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Hosoda E, Chiba K. Fluorescence Measurement and Calibration of Intracellular pH in Starfish Oocytes. Bio Protoc 2020; 10:e3778. [PMID: 33659434 DOI: 10.21769/bioprotoc.3778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 07/27/2020] [Accepted: 08/17/2020] [Indexed: 11/02/2022] Open
Abstract
Oocyte maturation is a process wherein an oocyte arrested at prophase of meiosis I resumes meiosis to become a fertilizable egg. In starfish ovaries, a hormone released from follicle cells activates the oocytes, resulting in an increase in their intracellular pH (pHi), which is required for spindle assembly. Herein, we describe a protocol for pHi measurement in living oocytes microinjected with the pH-sensitive dye BCECF. For in vivo BCECF calibration, we treated oocytes with artificial seawater containing CH3COONH4 to clamp pHi, injected pH-standard solutions, and converted the BCECF fluorescence intensity ratios to pHi values. Of note, if the actual pHi is higher or lower than the known pH of injected standard solutions, the BCECF fluorescence intensity ratio will decrease or increase, respectively. On the other hand, the pH of the injected solution displaying no change in fluorescence intensity should be considered the actual pHi. These methods for pHi calibration and clamping are simple and reproducible.
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Affiliation(s)
- Enako Hosoda
- Department of Biological Sciences, Ochanomizu University, Tokyo, Japan
| | - Kazuyoshi Chiba
- Department of Biological Sciences, Ochanomizu University, Tokyo, Japan
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Rajagopal D, Mathew MK. Role of Arabidopsis RAB5 GEF vps9a in maintaining potassium levels under sodium chloride stress. PLANT DIRECT 2020; 4:e00273. [PMID: 33103044 PMCID: PMC7576885 DOI: 10.1002/pld3.273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 09/06/2020] [Accepted: 09/10/2020] [Indexed: 05/07/2023]
Abstract
Salt stress is one of the major factors impacting crop productivity worldwide. Through a variety of effector and signaling pathways, plants achieve survival under salinity stress by maintaining high cytosolic potassium/sodium ion (K+/Na+) ratios, preventing Na+ cytotoxicity, and retaining osmotic balance. Ras-related protein 5 (Rab5) members are involved in the trafficking of endosomes to the vacuole or plasma membrane (PM). The vacuolar protein sorting- associated protein 9 (vps9a) encodes the single guanine nucleotide exchange factor (GEF) that activates all three known Rab5 proteins in Arabidopsis thaliana. Previous work from our group has reported the critical function of vps9a for the operation of salt-induced endocytic pathway, as well as the expansion of endomembrane compartments under saline stress conditions. Here we show an additional role of vps9a in plant response to salt stress via maintenance of K+ status of the cell rather than Na+ homeostasis. Our results show that roots from vps9a-2 mutant, subjected to 100 mM NaCl, display alterations in transcript levels of genes involved in the K+ homeostasis pathway. Concurrent with the observed sensitivity of vps9a-2 mutant under NaCl stress, exposure to low K+ environments resulted in growth retardation, and reduced rate of endocytosis. Furthermore, vps9a-2 mutant displays reduced expression of auxin reporter, Direct Repeat-5 (DR5), and alterations in polarity and abundance of auxin efflux carrier PIN- FORMED2 (PIN2). Imposition of NaCl stress was found to be restrictive to the elongation capacity of cells in the root elongation zone of vps9a-2 mutant. Together our results indicate that alterations in K+ homeostasis and associated cellular changes causing increased cell wall pH, contribute to diminished root growth and compromised survival of vps9a-2 mutant under salt stress conditions.
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Affiliation(s)
- Divya Rajagopal
- National Centre for Biological SciencesTIFRBangaloreKarnatakaIndia
| | - M. K. Mathew
- National Centre for Biological SciencesTIFRBangaloreKarnatakaIndia
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Basu D, Haswell ES. The Mechanosensitive Ion Channel MSL10 Potentiates Responses to Cell Swelling in Arabidopsis Seedlings. Curr Biol 2020; 30:2716-2728.e6. [PMID: 32531281 DOI: 10.1016/j.cub.2020.05.015] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 05/01/2020] [Accepted: 05/05/2020] [Indexed: 01/06/2023]
Abstract
The ability to respond to unanticipated increases in volume is a fundamental property of cells, essential for cellular integrity in the face of osmotic challenges. Plants must manage cell swelling during flooding, rehydration, and pathogen invasion-but little is known about the mechanisms by which this occurs. It has been proposed that plant cells could sense and respond to cell swelling through the action of mechanosensitive ion channels. Here, we characterize a new assay to study the effects of cell swelling on Arabidopsis thaliana seedlings and to test the contributions of the mechanosensitive ion channel MscS-like10 (MSL10). The assay incorporates both cell wall softening and hypo-osmotic treatment to induce cell swelling. We show that MSL10 is required for several previously demonstrated responses to hypo-osmotic shock, including a cytoplasmic calcium transient within the first few seconds, accumulation of ROS within the first 30 min, and increased transcript levels of mechano-inducible genes within 60 min. We also show that cell swelling induces programmed cell death within 3 h in a MSL10-dependent manner. Finally, we show that MSL10 is unable to potentiate cell swelling-induced death when phosphomimetic residues are introduced into its soluble N terminus. Thus, MSL10 functions as a phospho-regulated membrane-based sensor that connects the perception of cell swelling to a downstream signaling cascade and programmed cell death.
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Affiliation(s)
- Debarati Basu
- NSF Center for Engineering Mechanobiology, Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Elizabeth S Haswell
- NSF Center for Engineering Mechanobiology, Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA.
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Sade N, Del Mar Rubio Wilhelmi M, Ke X, Brotman Y, Wright M, Khan I, De Souza W, Bassil E, Tobias CM, Thilmony R, Vogel JP, Blumwald E. Salt tolerance of two perennial grass Brachypodium sylvaticum accessions. PLANT MOLECULAR BIOLOGY 2018; 96:305-314. [PMID: 29322303 DOI: 10.1007/s11103-017-0696-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 12/27/2017] [Indexed: 06/07/2023]
Abstract
We studied the salt stress tolerance of two accessions isolated from different areas of the world (Norway and Tunisia) and characterized the mechanism(s) regulating salt stress in Brachypodium sylvaticum Osl1 and Ain1. Perennial grasses are widely grown in different parts of the world as an important feedstock for renewable energy. Their perennial nature that reduces management practices and use of energy and agrochemicals give these biomass crops advantages when dealing with modern agriculture challenges such as soil erosion, increase in salinized marginal lands and the runoff of nutrients. Brachypodium sylvaticum is a perennial grass that was recently suggested as a suitable model for the study of biomass plant production and renewable energy. However, its plasticity to abiotic stress is not yet clear. We studied the salt stress tolerance of two accessions isolated from different areas of the world and characterized the mechanism(s) regulating salt stress in B. sylvaticum Osl1, originated from Oslo, Norway and Ain1, originated from Ain-Durham, Tunisia. Osl1 limited sodium transport from root to shoot, maintaining a better K/Na homeostasis and preventing toxicity damage in the shoot. This was accompanied by higher expression of HKT8 and SOS1 transporters in Osl1 as compared to Ain1. In addition, Osl1 salt tolerance was accompanied by higher abundance of the vacuolar proton pump pyrophosphatase and Na+/H+ antiporters (NHXs) leading to a better vacuolar pH homeostasis, efficient compartmentation of Na+ in the root vacuoles and salt tolerance. Although preliminary, our results further support previous results highlighting the role of Na+ transport systems in plant salt tolerance. The identification of salt tolerant and sensitive B. sylvaticum accessions can provide an experimental system for the study of the mechanisms and regulatory networks associated with stress tolerance in perennials grass.
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Affiliation(s)
- Nir Sade
- Department of Plant Sciences, University of California, 1 Shields Ave, Mail Stop 5, Davis, CA, 95616, USA
| | | | - Xiaojuan Ke
- Department of Plant Sciences, University of California, 1 Shields Ave, Mail Stop 5, Davis, CA, 95616, USA
| | - Yariv Brotman
- Department of Life Sciences, Ben Gurion University of the Negev, Beersheva, Israel
| | - Matthew Wright
- Department of Plant Sciences, University of California, 1 Shields Ave, Mail Stop 5, Davis, CA, 95616, USA
| | - Imran Khan
- Department of Plant Sciences, University of California, 1 Shields Ave, Mail Stop 5, Davis, CA, 95616, USA
- Department of Agronomy, University of Agriculture, Faisalabad, Pakistan
| | - Wagner De Souza
- Department of Plant Sciences, University of California, 1 Shields Ave, Mail Stop 5, Davis, CA, 95616, USA
| | - Elias Bassil
- Department of Plant Sciences, University of California, 1 Shields Ave, Mail Stop 5, Davis, CA, 95616, USA
| | - Christian M Tobias
- Western Regional Research Center, United States Department of Agriculture, Agricultural Research Service, Albany, CA, USA
| | - Roger Thilmony
- Western Regional Research Center, United States Department of Agriculture, Agricultural Research Service, Albany, CA, USA
| | - John P Vogel
- DOE Joint Genome Institute, 2800 Mitchell Dr., Walnut Creek, CA, 94598, USA
| | - Eduardo Blumwald
- Department of Plant Sciences, University of California, 1 Shields Ave, Mail Stop 5, Davis, CA, 95616, USA.
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