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Wang J, Xi L, Wu XN, König S, Rohr L, Neumann T, Weber J, Harter K, Schulze WX. PEP7 acts as a peptide ligand for the receptor kinase SIRK1 to regulate aquaporin-mediated water influx and lateral root growth. MOLECULAR PLANT 2022; 15:1615-1631. [PMID: 36131543 DOI: 10.1016/j.molp.2022.09.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 07/11/2022] [Accepted: 09/19/2022] [Indexed: 06/15/2023]
Abstract
Plant receptors constitute a large protein family that regulates various aspects of development and responses to external cues. Functional characterization of this protein family and the identification of their ligands remain major challenges in plant biology. Previously, we identified plasma membrane-intrinsic sucrose-induced receptor kinase 1 (SIRK1) and Qian Shou kinase 1 (QSK1) as receptor/co-receptor pair involved in the regulation of aquaporins in response to osmotic conditions induced by sucrose. In this study, we identified a member of the elicitor peptide (PEP) family, namely PEP7, as the specific ligand of th receptor kinase SIRK1. PEP7 binds to the extracellular domain of SIRK1 with a binding constant of 1.44 ± 0.79 μM and is secreted to the apoplasm specifically in response to sucrose treatment. Stabilization of a signaling complex involving SIRK1, QSK1, and aquaporins as substrates is mediated by alterations in the external sucrose concentration or by PEP7 application. Moreover, the presence of PEP7 induces the phosphorylation of aquaporins in vivo and enhances water influx into protoplasts. Disturbed water influx, in turn, led to delayed lateral root development in the pep7 mutant. The loss-of-function mutant of SIRK1 is not responsive to external PEP7 treatment regarding kinase activity, aquaporin phosphorylation, water influx activity, and lateral root development. Taken together, our data indicate that the PEP7/SIRK1/QSK1 complex represents a crucial perception and response module that mediates sucrose-controlled water flux in plants and lateral root development.
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Affiliation(s)
- Jiahui Wang
- Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany
| | - Lin Xi
- Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany
| | - Xu Na Wu
- Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany; School of Life Science, Center for Life Sciences, Yunnan University, 650091 Kunming, People's Republic of China
| | - Stefanie König
- Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany
| | - Leander Rohr
- Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany
| | - Theresia Neumann
- Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany
| | - Jan Weber
- Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany
| | - Klaus Harter
- Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany
| | - Waltraud X Schulze
- Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany.
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An Efficient Approach for Separating Essential Oil and Polysaccharides Simultaneously from Fresh Leaves of Guajava by Microwave-Mediated Hydrodistillation with Lithium Salts and Antibacterial Activity of Essential Oil. SEPARATIONS 2022. [DOI: 10.3390/separations9070162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The essential oils and polysaccharides from guava leaves have important functions. In the process of microwave extraction of plant essential oils and polysaccharides, pretreatment with lithium salts solution is helpful to increase the extraction rate. The experiment was conducted using a single factor method. Results were optimized by principal component analysis and response surface optimization. The optimal conditions were: LiCl dosage 45 μmol, microwave time 40 min, liquid-solid ratio 10, homogenization time 4.2 min, liquid-material ratio 10, and microwave irradiation power 700 W. The highest yield of essential oil and polysaccharide were 10.27 ± 0.58 mL/kg dry weight (DW) and 50.31 ± 1.88 g/kg·DW, respectively. Three verification experiments showed that the extraction rate of the microwave method was higher than that of the traditional heating method. In addition, the bacteriostatic zones reached the maximum 23.7 ± 0.11 mm when the concentration was 40 μL/mL, and the above results have practical significance.
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3
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Boursiac Y, Protto V, Rishmawi L, Maurel C. Experimental and conceptual approaches to root water transport. PLANT AND SOIL 2022; 478:349-370. [PMID: 36277078 PMCID: PMC9579117 DOI: 10.1007/s11104-022-05427-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 04/03/2022] [Indexed: 05/05/2023]
Abstract
BACKGROUND Root water transport, which critically contributes to the plant water status and thereby plant productivity, has been the object of extensive experimental and theoretical studies. However, root systems represent an intricate assembly of cells in complex architectures, including many tissues at distinct developmental stages. Our comprehension of where and how molecular actors integrate their function in order to provide the root with its hydraulic properties is therefore still limited. SCOPE Based on current literature and prospective discussions, this review addresses how root water transport can be experimentally measured, what is known about the underlying molecular actors, and how elementary water transport processes are scaled up in numerical/mathematical models. CONCLUSIONS The theoretical framework and experimental procedures on root water transport that are in use today have been established a few decades ago. However, recent years have seen the appearance of new techniques and models with enhanced resolution, down to a portion of root or to the tissue level. These advances pave the way for a better comprehension of the dynamics of water uptake by roots in the soil.
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Affiliation(s)
- Yann Boursiac
- IPSiM, Univ Montpellier, CNRS, INRAE, Institut Agro, 34060 Montpellier, France
| | - Virginia Protto
- IPSiM, Univ Montpellier, CNRS, INRAE, Institut Agro, 34060 Montpellier, France
| | - Louai Rishmawi
- IPSiM, Univ Montpellier, CNRS, INRAE, Institut Agro, 34060 Montpellier, France
| | - Christophe Maurel
- IPSiM, Univ Montpellier, CNRS, INRAE, Institut Agro, 34060 Montpellier, France
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4
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Dumais J. Mechanics and hydraulics of pollen tube growth. THE NEW PHYTOLOGIST 2021; 232:1549-1565. [PMID: 34492127 DOI: 10.1111/nph.17722] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 08/21/2021] [Indexed: 06/13/2023]
Abstract
All kingdoms of life have evolved tip-growing cells able to mine their environment or deliver cargo to remote targets. The basic cellular processes supporting these functions are understood in increasing detail, but the multiple interactions between them lead to complex responses that require quantitative models to be disentangled. Here, I review the equations that capture the fundamental interactions between wall mechanics and cell hydraulics starting with a detailed presentation of James Lockhart's seminal model. The homeostatic feedbacks needed to maintain a steady tip velocity are then shown to offer a credible explanation for the pulsatile growth observed in some tip-growing cells. Turgor pressure emerges as a central variable whose role in the morphogenetic process has been a source of controversy for more than 50 yr. I argue that recasting Lockhart's work as a process of chemical stress relaxation can clarify how cells control tip growth and help us internalise the important but passive role played by turgor pressure in the morphogenetic process.
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Affiliation(s)
- Jacques Dumais
- Faculty of Engineering and Sciences, Universidad Adolfo Ibáñez, Av. Padre Hurtado 750, Viña del Mar, Region of Valparaíso, Chile
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5
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Wu XN, Chu L, Xi L, Pertl-Obermeyer H, Li Z, Sklodowski K, Sanchez-Rodriguez C, Obermeyer G, Schulze WX. Sucrose-induced Receptor Kinase 1 is Modulated by an Interacting Kinase with Short Extracellular Domain. Mol Cell Proteomics 2019; 18:1556-1571. [PMID: 31147492 PMCID: PMC6683012 DOI: 10.1074/mcp.ra119.001336] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 04/08/2019] [Indexed: 12/22/2022] Open
Abstract
Sucrose as a product of photosynthesis is the major carbohydrate translocated from photosynthetic leaves to growing nonphotosynthetic organs such as roots and seeds. These growing tissues, besides carbohydrate supply, require uptake of water through aquaporins to enhance cell expansion during growth. Previous work revealed Sucrose Induced Receptor Kinase, SIRK1, to control aquaporin activity via phosphorylation in response to external sucrose stimulation. Here, we present the regulatory role of AT3G02880 (QSK1), a receptor kinase with a short external domain, in modulation of SIRK1 activity. Our results suggest that SIRK1 autophosphorylates at Ser-744 after sucrose treatment. Autophosphorylated SIRK1 then interacts with and transphosphorylates QSK1 and QSK2. Upon interaction with QSK1, SIRK1 phosphorylates aquaporins at their regulatory C-terminal phosphorylation sites. Consequently, in root protoplast swelling assays, the qsk1qsk2 mutant showed reduced water influx rates under iso-osmotic sucrose stimulation, confirming an involvement in the same signaling pathway as the receptor kinase SIRK1. Large-scale phosphoproteomics comparing single mutant sirk1, qsk1, and double mutant sirk1 qsk1 revealed that aquaporins were regulated by phosphorylation depending on an activated receptor kinase complex of SIRK1, as well as QSK1. QSK1 thereby acts as a coreceptor stabilizing and enhancing SIRK1 activity and recruiting substrate proteins, such as aquaporins.
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Affiliation(s)
- Xu Na Wu
- ‡Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany
| | - Liangcui Chu
- ‡Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany
| | - Lin Xi
- ‡Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany
| | - Heidi Pertl-Obermeyer
- §Molecular Plant Biophysics and Biochemistry, Department of Biosciences, University of Salzburg, 5020 Salzburg, Austria
| | - Zhi Li
- ‡Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany
| | - Kamil Sklodowski
- ¶Department of Biology, ETH Zürich, Universitätsstrasse 2, 8092 Zürich, Switzerland
| | | | - Gerhard Obermeyer
- §Molecular Plant Biophysics and Biochemistry, Department of Biosciences, University of Salzburg, 5020 Salzburg, Austria
| | - Waltraud X Schulze
- ‡Department of Plant Systems Biology, University of Hohenheim, 70593 Stuttgart, Germany.
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Vinnakota R, Ramakrishnan AM, Samdani A, Venugopal MA, Ram BS, Krishnan SN, Murugesan D, Sankaranarayanan K. A comparison of aquaporin function in mediating stomatal aperture gating among drought-tolerant and sensitive varieties of rice (Oryza sativa L.). PROTOPLASMA 2016; 253:1593-1597. [PMID: 26631017 DOI: 10.1007/s00709-015-0916-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 11/23/2015] [Indexed: 05/09/2023]
Abstract
Climate change drastically affects the cultivation of rice, and its production is affected significantly by water stress. Adaptation of a plant to water deficit conditions is orchestrated by efficient water uptake and a stringently regulated water loss. Transpiration remains the major means of water loss from plants and is mediated by microscopic pores called stomata. Stomatal aperture gating is facilitated by ion channels and aquaporins (AQPs) which regulate the turgidity of the guard cells. In a similar manner, efficient water uptake by the roots is regulated by the presence of AQPs in the plasma membrane of root cells. In this study, we compare the efficiency of transmembrane water permeability in guard cells and root protoplasts from drought-tolerant and sensitive varieties of Oryza sativa L. In this report, we studied the transmembrane osmotic water permeability (Pos) of guard cell and root protoplasts of drought-sensitive and tolerant cultivars. The guard cells isolated from the drought-sensitive lowland rice variety ADT-39 show significant low osmotic permeability than the drought-tolerant rice varieties of Anna (lowland) and Dodda Byra Nellu (DBN) (upland local land rice). There is no significant difference in relative gene expression patterns of PIPs (Plasma membrane Intrinsic Proteins "PIP1" and "PIP2" subfamilies) in guard cells isolated from ADT-39 and Anna. While the expression levels of AQP genes remain the same between ADT-39 and Anna, there is a drastic difference in their osmotic permeability in the guard cells in spite of a higher number of stomata in Anna and DBN, hinting at a more efficient gating mechanism of AQP in the stomata of the drought-tolerant varieties studied.
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Affiliation(s)
- Rajesh Vinnakota
- Ion channel Biology Laboratory, AU-KBC Research Centre, Madras Institute of Technology, Anna University, Chromepet, Chennai, 600 044, India
| | - Anantha Maharasi Ramakrishnan
- Ion channel Biology Laboratory, AU-KBC Research Centre, Madras Institute of Technology, Anna University, Chromepet, Chennai, 600 044, India
| | - A Samdani
- Ion channel Biology Laboratory, AU-KBC Research Centre, Madras Institute of Technology, Anna University, Chromepet, Chennai, 600 044, India
| | - M Anjali Venugopal
- Ion channel Biology Laboratory, AU-KBC Research Centre, Madras Institute of Technology, Anna University, Chromepet, Chennai, 600 044, India
| | - B Sri Ram
- Ion channel Biology Laboratory, AU-KBC Research Centre, Madras Institute of Technology, Anna University, Chromepet, Chennai, 600 044, India
| | - S Navaneetha Krishnan
- Ion channel Biology Laboratory, AU-KBC Research Centre, Madras Institute of Technology, Anna University, Chromepet, Chennai, 600 044, India
| | - Dhandapani Murugesan
- Regional Research Station, Tamil Nadu Agricultural University, Paiyur, Krishnagiri, 635112, India
| | - Kavitha Sankaranarayanan
- Ion channel Biology Laboratory, AU-KBC Research Centre, Madras Institute of Technology, Anna University, Chromepet, Chennai, 600 044, India.
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Qing D, Yang Z, Li M, Wong WS, Guo G, Liu S, Guo H, Li N. Quantitative and Functional Phosphoproteomic Analysis Reveals that Ethylene Regulates Water Transport via the C-Terminal Phosphorylation of Aquaporin PIP2;1 in Arabidopsis. MOLECULAR PLANT 2016; 9:158-174. [PMID: 26476206 DOI: 10.1016/j.molp.2015.10.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 08/27/2015] [Accepted: 10/07/2015] [Indexed: 06/05/2023]
Abstract
Ethylene participates in the regulation of numerous cellular events and biological processes, including water loss, during leaf and flower petal wilting. The diverse ethylene responses may be regulated via dynamic interplays between protein phosphorylation/dephosphorylation and ubiquitin/26S proteasome-mediated protein degradation and protease cleavage. To address how ethylene alters protein phosphorylation through multi-furcated signaling pathways, we performed a (15)N stable isotope labelling-based, differential, and quantitative phosphoproteomics study on air- and ethylene-treated ethylene-insensitive Arabidopsis double loss-of-function mutant ein3-1/eil1-1. Among 535 non-redundant phosphopeptides identified, two and four phosphopeptides were up- and downregulated by ethylene, respectively. Ethylene-regulated phosphorylation of aquaporin PIP2;1 is positively correlated with the water flux rate and water loss in leaf. Genetic studies in combination with quantitative proteomics, immunoblot analysis, protoplast swelling/shrinking experiments, and leaf water loss assays on the transgenic plants expressing both the wild-type and S280A/S283A-mutated PIP2;1 in the both Col-0 and ein3eil1 genetic backgrounds suggest that ethylene increases water transport rate in Arabidopsis cells by enhancing S280/S283 phosphorylation at the C terminus of PIP2;1. Unknown kinase and/or phosphatase activities may participate in the initial up-regulation independent of the cellular functions of EIN3/EIL1. This finding contributes to our understanding of ethylene-regulated leaf wilting that is commonly observed during post-harvest storage of plant organs.
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Affiliation(s)
- Dongjin Qing
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Zhu Yang
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Mingzhe Li
- School of Life Science, Peking University, Beijing 100089, China
| | - Wai Shing Wong
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Guangyu Guo
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Shichang Liu
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Hongwei Guo
- School of Life Science, Peking University, Beijing 100089, China
| | - Ning Li
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China.
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8
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Vitali V, Sutka M, Amodeo G, Chara O, Ozu M. The Water to Solute Permeability Ratio Governs the Osmotic Volume Dynamics in Beetroot Vacuoles. FRONTIERS IN PLANT SCIENCE 2016; 7:1388. [PMID: 27695468 PMCID: PMC5024706 DOI: 10.3389/fpls.2016.01388] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 08/31/2016] [Indexed: 05/11/2023]
Abstract
Plant cell vacuoles occupy up to 90% of the cell volume and, beyond their physiological function, are constantly subjected to water and solute exchange. The osmotic flow and vacuole volume dynamics relies on the vacuole membrane -the tonoplast- and its capacity to regulate its permeability to both water and solutes. The osmotic permeability coefficient (Pf ) is the parameter that better characterizes the water transport when submitted to an osmotic gradient. Usually, Pf determinations are made in vitro from the initial rate of volume change, when a fast (almost instantaneous) osmolality change occurs. When aquaporins are present, it is accepted that initial volume changes are only due to water movements. However, in living cells osmotic changes are not necessarily abrupt but gradually imposed. Under these conditions, water flux might not be the only relevant driving force shaping the vacuole volume response. In this study, we quantitatively investigated volume dynamics of isolated Beta vulgaris root vacuoles under progressively applied osmotic gradients at different pH, a condition that modifies the tonoplast Pf . We followed the vacuole volume changes while simultaneously determining the external osmolality time-courses and analyzing these data with mathematical modeling. Our findings indicate that vacuole volume changes, under progressively applied osmotic gradients, would not depend on the membrane elastic properties, nor on the non-osmotic volume of the vacuole, but on water and solute fluxes across the tonoplast. We found that the volume of the vacuole at the steady state is determined by the ratio of water to solute permeabilites (Pf /Ps ), which in turn is ruled by pH. The dependence of the permeability ratio on pH can be interpreted in terms of the degree of aquaporin inhibition and the consequently solute transport modulation. This is relevant in many plant organs such as root, leaves, cotyledons, or stems that perform extensive rhythmic growth movements, which very likely involve considerable cell volume changes within seconds to hours.
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Affiliation(s)
- Victoria Vitali
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Instituto de Biodiversidad y Biología Experimental y Aplicada, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y TécnicasBuenos Aires, Argentina
| | - Moira Sutka
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Instituto de Biodiversidad y Biología Experimental y Aplicada, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y TécnicasBuenos Aires, Argentina
| | - Gabriela Amodeo
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Instituto de Biodiversidad y Biología Experimental y Aplicada, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y TécnicasBuenos Aires, Argentina
| | - Osvaldo Chara
- System Biology Group (SysBio), Institute of Physics of Liquids and Biological Systems (IFLYSIB) CONICET, University of La PlataLa Plata, Argentina
- Center for Information Services and High Performance Computing, Technische Universität DresdenDresden, Germany
| | - Marcelo Ozu
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Instituto de Biodiversidad y Biología Experimental y Aplicada, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y TécnicasBuenos Aires, Argentina
- Departamento de Fisiología y Biofísica, Facultad de Medicina, Instituto de Fisiología y Biofísica (IFIBIO–Houssay), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y TécnicasBuenos Aires, Argentina
- *Correspondence: Marcelo Ozu
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Deokar AA, Tar'an B. Genome-Wide Analysis of the Aquaporin Gene Family in Chickpea ( Cicer arietinum L.). FRONTIERS IN PLANT SCIENCE 2016; 7:1802. [PMID: 27965700 PMCID: PMC5126082 DOI: 10.3389/fpls.2016.01802] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 11/15/2016] [Indexed: 05/18/2023]
Abstract
Aquaporins (AQPs) are essential membrane proteins that play critical role in the transport of water and many other solutes across cell membranes. In this study, a comprehensive genome-wide analysis identified 40 AQP genes in chickpea (Cicer arietinum L.). A complete overview of the chickpea AQP (CaAQP) gene family is presented, including their chromosomal locations, gene structure, phylogeny, gene duplication, conserved functional motifs, gene expression, and conserved promoter motifs. To understand AQP's evolution, a comparative analysis of chickpea AQPs with AQP orthologs from soybean, Medicago, common bean, and Arabidopsis was performed. The chickpea AQP genes were found on all of the chickpea chromosomes, except chromosome 7, with a maximum of six genes on chromosome 6, and a minimum of one gene on chromosome 5. Gene duplication analysis indicated that the expansion of chickpea AQP gene family might have been due to segmental and tandem duplications. CaAQPs were grouped into four subfamilies including 15 NOD26-like intrinsic proteins (NIPs), 13 tonoplast intrinsic proteins (TIPs), eight plasma membrane intrinsic proteins (PIPs), and four small basic intrinsic proteins (SIPs) based on sequence similarities and phylogenetic position. Gene structure analysis revealed a highly conserved exon-intron pattern within CaAQP subfamilies supporting the CaAQP family classification. Functional prediction based on conserved Ar/R selectivity filters, Froger's residues, and specificity-determining positions suggested wide differences in substrate specificity among the subfamilies of CaAQPs. Expression analysis of the AQP genes indicated that some of the genes are tissue-specific, whereas few other AQP genes showed differential expression in response to biotic and abiotic stresses. Promoter profiling of CaAQP genes for conserved cis-acting regulatory elements revealed enrichment of cis-elements involved in circadian control, light response, defense and stress responsiveness reflecting their varying pattern of gene expression and potential involvement in biotic and abiotic stress responses. The current study presents the first detailed genome-wide analysis of the AQP gene family in chickpea and provides valuable information for further functional analysis to infer the role of AQP in the adaptation of chickpea in diverse environmental conditions.
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10
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Shachar-Hill B, Hill AE, Powell J, Skepper JN, Shachar-Hill Y. Mercury-sensitive water channels as possible sensors of water potentials in pollen. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:5195-205. [PMID: 24098048 PMCID: PMC3830494 DOI: 10.1093/jxb/ert311] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The growing pollen tube is central to plant reproduction and is a long-standing model for cellular tip growth in biology. Rapid osmotically driven growth is maintained under variable conditions, which requires osmosensing and regulation. This study explores the mechanism of water entry and the potential role of osmosensory regulation in maintaining pollen growth. The osmotic permeability of the plasmalemma of Lilium pollen tubes was measured from plasmolysis rates to be 1.32±0.31×10(-3) cm s(-1). Mercuric ions reduce this permeability by 65%. Simulations using an osmotic model of pollen tube growth predict that an osmosensor at the cell membrane controls pectin deposition at the cell tip; inhibiting the sensor is predicted to cause tip bursting due to cell wall thinning. It was found that adding mercury to growing pollen tubes caused such a bursting of the tips. The model indicates that lowering the osmotic permeability per se does not lead to bursting but rather to thickening of the tip. The time course of induced bursting showed no time lag and was independent of mercury concentration, compatible with a surface site of action. The submaximal bursting response to intermediate mercuric ion concentration was independent of the concentration of calcium ions, showing that bursting is not due to a competitive inhibition of calcium binding or entry. Bursting with the same time course was also shown by cells growing on potassium-free media, indicating that potassium channels (implicated in mechanosensing) are not involved in the bursting response. The possible involvement of mercury-sensitive water channels as osmosensors and current knowledge of these in pollen cells are discussed.
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Affiliation(s)
| | - Adrian E. Hill
- Department of Physiology, Development and Neuroscience, Cambridge University, Cambridge, UK
- * To whom correspondence should be addressed. E-mail:
| | - Janet Powell
- Multi-Imaging Centre, Cambridge University, Cambridge, UK
| | | | - Yair Shachar-Hill
- Department of Plant Biology, Plant Biology Building, Michigan State University, East Lansing, MI 48824-1312, USA
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11
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Wu XN, Sanchez Rodriguez C, Pertl-Obermeyer H, Obermeyer G, Schulze WX. Sucrose-induced receptor kinase SIRK1 regulates a plasma membrane aquaporin in Arabidopsis. Mol Cell Proteomics 2013; 12:2856-73. [PMID: 23820729 PMCID: PMC3790296 DOI: 10.1074/mcp.m113.029579] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2013] [Revised: 06/30/2013] [Indexed: 11/06/2022] Open
Abstract
The transmembrane receptor kinase family is the largest protein kinase family in Arabidopsis, and it contains the highest fraction of proteins with yet uncharacterized functions. Here, we present functions of SIRK1, a receptor kinase that was previously identified with rapid transient phosphorylation after sucrose resupply to sucrose-starved seedlings. SIRK1 was found to be an active kinase with increasing activity in the presence of an external sucrose supply. In sirk1 T-DNA insertional mutants, the sucrose-induced phosphorylation patterns of several membrane proteins were strongly reduced; in particular, pore-gating phosphorylation sites in aquaporins were affected. SIRK1-GFP fusions were found to directly interact with aquaporins in affinity pull-down experiments on microsomal membrane vesicles. Furthermore, protoplast swelling assays of sirk1 mutants and SIRK1-GFP expressing lines confirmed a direct functional interaction of receptor kinase SIRK1 and aquaporins as substrates for phosphorylation. A lack of SIRK1 expression resulted in the failure of mutant protoplasts to control water channel activity upon changes in external sucrose concentrations. We propose that SIRK1 is involved in the regulation of sucrose-specific osmotic responses through direct interaction with and activation of an aquaporin via phosphorylation and that the duration of this response is controlled by phosphorylation-dependent receptor internalization.
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Affiliation(s)
- Xu Na Wu
- Max Planck Institute for Molecular Plant Physiology, Am Mühlenberg 1, 14476 Golm, Germany
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12
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Hill AE, Shachar-Hill B, Skepper JN, Powell J, Shachar-Hill Y. An osmotic model of the growing pollen tube. PLoS One 2012; 7:e36585. [PMID: 22615784 PMCID: PMC3353927 DOI: 10.1371/journal.pone.0036585] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Accepted: 04/10/2012] [Indexed: 11/19/2022] Open
Abstract
Pollen tube growth is central to the sexual reproduction of plants and is a longstanding model for cellular tip growth. For rapid tip growth, cell wall deposition and hardening must balance the rate of osmotic water uptake, and this involves the control of turgor pressure. Pressure contributes directly to both the driving force for water entry and tip expansion causing thinning of wall material. Understanding tip growth requires an analysis of the coordination of these processes and their regulation. Here we develop a quantitative physiological model which includes water entry by osmosis, the incorporation of cell wall material and the spreading of that material as a film at the tip. Parameters of the model have been determined from the literature and from measurements, by light, confocal and electron microscopy, together with results from experiments made on dye entry and plasmolysis in Lilium longiflorum. The model yields values of variables such as osmotic and turgor pressure, growth rates and wall thickness. The model and its predictive capacity were tested by comparing programmed simulations with experimental observations following perturbations of the growth medium. The model explains the role of turgor pressure and its observed constancy during oscillations; the stability of wall thickness under different conditions, without which the cell would burst; and some surprising properties such as the need for restricting osmotic permeability to a constant area near the tip, which was experimentally confirmed. To achieve both constancy of pressure and wall thickness under the range of conditions observed in steady-state growth the model reveals the need for a sensor that detects the driving potential for water entry and controls the deposition rate of wall material at the tip.
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Affiliation(s)
- Adrian E Hill
- Department of Physiology, Cambridge University, Cambridge, United Kingdom.
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Pertl H, Pöckl M, Blaschke C, Obermeyer G. Osmoregulation in Lilium pollen grains occurs via modulation of the plasma membrane H+ ATPase activity by 14-3-3 proteins. PLANT PHYSIOLOGY 2010; 154:1921-8. [PMID: 20974894 PMCID: PMC2996032 DOI: 10.1104/pp.110.165696] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Accepted: 10/24/2010] [Indexed: 05/18/2023]
Abstract
To allow successful germination and growth of a pollen tube, mature and dehydrated pollen grains (PGs) take up water and have to adjust their turgor pressure according to the water potential of the surrounding stigma surface. The turgor pressure of PGs of lily (Lilium longiflorum) was measured with a modified pressure probe for simultaneous recordings of turgor pressure and membrane potential to investigate the relation between water and electrogenic ion transport in osmoregulation. Upon hyperosmolar shock, the turgor pressure decreased, and the plasma membrane (PM) hyperpolarizes in parallel, whereas depolarization of the PM was observed with hypoosmolar treatment. An acidification and alkalinization of the external medium was monitored after hyper- and hypoosmotic treatments, respectively, and pH changes were blocked by vanadate, indicating a putative role of the PM H(+) ATPase. Indeed, an increase in PM-associated 14-3-3 proteins and an increase in PM H(+) ATPase activity were detected in PGs challenged by hyperosmolar medium. We therefore suggest that in PGs the PM H(+) ATPase via modulation of its activity by 14-3-3 proteins is involved in the regulation of turgor pressure.
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Affiliation(s)
| | | | | | - Gerhard Obermeyer
- Plant Molecular Biophysics and Biochemistry, Department of Molecular Biology, University of Salzburg, 5020 Salzburg, Austria
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Alleva K, Chara O, Sutka MR, Amodeo G. Analysis of the source of heterogeneity in the osmotic response of plant membrane vesicles. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2008; 38:175-84. [PMID: 18769911 DOI: 10.1007/s00249-008-0365-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 08/01/2008] [Accepted: 08/04/2008] [Indexed: 10/21/2022]
Abstract
Plasma membrane vesicles have been widely employed to understand the biophysics of water movements, especially when active aquaporins are present. In general, water permeability coefficients in these preparations outcome from the analysis of the osmotic response of the vesicles by means of light scattering. As from now, this is possible by following a theoretical approach that assumes that scattered light follows a single exponential function and that this behavior is the consequence of vesicle volume changes due to an osmotic challenge. However, some experimental data do not necessarily fit to single exponentials but to double ones. It is argued that the observed double exponential behavior has two possible causes: different vesicle population in terms of permeability or in terms of size distribution. As classical models cannot identify this source of heterogeneity, a mathematical modeling approach was developed based on phenomenological equations of water transport. In the three comparative models presented here, it was assumed that water moves according to an osmotic mechanism across the vesicles, and there is no solute movement across them. Interestingly, when tested in a well described plasma membrane vesicle preparation, the application of these models indicates that the source of heterogeneity in the osmotic response is vesicles having different permeability, clearly discarding the variable size effect. In conclusion, the mathematical approach presented here allows to identify the source of heterogeneity; this information being of particular interest, especially when studying gating mechanisms triggered in water channel activity.
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Affiliation(s)
- Karina Alleva
- Laboratorio de Biomembranas, Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 Piso 7 (C1121ABG), Buenos Aires, Argentina
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Sommer A, Geist B, Da Ines O, Gehwolf R, Schäffner AR, Obermeyer G. Ectopic expression of Arabidopsis thaliana plasma membrane intrinsic protein 2 aquaporins in lily pollen increases the plasma membrane water permeability of grain but not of tube protoplasts. THE NEW PHYTOLOGIST 2008; 180:787-97. [PMID: 18761636 PMCID: PMC2999827 DOI: 10.1111/j.1469-8137.2008.02607.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
To investigate the role of aquaporin-mediated water transport during pollen grain germination and tube growth, Arabidopsis thaliana plasma membrane intrinsic proteins (PIPs) were expressed in pollen of Lilium longiflorum (lily). Successful expression of AtPIPs in particle-bombarded lily pollen grains was monitored by co-expression with fluorescent proteins and single-cell RT-PCR, and by measuring the water permeability coefficient (P(os)) in swelling assays using protoplasts prepared from transformed pollen grains and tubes. Expression of AtPIP1;1 and AtPIP1;2 in pollen grains resulted in P(os) values similar to those measured in nontransformed pollen grain protoplasts (6.65 +/- 2.41 microm s(-1)), whereas expression of AtPIP2 significantly increased P(os) (AtPIP2;1, 13.79 +/- 6.38; AtPIP2;2, 10.16 +/- 3.30 microm s(-1)). Transformation with combinations of AtPIP1 and AtPIP2 did not further enhance P(os). Native pollen tube protoplasts showed higher P(os) values (13.23 +/- 4.14 microm s(-1)) than pollen grain protoplasts but expression of AtPIP2;1 (18.85 +/- 7.60 microm s(-1)) did not significantly increase their P(os) values. Expression of none of the tested PIPs had any effect on pollen tube growth rates. The ectopic expression of AtPIP2s in lily pollen increased the water permeability of the plasma membrane in pollen grains, but not in pollen tubes. The measured endogenous water permeability does not limit water uptake during tube growth, but has to be regulated to prevent tube bursting.
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Affiliation(s)
- Aniela Sommer
- Molecular Plant Biophysics and Biotechnology, Department of Molecular Biology, University of Salzburg, Billrothstr. 11, 5020 Salzburg, Austria
| | - Birgit Geist
- Institute of Biochemical Plant Pathology, Helmholtz Zentrum München – German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany
| | - Olivier Da Ines
- Institute of Biochemical Plant Pathology, Helmholtz Zentrum München – German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany
| | - Renate Gehwolf
- Molecular Plant Biophysics and Biotechnology, Department of Molecular Biology, University of Salzburg, Billrothstr. 11, 5020 Salzburg, Austria
| | - Anton R. Schäffner
- Institute of Biochemical Plant Pathology, Helmholtz Zentrum München – German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany
| | - Gerhard Obermeyer
- Molecular Plant Biophysics and Biotechnology, Department of Molecular Biology, University of Salzburg, Billrothstr. 11, 5020 Salzburg, Austria
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