NH3 form) were carried out in order to support and substantiate our hypothesis. N source fractionation throughout the whole plant was interpreted on the basis of the relative transport of NH4+ and NH3. RESULTS Several NO3--fed plants were consistently enriched in 15N, whereas plants under NH4+ nutrition were depleted of 15N. It was shown that more sensitive plants to NH4+ toxicity were the most depleted in 15N. In parallel, N-deficient pea and spinach plants fed with 15NH4+ showed an increased level of NH3 uptake at alkaline pH that was related to the 15N depletion of the plant. Tolerant to NH4+ pea plants or sensitive spinach plants showed similar trend on 15N depletion while slight differences in the time kinetics were observed during the initial stages. The use of RbNO3 as control discarded that the differences observed arise from pH detrimental effects. CONCLUSIONS This article proposes that the negative values of δ15N in NH4+-fed plants are originated from NH3 uptake by plants. Moreover, this depletion of the heavier N isotope is proportional to the NH4+/NH3 toxicity in plants species. Therefore, we hypothesise that the low affinity transport system for NH4+ may have two components: one that transports N in the molecular form and is associated with fractionation and another that transports N in the ionic form and is not associated with fractionation.
Collapse
Affiliation(s)
- Idoia Ariz
- Instituto de Agrobiotecnología, IdAB – CSIC - Universidad Pública de Navarra - Gobierno de Navarra, Campus de Arrosadía s/n, E-31006 Pamplona, Navarra, Spain
| | - Cristina Cruz
- Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental - CBA, Campo Grande, Bloco C-4, Piso 1, 1749-016 Lisboa, Portugal
| | - Jose F Moran
- Instituto de Agrobiotecnología, IdAB – CSIC - Universidad Pública de Navarra - Gobierno de Navarra, Campus de Arrosadía s/n, E-31006 Pamplona, Navarra, Spain
| | - María B González-Moro
- Department of Plant Biology and Ecology, Faculty of Science and Technology, University of Basque Country (UPV-EHU), Apdo. 644; E-48080 Bilbao, Vizcaya, Spain
| | - Carmen García-Olaverri
- Department of Statistics and Operations Research, Public University of Navarre, Campus de Arrosadía s/n, E-31006 Pamplona, Navarra, Spain
| | - Carmen González-Murua
- Department of Plant Biology and Ecology, Faculty of Science and Technology, University of Basque Country (UPV-EHU), Apdo. 644; E-48080 Bilbao, Vizcaya, Spain
| | - Maria A Martins-Loução
- Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental - CBA, Campo Grande, Bloco C-4, Piso 1, 1749-016 Lisboa, Portugal
| | - Pedro M Aparicio-Tejo
- Instituto de Agrobiotecnología, IdAB – CSIC - Universidad Pública de Navarra - Gobierno de Navarra, Campus de Arrosadía s/n, E-31006 Pamplona, Navarra, Spain
| |
Collapse
|
15
|
Hachiya T, Watanabe CK, Boom C, Tholen D, Takahara K, Kawai-Yamada M, Uchimiya H, Uesono Y, Terashima I, Noguchi K. Ammonium-dependent respiratory increase is dependent on the cytochrome pathway in Arabidopsis thaliana shoots. PLANT, CELL & ENVIRONMENT 2010; 33:1888-97. [PMID: 20545883 DOI: 10.1111/j.1365-3040.2010.02189.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Oxygen uptake rates are increased when concentrated ammonium instead of nitrate is used as sole N source. Several explanations for this increased respiration have been suggested, but the underlying mechanisms are still unclear. To investigate possible factors responsible for this respiratory increase, we measured the O₂ uptake rate, activity and transcript level of respiratory components, and concentration of adenylates using Arabidopsis thaliana shoots grown in media containing various N sources. The O₂ uptake rate was correlated with concentrations of ammonium and ATP in shoots, but not related to the ammonium assimilation. The capacity of the ATP-coupling cytochrome pathway (CP) and its related genes were up-regulated when concentrated ammonium was sole N source, whereas the ATP-uncoupling alternative oxidase did not influence the extent of the respiratory increase. Our results suggest that the ammonium-dependent increase of the O₂ uptake rate can be explained by the up-regulation of the CP, which may be related to the ATP consumption by the plasma-membrane H+ -ATPase.
Collapse
Affiliation(s)
- Takushi Hachiya
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
YANG J, LU CY. Possible Mechanism Associated with Herbicidal Activity of Soybean Meal Hydrolysate (SMH). ACTA ACUST UNITED AC 2010. [DOI: 10.1016/s1671-2927(09)60164-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
17
|
Ruan J, Gerendás J, Härdter R, Sattelmacher B. Effect of nitrogen form and root-zone pH on growth and nitrogen uptake of tea (Camellia sinensis) plants. ANNALS OF BOTANY 2007; 99:301-10. [PMID: 17204540 PMCID: PMC2802997 DOI: 10.1093/aob/mcl258] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
BACKGROUND AND AIMS Tea (Camellia sinensis) is considered to be acid tolerant and prefers ammonium nutrition, but the interaction between root zone acidity and N form is not properly understood. The present study was performed to characterize their interaction with respect to growth and mineral nutrition. METHODS Tea plants were hydroponically cultured with NH4+, NO3- and NH(4+) + NO3-, at pH 4.0, 5.0 and 6.0, which were maintained by pH stat systems. KEY RESULTS Plants supplied with NO3- showed yellowish leaves resembling nitrogen deficiency and grew much slower than those receiving NH4+ or NH(4+) + NO3- irrespective of root-zone pH. Absorption of NH4+ was 2- to 3.4-fold faster than NO3- when supplied separately, and 6- to 16-fold faster when supplied simultaneously. Nitrate-grown plants had significantly reduced glutamine synthetase activity, and lower concentrations of total N, free amino acids and glucose in the roots, but higher concentrations of cations and carboxylates (mainly oxalate) than those grown with NH4+ or NH(4+) + NO3-. Biomass production was largest at pH 5.0 regardless of N form, and was drastically reduced by a combination of high root-zone pH and NO3-. Low root-zone pH reduced root growth only in NO(3-)-fed plants. Absorption of N followed a similar pattern as root-zone pH changed, showing highest uptake rates at pH 5.0. The concentrations of total N, free amino acids, sugars and the activity of GS were generally not influenced by pH, whereas the concentrations of cations and carboxylates were generally increased with increasing root-zone pH. CONCLUSIONS Tea plants are well-adapted to NH(4+)-rich environments by exhibiting a high capacity for NH4+ assimilation in their roots, reflected in strongly increased key enzyme activities and improved carbohydrate status. The poor plant growth with NO3- was largely associated with inefficient absorption of this N source. Decreased growth caused by inappropriate external pH corresponded well with the declining absorption of nitrogen.
Collapse
Affiliation(s)
- Jianyun Ruan
- Institute for Plant Nutrition and Soil Science, Kiel University, Kiel, D-24098, Germany.
| | | | | | | |
Collapse
|
18
|
Prusky D, Lichter A. Activation of quiescent infections by postharvest pathogens during transition from the biotrophic to the necrotrophic stage. FEMS Microbiol Lett 2007; 268:1-8. [PMID: 17227463 DOI: 10.1111/j.1574-6968.2006.00603.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Insidious fungal infections of postharvest pathogens remain quiescent, as biotrophs, during fruit growth and harvest, but activate their development and transform to necrotrophs, which elicit decay symptoms, during ripening and senescence. Exposure of unripe hosts to pathogens quickly initiates defensive signal-transduction cascades that limit fungal growth and development, but exposure to the same pathogens during ripening and storage activates a substantially different signaling cascade that facilitates fungal colonization. The first step in the activation of quiescent infections may involve the fungal capability to cope with plant defense responses by detoxification and efflux transport of antifungals, or by overcoming the suppression of pathogenicity factors. The second step toward the activation of quiescent infections is actively modulated by the pathogen in response to a host signal(s), and includes alkalization or ammonification of the host tissue, which sensitizes the host and activates the transcription and secretion of fungal-degradative enzymes that promote maceration of the host tissue. Feedback signals involving, for example, nitrogen and sugar further enhance pH changes, synthesis of hydrolytic enzymes and saprophytic development in the macerated tissue. This review describes the coordinated series of mechanisms that regulate the activation of quiescent infections in various fruit/vegetable-pathogen interactions.
Collapse
Affiliation(s)
- Dov Prusky
- Department of Postharvest Science of Fresh Produce, Agricultural Research Organization, Bet Dagan, Israel.
| | | |
Collapse
|
19
|
Britto DT, Kronzucker HJ. NH4+ toxicity in higher plants: a critical review. JOURNAL OF PLANT PHYSIOLOGY 2002. [PMID: 0 DOI: 10.1078/0176-1617-0774] [Citation(s) in RCA: 671] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
|
20
|
Walker RP, Chen ZH, Johnson KE, Famiani F, Tecsi L, Leegood RC. Using immunohistochemistry to study plant metabolism: the examples of its use in the localization of amino acids in plant tissues, and of phosphoenolpyruvate carboxykinase and its possible role in pH regulation. JOURNAL OF EXPERIMENTAL BOTANY 2001; 52:565-576. [PMID: 11373305 DOI: 10.1093/jexbot/52.356.565] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
To understand many aspects of the metabolism of complex plant structures such as leaves, fruit and roots it is important to understand how metabolic processes are compartmentalized between tissues. The aim of this article is to show how immunohistochemistry, in conjunction with biochemical and physiological studies, is useful in understanding both the function of an enzyme in a tissue and metabolic processes occurring in plant tissues. This is illustrated by two examples. Firstly, the use of immunohistochemisty in the localization of amino acids in plant tissues is described. Secondly, the use of immunohistochemistry in understanding the function of an enzyme in a tissue and the metabolic processes occurring within the tissue is described. To illustrate this the example of phosophoenolpyruvate carboxykinase (PEPCK), an enzyme which is present in many plant tissues in which its function is unknown, is used. Evidence is provided that PEPCK may play a role in pH regulation in tissues active in the metabolism of nitrogen.
Collapse
Affiliation(s)
- R P Walker
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK. Istituto di Coltivazioni Arboree, Universita degli Studi di Perugia, via BorgoXX Guigno, 74-06121 Perugia, Italy.
| | | | | | | | | | | |
Collapse
|
21
|
Britto DT, Glass AD, Kronzucker HJ, Siddiqi MY. Cytosolic concentrations and transmembrane fluxes of NH4+/NH3. An evaluation of recent proposals. PLANT PHYSIOLOGY 2001; 125:523-6. [PMID: 11161009 PMCID: PMC1539362 DOI: 10.1104/pp.125.2.523] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Affiliation(s)
- D T Britto
- Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4
| | | | | | | |
Collapse
|
22
|
Gerendás J, Ratcliffe RG. Intracellular pH regulation in maize root tips exposed to ammonium at high external pH. JOURNAL OF EXPERIMENTAL BOTANY 2000; 51:207-219. [PMID: 10938827 DOI: 10.1093/jexbot/51.343.207] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Ammonium-induced changes in the cytoplasmic and vacuolar pH values of excised maize (Zea mays L.) root tips, measured by in vivo 31P nuclear magnetic resonance (NMR) spectroscopy, were correlated with the ammonium content of the tissue, determined by 14N NMR. Calculations based on these measurements indicated that the pH changes observed during exposure to 10 mM ammonium for 1 h at pH 9.0, and in the recovery following the removal of the external ammonium supply, were largely determined by the influx and efflux of the weak base NH3. Carboxylate synthesis, detected by both in vivo 13C NMR and the incorporation of [14C]bicarbonate, was stimulated by the ammonium-induced alkalinization of the root tips, but the contribution that this proton-generating process made to pH regulation during and after the ammonium treatment was quantitatively insignificant. Similarly, ammonium assimilation, which was shown to occur via the proton-generating glutamine synthetase/glutamate synthase pathway using in vivo 15N NMR, was also quantitatively insignificant in comparison with the large changes in ammonium content that occurred during the ammonium treatment and subsequent recovery. The results are discussed in relation to several recent studies in which ammonium was used to perturb intracellular pH values, and it is argued (i) that a new method for probing the subcellular compartmentation of amino acids, based on an ammonium-induced alkalinization of the cytoplasm may be difficult to implement in dense heterogeneous tissues; and (ii) that observations on the apparently proton-consuming effect of ammonium assimilation in rice root hairs may actually reflect unusually rapid assimilation.
Collapse
Affiliation(s)
- J Gerendás
- Institute for Plant Nutrition and Soil Science, University of Kiel, Germany.
| | | |
Collapse
|
23
|
Gilroy S, Jones DL. Through form to function: root hair development and nutrient uptake. TRENDS IN PLANT SCIENCE 2000; 5:56-60. [PMID: 10664614 DOI: 10.1016/s1360-1385(99)01551-4] [Citation(s) in RCA: 224] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Root hairs project from the surface of the root to aid nutrient and water uptake and to anchor the plant in the soil. Their formation involves the precise control of cell fate and localized cell growth. We are now beginning to unravel the complexities of the molecular interactions that underlie this developmental regulation. In addition, after years of speculation, nutrient transport by root hairs has been demonstrated clearly at the physiological and molecular level, with evidence for root hairs being intense sites of H(+)-ATPase activity and involved in the uptake of Ca(2+), K(+), NH(4)(+), NO(3)(-), Mn(2+), Zn(2+), Cl(-) and H(2)PO(4)(-).
Collapse
Affiliation(s)
- S Gilroy
- Biology Dept, The Pennsylvania State University, 208 Mueller Laboratory, University Park, PA 16802, USA.
| | | |
Collapse
|
24
|
Takano M, Shimmen T. Effects of aluminum on plasma membrane as revealed by analysis of alkaline band formation in internodal cells of Chara corallina. Cell Struct Funct 1999; 24:131-7. [PMID: 10462175 DOI: 10.1247/csf.24.131] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
To study the mechanism of aluminum toxicity in plant cells, the effects of aluminum on alkaline band formation were analyzed in the internodal cells of Chara. After cells were treated with AlCl3, they were examined for their capacity to develop alkaline bands. Treating cells with AlCl3 medium at pH 4.5 completely inhibited alkaline band formation. When either CaCl2 or malic acid was added to the AlCl3 medium (pH 4.5), it did not produce an ameliorative effect, whereas addition of both CaCl2 and malic acid induced a significant ameliorative effect. It was found that treatment at pH 4.5 in the absence of AlCl3 strongly inhibited alkaline band formation. This inhibition by the low pH (4.5) treatment was effectively ameliorated by CaCl2. At higher pH (5.0), malic acid alone produced a significant ameliorative effect on aluminum inhibition of alkaline band formation, but CaCl2 did not. Recovery from aluminum inhibition was also studied. When cells treated with AlCl3 at pH 4.5 were incubated in artificial pond water, they could not recover the capacity to develop alkaline band. When either malic acid or CaCl2 was added to artificial pond water, cells recovered their alkaline band formation. It was concluded that one of the primary targets of aluminum is the plasma membrane and that aluminum affects the plasma membrane from the cell exterior at the beginning of the treatment (within 24 h). It was also suggested that the aluminum treatment impairs the HCO3- influx mechanism but not the OH- efflux mechanism.
Collapse
Affiliation(s)
- M Takano
- Department of Life Sciences, Faculty of Science, Himeji Institute of Technology, Harima Science Park City, Hyogo, Japan
| | | |
Collapse
|
25
|
Bibikova TN, Jacob T, Dahse I, Gilroy S. Localized changes in apoplastic and cytoplasmic pH are associated with root hair development in Arabidopsis thaliana. Development 1998; 125:2925-34. [PMID: 9655814 DOI: 10.1242/dev.125.15.2925] [Citation(s) in RCA: 128] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Morphogenesis in plants is characterized by highly regulated cell enlargement. However, the mechanisms controlling and localizing regions of growth remain essentially unknown. Root hair formation involves the induction of a localized cell expansion in the lateral wall of a root epidermal cell. This expanded region then enters a second phase of localized growth called tip growth. Root hair formation therefore provides a model in which to study the cellular events involved in regulating localized growth in plants. Confocal ratio imaging of the pH of the cell wall revealed an acidification at the root hair initiation site. This acidification was present from the first morphological indications of localized growth, but not before, and was maintained to the point where the process of root hair initiation ceased and tip growth began. Preventing the wall acidification with pH buffers arrested the initiation process but growth resumed when the wall was returned to an acidic pH. Cytoplasmic pH was found to be elevated from approximately 7.3 to 7. 7 at the initiation site, and this elevation coincided with the acidification of the wall. Preventing the localized increase in cytoplasmic pH with 10 mM butyrate however did not inhibit either the wall acidification or the initiation process. In contrast, there was no detectable gradient in pH associated with the apex of tip growing root hairs, but both elevated apoplastic pH and butyrate treatment irreversibly inhibited the tip growth process. Thus the processes of tip growth and initiation of root hairs show differences in their pH requirements. These results highlight the role of localized control of apoplastic pH in the control of cell architecture and morphogenesis in plants.
Collapse
Affiliation(s)
- T N Bibikova
- Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA.
| | | | | | | |
Collapse
|