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Christophe Maurel - One of the best experts on this subject based on the ideXlab platform.
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Plant Aquaporins
2018Co-Authors: Lionel Verdoucq, Christophe MaurelAbstract:Aquaporins are membrane channels that facilitate the transport of water and small neutral molecules across biological membranes of most living organisms. Plant Aquaporins constitute a large family of evolutionarily related channels showing a high diversity of cellular localisations, transport selectivity, and regulation properties. Plant Aquaporins can transport various small solutes in addition to water, such as hydrogen peroxide, ammonia, urea, metalloids, gases and even ions, indicating a wide range of cellular functions. At the cellular level, plant Aquaporins are subjected to various regulation mechanisms leading to active/inactive channels in their target membranes. Structure–function studies have been instrumental to address the molecular and cellular mechanisms of plant aquaporin gating and subcellular trafficking. We present our current knowledge on their co- and post-translational modifications and more specifically discuss the importance of lipidic environment in aquaporin function. Overall, the present chapter shows how the 25 years of research performed since the discovery of Aquaporins has established their crucial role in plants
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Aquaporins and plant transpiration.
Plant Cell and Environment, 2016Co-Authors: Christophe Maurel, Lionel Verdoucq, Olivier RodriguesAbstract:Although transpiration and Aquaporins have long been identified as two key components influencing plant water status, it is only recently that their relations have been investigated in detail. The present review first examines the various facets of aquaporin function in stomatal guard cells and shows that it involves transport of water but also of other molecules such as carbon dioxide and hydrogen peroxide. At the whole plant level, changes in tissue hydraulics mediated by root and shoot Aquaporins can indirectly impact plant transpiration. Recent studies also point to a feedback effect of transpiration on aquaporin function. These mechanisms may contribute to the difference between isohydric and anisohydric stomatal regulation of leaf water status. The contribution of Aquaporins to transpiration control goes far beyond the issue of water transport during stomatal movements and involves emerging cellular and long-distance signalling mechanisms which ultimately act on plant growth.
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Aquaporins in Plants.
Physiological Reviews, 2015Co-Authors: Christophe Maurel, Veronique Santoni, Yann Boursiac, Doan Luu, Zaigham Shahzad, Lionel VerdoucqAbstract:Aquaporins are membrane channels that facilitate the transport of water and small neutral molecules across biological membranes of most living organisms. In plants, Aquaporins occur as multiple isoforms reflecting a high diversity of cellular localizations, transport selectivity, and regulation properties. Plant Aquaporins are localized in the plasma membrane, endoplasmic reticulum, vacuoles, plastids and, in some species, in membrane compartments interacting with symbiotic organisms. Plant Aquaporins can transport various physiological substrates in addition to water. Of particular relevance for plants is the transport of dissolved gases such as carbon dioxide and ammonia or metalloids such as boron and silicon. Structure-function studies are developed to address the molecular and cellular mechanisms of plant aquaporin gating and subcellular trafficking. Phosphorylation plays a central role in these two processes. These mechanisms allow aquaporin regulation in response to signaling intermediates such as cytosolic pH and calcium, and reactive oxygen species. Combined genetic and physiological approaches are now integrating this knowledge, showing that Aquaporins play key roles in hydraulic regulation in roots and leaves, during drought but also in response to stimuli as diverse as flooding, nutrient availability, temperature, or light. A general hydraulic control of plant tissue expansion by Aquaporins is emerging, and their role in key developmental processes (seed germination, emergence of lateral roots) has been established. Plants with genetically altered aquaporin functions are now tested for their ability to improve plant tolerance to stresses. In conclusion, research on Aquaporins delineates ever expanding fields in plant integrative biology thereby establishing their crucial role in plants.
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plant Aquaporins roles in plant physiology
Biochimica et Biophysica Acta, 2014Co-Authors: Guowei Li, Veronique Santoni, Christophe MaurelAbstract:Abstract Background Aquaporins are membrane channels that facilitate the transport of water and small neutral molecules across biological membranes of most living organisms. Scope of review Here, we present comprehensive insights made on plant Aquaporins in recent years, pointing to their molecular and physiological specificities with respect to animal or microbial counterparts. Major conclusions In plants, Aquaporins occur as multiple isoforms reflecting a high diversity of cellular localizations and various physiological substrates in addition to water. Of particular relevance for plants is the transport by Aquaporins of dissolved gases such as carbon dioxide or metalloids such as boric or silicic acid. The mechanisms that determine the gating and subcellular localization of plant Aquaporins are extensively studied. They allow aquaporin regulation in response to multiple environmental and hormonal stimuli. Thus, Aquaporins play key roles in hydraulic regulation and nutrient transport in roots and leaves. They contribute to several plant growth and developmental processes such as seed germination or emergence of lateral roots. General significance Plants with genetically altered aquaporin functions are now tested for their ability to improve plant resistance to stresses. This article is part of a Special Issue entitled Aquaporins.
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Coordinated Post-translational Responses of Aquaporins to Abiotic and Nutritional Stimuli in Arabidopsis Roots.
Molecular and Cellular Proteomics, 2013Co-Authors: Magali Di Pietro, Christophe Maurel, Jérôme Vialaret, Sonia Hem, Karine Prado, Michel Rossignol, Veronique SantoniAbstract:In plants, Aquaporins play a crucial role in regulating root water transport in response to environmental and physiological cues. Controls achieved at the post-translational level are thought to be of critical importance for regulating aquaporin function. To investigate the general molecular mechanisms involved, we performed, using the model species Arabidopsis, a comprehensive proteomic analysis of root Aquaporins in a large set of physiological contexts. We identified nine physiological treatments that modulate root hydraulics in time frames of minutes (NO and H2O2 treatments), hours (mannitol and NaCl treatments, exposure to darkness and reversal with sucrose, phosphate supply to phosphate-starved roots), or days (phosphate or nitrogen starvation). All treatments induced inhibition of root water transport except for sucrose supply to dark-grown plants and phosphate resupply to phosphate-starved plants, which had opposing effects. Using a robust label-free quantitative proteomic methodology, we identified 12 of 13 plasma membrane intrinsic protein (PIP) aquaporin isoforms, 4 of the 10 tonoplast intrinsic protein isoforms, and a diversity of post-translational modifications including phosphorylation, methylation, deamidation, and acetylation. A total of 55 aquaporin peptides displayed significant changes after treatments and enabled the identification of specific and as yet unknown patterns of response to stimuli. The data show that the regulation of PIP and tonoplast intrinsic protein abundance was involved in response to a few treatments (i.e. NaCl, NO, and nitrate starvation), whereas changes in the phosphorylation status of PIP Aquaporins were positively correlated to changes in root hydraulic conductivity in the whole set of treatments. The identification of in vivo deamidated forms of Aquaporins and their stimulus-induced changes in abundance may reflect a new mechanism of aquaporin regulation. The overall work provides deep insights into the in vivo post-translational events triggered by environmental constraints and their possible role in regulating plant water status.
Alan S. Verkman - One of the best experts on this subject based on the ideXlab platform.
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Aquaporins in Clinical Medicine
Annual review of medicine, 2012Co-Authors: Alan S. VerkmanAbstract:The Aquaporins are a family of membrane water channels, some of which also transport glycerol. They are involved in a wide range of physiological functions (including water/salt homeostasis, exocrine fluid secretion, and epidermal hydration) and human diseases (including glaucoma, cancer, epilepsy, and obesity). At the cellular level, aquaporin-mediated osmotic water transport across cell plasma membranes facilitates transepithelial fluid transport, cell migration, and neuroexcitation; aquaporin-mediated glycerol transport regulates cell proliferation, adipocyte metabolism, and epidermal water retention. Genetic diseases caused by loss-of-function mutations in Aquaporins include nephrogenic diabetes insipidus and congenital cataracts. The neuroinflammatory demyelinating disease neuromyelitis optica is marked by pathogenic autoantibodies against astrocyte water channel aquaporin-4. There remain broad opportunities for the development of aquaporin-based diagnostics and therapeutics. Disease-relevant aquaporin polymorphisms are beginning to be explored. There is great promise in the development of small-molecule aquaporin modulators for therapy of some types of refractory edema, brain swelling, neuroinflammation, glaucoma, epilepsy, cancer, pain, and obesity.
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Aquaporins in Clinical Medicine
Annual Review of Medicine, 2012Co-Authors: Alan S. VerkmanAbstract:The Aquaporins are a family of membrane water channels, some of which also transport glycerol. They are involved in a wide range of physiological functions (including water/salt homeostasis, exocrine fluid secretion, and epidermal hydration) and human diseases (including glaucoma, cancer, epilepsy, and obesity). At the cellular level, aquaporin-mediated osmotic water transport across cell plasma membranes facilitates transepithelial fluid transport, cell migration, and neuroexcitation; aquaporin-mediated glycerol transport regulates cell proliferation, adipocyte metabolism, and epidermal water retention. Genetic diseases caused by loss-of-function mutations in Aquaporins include nephrogenic diabetes insipidus and congenital cataracts. The neuroinflammatory demyelinating disease neuromyelitis optica is marked by pathogenic autoantibodies against astrocyte water channel aquaporin-4. There remain broad opportunities for the development of aquaporin-based diagnostics and therapeutics. Disease-relevant aquapor...
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Aquaporins: translating bench research to human disease.
The Journal of Experimental Biology, 2009Co-Authors: Alan S. VerkmanAbstract:There is considerable potential for translating knowledge of aquaporin structure, function and physiology to the clinic. One area is in aquaporin-based diagnostics. The discovery of AQP4 autoantibodies as a marker of the neuromyelitis optica form of multiple sclerosis has allowed precise diagnosis of this disease. Other aquaporin-based diagnostics are possible. Another area is in aquaporin-based genetics. Genetic diseases caused by loss-of-function mutations in Aquaporins include nephrogenic diabetes insipidus and cataracts, and functionally significant aquaporin polymorphisms are beginning to be explored. Perhaps of greatest translational potential is aquaporin-based therapeutics. Information largely from aquaporin knockout mice has implicated key roles of aquaporin-facilitated water transport in transepithelial fluid transport (urinary concentrating, gland fluid secretion), water movement into and out of the brain, cell migration (angiogenesis, tumor metastasis, wound healing) and neural function (sensory signaling, seizures). A subset of Aquaporins that transport both water and glycerol, the `aquaglyceroporins', regulate glycerol content in epidermal, fat and other tissues, and are involved in skin hydration, cell proliferation, carcinogenesis and fat metabolism. Aquaporin-based modulator drugs are predicted to be of broad potential utility in the treatment of edematous states, cancer, obesity, wound healing, epilepsy and glaucoma. These exciting possibilities and their associated challenges are reviewed.
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Applications of aquaporin inhibitors.
Drug News & Perspectives, 2001Co-Authors: Alan S. VerkmanAbstract:: The Aquaporins are a family of small, integral membrane proteins that function as plasma membrane transporters of water and in some cases small polar solutes such as glycerol. There are at least 10 distinct Aquaporins in mammals with specific patterns of expression in epithelial, endothelial and other tissues. Recent studies in aquaporin-null mice have indicated key roles for certain Aquaporins in the urinary concentrating mechanism, fluid secretion by glands, brain swelling, skin moisture, hearing and vision, and gastrointestinal absorption. The only known inhibitors of some Aquaporins are mercurial sulfhydryl-reactive compounds, which are too toxic and nonspecific for use in vivo. Small-molecule or peptide aquaporin blockers have potential applications in the treatment of disorders of fluid/pressure homeostasis such as heart failure, hypertension, brain swelling and glaucoma.
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Gastrointestinal Phenotype of Aquaporin Knockout Mice
Molecular Biology and Physiology of Water and Solute Transport, 2000Co-Authors: Alan S. VerkmanAbstract:Fluid transport is a major function of the gastrointestinal (GI) tract. In humans, more than 9 litres/day of fluid are absorbed or secreted across epithelia and endothelia in salivary gland, stomach, the hepatobiliary tract, pancreas, small intestine and colon (Figure 1). There is increasing evidence that aquaporin water channels (AQPs) are involved in GI fluid transport and digestive function. At least seven Aquaporins are expressed in various epithelia and endothelia in the GI system. There are functional data that some GI cell types expressing Aquaporins have high or regulated water permeability. Phenotypic analysis of transgenic knockout mice lacking various Aquaporins has provided direct evidence that Aquaporins are involved in saliva secretion, dietary fat processing, and colon fluid transport. This brief chapter summarizes recent progress on the GI phenotype of aquaporin knockout mice.
Veronique Santoni - One of the best experts on this subject based on the ideXlab platform.
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Plant Aquaporin Posttranslational Regulation
Plant Aquaporins, 2017Co-Authors: Veronique SantoniAbstract:Posttranslational modifications are mechanisms that modulate and control the functions of proteins. The development of mass spectrometry methodology allows description of the extent of posttranslational modifications affecting plant Aquaporins. Hence, more than 70 phosphorylation sites are described in several aquaporin isoforms belonging to PIP, TIP, and NIP groups across different species, and several kinases have been characterized. N-terminal protein modifications also occur on plant Aquaporins as well as deamidation, glycosylation, methylation, and ubiquitination. This chapter summarizes the knowledge about aquaporin posttranslational modifications and their implication in aquaporin function.
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Aquaporins in Plants.
Physiological Reviews, 2015Co-Authors: Christophe Maurel, Veronique Santoni, Yann Boursiac, Doan Luu, Zaigham Shahzad, Lionel VerdoucqAbstract:Aquaporins are membrane channels that facilitate the transport of water and small neutral molecules across biological membranes of most living organisms. In plants, Aquaporins occur as multiple isoforms reflecting a high diversity of cellular localizations, transport selectivity, and regulation properties. Plant Aquaporins are localized in the plasma membrane, endoplasmic reticulum, vacuoles, plastids and, in some species, in membrane compartments interacting with symbiotic organisms. Plant Aquaporins can transport various physiological substrates in addition to water. Of particular relevance for plants is the transport of dissolved gases such as carbon dioxide and ammonia or metalloids such as boron and silicon. Structure-function studies are developed to address the molecular and cellular mechanisms of plant aquaporin gating and subcellular trafficking. Phosphorylation plays a central role in these two processes. These mechanisms allow aquaporin regulation in response to signaling intermediates such as cytosolic pH and calcium, and reactive oxygen species. Combined genetic and physiological approaches are now integrating this knowledge, showing that Aquaporins play key roles in hydraulic regulation in roots and leaves, during drought but also in response to stimuli as diverse as flooding, nutrient availability, temperature, or light. A general hydraulic control of plant tissue expansion by Aquaporins is emerging, and their role in key developmental processes (seed germination, emergence of lateral roots) has been established. Plants with genetically altered aquaporin functions are now tested for their ability to improve plant tolerance to stresses. In conclusion, research on Aquaporins delineates ever expanding fields in plant integrative biology thereby establishing their crucial role in plants.
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plant Aquaporins roles in plant physiology
Biochimica et Biophysica Acta, 2014Co-Authors: Guowei Li, Veronique Santoni, Christophe MaurelAbstract:Abstract Background Aquaporins are membrane channels that facilitate the transport of water and small neutral molecules across biological membranes of most living organisms. Scope of review Here, we present comprehensive insights made on plant Aquaporins in recent years, pointing to their molecular and physiological specificities with respect to animal or microbial counterparts. Major conclusions In plants, Aquaporins occur as multiple isoforms reflecting a high diversity of cellular localizations and various physiological substrates in addition to water. Of particular relevance for plants is the transport by Aquaporins of dissolved gases such as carbon dioxide or metalloids such as boric or silicic acid. The mechanisms that determine the gating and subcellular localization of plant Aquaporins are extensively studied. They allow aquaporin regulation in response to multiple environmental and hormonal stimuli. Thus, Aquaporins play key roles in hydraulic regulation and nutrient transport in roots and leaves. They contribute to several plant growth and developmental processes such as seed germination or emergence of lateral roots. General significance Plants with genetically altered aquaporin functions are now tested for their ability to improve plant resistance to stresses. This article is part of a Special Issue entitled Aquaporins.
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Coordinated Post-translational Responses of Aquaporins to Abiotic and Nutritional Stimuli in Arabidopsis Roots.
Molecular and Cellular Proteomics, 2013Co-Authors: Magali Di Pietro, Christophe Maurel, Jérôme Vialaret, Sonia Hem, Karine Prado, Michel Rossignol, Veronique SantoniAbstract:In plants, Aquaporins play a crucial role in regulating root water transport in response to environmental and physiological cues. Controls achieved at the post-translational level are thought to be of critical importance for regulating aquaporin function. To investigate the general molecular mechanisms involved, we performed, using the model species Arabidopsis, a comprehensive proteomic analysis of root Aquaporins in a large set of physiological contexts. We identified nine physiological treatments that modulate root hydraulics in time frames of minutes (NO and H2O2 treatments), hours (mannitol and NaCl treatments, exposure to darkness and reversal with sucrose, phosphate supply to phosphate-starved roots), or days (phosphate or nitrogen starvation). All treatments induced inhibition of root water transport except for sucrose supply to dark-grown plants and phosphate resupply to phosphate-starved plants, which had opposing effects. Using a robust label-free quantitative proteomic methodology, we identified 12 of 13 plasma membrane intrinsic protein (PIP) aquaporin isoforms, 4 of the 10 tonoplast intrinsic protein isoforms, and a diversity of post-translational modifications including phosphorylation, methylation, deamidation, and acetylation. A total of 55 aquaporin peptides displayed significant changes after treatments and enabled the identification of specific and as yet unknown patterns of response to stimuli. The data show that the regulation of PIP and tonoplast intrinsic protein abundance was involved in response to a few treatments (i.e. NaCl, NO, and nitrate starvation), whereas changes in the phosphorylation status of PIP Aquaporins were positively correlated to changes in root hydraulic conductivity in the whole set of treatments. The identification of in vivo deamidated forms of Aquaporins and their stimulus-induced changes in abundance may reflect a new mechanism of aquaporin regulation. The overall work provides deep insights into the in vivo post-translational events triggered by environmental constraints and their possible role in regulating plant water status.
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The cellular dynamics of plant aquaporin expression and functions.
Current Opinion in Plant Biology, 2009Co-Authors: Christophe Maurel, Veronique Santoni, Doan-trung Luu, Michael M Wudick, Lionel VerdoucqAbstract:Aquaporins are channel proteins that facilitate the transport of water and small neutral molecules, including gases, across cell membranes of most of the living organisms. Integrative studies have stressed the role of Aquaporins in maintaining the whole plant water and nutrient status. Cellular aspects of plant aquaporin functions and regulations are also extensively investigated. The present review provides a glance at recent progresses in this area. One first direction concerns the mechanisms that determine aquaporin targeting to specific subcellular membranes and a dynamic and stimulus-dependent control of their density in these membranes. The regulation of aquaporin opening and closing and its links to cell signalling cascades are also discussed. Multiple cellular functions are now attributed to plant Aquaporins. They include the dynamic equilibration and subcellular partitioning of their various substrates and a contribution to cell expansion and possibly cell division.
Ralf Kaldenhoff - One of the best experts on this subject based on the ideXlab platform.
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Preparative scale production of functional mouse aquaporin 4 using different cell-free expression modes.
PloS one, 2010Co-Authors: Lei Kai, Ralf Kaldenhoff, Jiazhang Lian, Xiangcheng Zhu, Volker Dötsch, Frank Bernhard, Peilin CenAbstract:The continuous progress in the structural and functional characterization of Aquaporins increasingly attracts attention to study their roles in certain mammalian diseases. Although several structures of Aquaporins have already been solved by crystallization, the challenge of producing sufficient amounts of functional proteins still remains. CF (cell free) expression has emerged in recent times as a promising alternative option in order to synthesize large quantities of membrane proteins, and the focus of this report was to evaluate the potential of this technique for the production of eukaryotic Aquaporins. We have selected the mouse aquaporin 4 as a representative of mammalian Aquaporins. The protein was synthesized in an E. coli extract based cell-free system with two different expression modes, and the efficiencies of two modes were compared. In both, the P-CF (cell-free membrane protein expression as precipitate) mode generating initial aquaporin precipitates as well as in the D-CF (cell-free membrane protein expression in presence of detergent) mode, generating directly detergent solubilized samples, we were able to obtain mg amounts of protein per ml of cell-free reaction. Purified aquaporin samples solubilized in different detergents were reconstituted into liposomes, and analyzed for the water channel activity. The calculated Pf value of proteoliposome samples isolated from the D-CF mode was 133 µm/s at 10°C, which was 5 times higher as that of the control. A reversible inhibitory effect of mercury chloride was observed, which is consistent with previous observations of in vitro reconstituted aquaporin 4. In this study, a fast and convenient protocol was established for functional expression of Aquaporins, which could serve as basis for further applications such as water filtration.
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Characterization of plant Aquaporins.
Methods in Enzymology, 2007Co-Authors: Ralf Kaldenhoff, Adam Bertl, Beate Otto, Menachem Moshelion, Norbert UehleinAbstract:Plants have been reported to contain a large set of Aquaporins (38 for Arabidopsis), which has been divided into four subfamilies on the basis of similarities in their amino acid sequences. They belong to the large superfamily of major intrinsic proteins (MIP), which was the basis for the nomenclature PIP, TIP, and NIP, also indicating the subcellular localization plasma membrane, tonoplast, and nodule of the respective founding member. The fourth subfamily of small and basic intrinsic proteins is not well characterized so far. The increasing number of reports dealing with various aspects of plant Aquaporins is starting to advance our understanding of aquaporin biology in plants. Fundamental questions include: what is the basic function of the different plant Aquaporins, what is their primary substrate, and what is the consequence of function/malfunction of a particular aquaporin for the overall function of the plant? Biochemical and biophysical techniques can be employed to get information on the basic functional characteristics of plant Aquaporins. An impressive set of techniques has been used to study aquaporin function on molecular, subcellular, and cellular levels in plants, as well as in heterologous expression systems. The physiological role of Aquaporins in plants is much less well understood, but reports unraveling the physiological role of Aquaporins, mainly employing genetic techniques and functional measurement on the whole plant level, are emerging. The goal of this chapter is to give an overview on the applied methods, together with some exemplary findings.
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Aquaporins and biological rhythm
Biological Rhythm Research, 2006Co-Authors: Norbert Uehlein, Ralf KaldenhoffAbstract:Abstract Aquaporins are membrane-intrinsic proteins that facilitate membrane transport of water and small solutes or even gases. Aquaporin genes are found in almost all living organisms. In plants the proteins account for water uptake and transport as well as CO2 availability for photosynthesis. These processes are subjected to diurnal or circadian regimes. Expression and even function of Aquaporins also follows day – night rhythms. Significance of aquaporin function in chronobiology has been provided by recent publications, which are summarised here. Examples of the significance of Aquaporins in processes related to chronobiology are given for root water transport and leaf movement in several plant species.
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Functional aquaporin diversity in plants.
Biochimica et Biophysica Acta, 2006Co-Authors: Ralf Kaldenhoff, Matthias FischerAbstract:Due to the fact that most plants are immobile, a rapid response of physiological processes to changing environmental conditions is essential for their survival. Thus, in comparison to many other organisms, plants might need a more sophisticated tuning of water balance. Among others, this is reflected by the comparable large amount of aquaporin genes in plant genomes. So far, Aquaporins were shown to be involved in many physiological processes like root water uptake, reproduction or photosynthesis. Their classification as simple water pores has changed according to their molecular function into channels permeable for water, small solutes and/or gases. An adjustment of the corresponding physiological process could be achieved by regulation mechanisms. Concerning Aquaporins these range from posttranslational modification, molecular trafficking to heteromerization of aquaporin isoforms. The aim of this review is to underline the function of the four plant aquaporin family subclasses with regard to the substrate specificity, regulation and physiological relevance.
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The Aquaporins.
Genome biology, 2006Co-Authors: Elisabeth Kruse, Norbert Uehlein, Ralf KaldenhoffAbstract:Water is the major component of all living cells, and efficient regulation of water homeostasis is essential for many biological processes. The mechanism by which water passes through biological membranes was a matter of debate until the discovery of the aquaporin water channels. Aquaporins are intrinsic membrane proteins characterized by six transmembrane helices that selectively allow water or other small uncharged molecules to pass along the osmotic gradient. In addition, recent observations show that some Aquaporins also facilitate the transport of volatile substances, such as carbon dioxide (CO2) and ammonia (NH3), across membranes. Aquaporins usually form tetramers, with each monomer defining a single pore. Aquaporin-related proteins are found in all organisms, from archaea to mammals. In both uni- and multicellular organisms, numerous isoforms have been identified that are differentially expressed and modified by post-translational processes, thus allowing fine-tuned tissue-specific osmoregulation. In mammals, Aquaporins are involved in multiple physiological processes, including kidney and salivary gland function. They are associated with several clinical disorders, such as kidney dysfunction, loss of vision and brain edema.
Lionel Verdoucq - One of the best experts on this subject based on the ideXlab platform.
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Plant Aquaporins
2018Co-Authors: Lionel Verdoucq, Christophe MaurelAbstract:Aquaporins are membrane channels that facilitate the transport of water and small neutral molecules across biological membranes of most living organisms. Plant Aquaporins constitute a large family of evolutionarily related channels showing a high diversity of cellular localisations, transport selectivity, and regulation properties. Plant Aquaporins can transport various small solutes in addition to water, such as hydrogen peroxide, ammonia, urea, metalloids, gases and even ions, indicating a wide range of cellular functions. At the cellular level, plant Aquaporins are subjected to various regulation mechanisms leading to active/inactive channels in their target membranes. Structure–function studies have been instrumental to address the molecular and cellular mechanisms of plant aquaporin gating and subcellular trafficking. We present our current knowledge on their co- and post-translational modifications and more specifically discuss the importance of lipidic environment in aquaporin function. Overall, the present chapter shows how the 25 years of research performed since the discovery of Aquaporins has established their crucial role in plants
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Aquaporins and plant transpiration.
Plant Cell and Environment, 2016Co-Authors: Christophe Maurel, Lionel Verdoucq, Olivier RodriguesAbstract:Although transpiration and Aquaporins have long been identified as two key components influencing plant water status, it is only recently that their relations have been investigated in detail. The present review first examines the various facets of aquaporin function in stomatal guard cells and shows that it involves transport of water but also of other molecules such as carbon dioxide and hydrogen peroxide. At the whole plant level, changes in tissue hydraulics mediated by root and shoot Aquaporins can indirectly impact plant transpiration. Recent studies also point to a feedback effect of transpiration on aquaporin function. These mechanisms may contribute to the difference between isohydric and anisohydric stomatal regulation of leaf water status. The contribution of Aquaporins to transpiration control goes far beyond the issue of water transport during stomatal movements and involves emerging cellular and long-distance signalling mechanisms which ultimately act on plant growth.
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Aquaporins in Plants.
Physiological Reviews, 2015Co-Authors: Christophe Maurel, Veronique Santoni, Yann Boursiac, Doan Luu, Zaigham Shahzad, Lionel VerdoucqAbstract:Aquaporins are membrane channels that facilitate the transport of water and small neutral molecules across biological membranes of most living organisms. In plants, Aquaporins occur as multiple isoforms reflecting a high diversity of cellular localizations, transport selectivity, and regulation properties. Plant Aquaporins are localized in the plasma membrane, endoplasmic reticulum, vacuoles, plastids and, in some species, in membrane compartments interacting with symbiotic organisms. Plant Aquaporins can transport various physiological substrates in addition to water. Of particular relevance for plants is the transport of dissolved gases such as carbon dioxide and ammonia or metalloids such as boron and silicon. Structure-function studies are developed to address the molecular and cellular mechanisms of plant aquaporin gating and subcellular trafficking. Phosphorylation plays a central role in these two processes. These mechanisms allow aquaporin regulation in response to signaling intermediates such as cytosolic pH and calcium, and reactive oxygen species. Combined genetic and physiological approaches are now integrating this knowledge, showing that Aquaporins play key roles in hydraulic regulation in roots and leaves, during drought but also in response to stimuli as diverse as flooding, nutrient availability, temperature, or light. A general hydraulic control of plant tissue expansion by Aquaporins is emerging, and their role in key developmental processes (seed germination, emergence of lateral roots) has been established. Plants with genetically altered aquaporin functions are now tested for their ability to improve plant tolerance to stresses. In conclusion, research on Aquaporins delineates ever expanding fields in plant integrative biology thereby establishing their crucial role in plants.
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The cellular dynamics of plant aquaporin expression and functions.
Current Opinion in Plant Biology, 2009Co-Authors: Christophe Maurel, Veronique Santoni, Doan-trung Luu, Michael M Wudick, Lionel VerdoucqAbstract:Aquaporins are channel proteins that facilitate the transport of water and small neutral molecules, including gases, across cell membranes of most of the living organisms. Integrative studies have stressed the role of Aquaporins in maintaining the whole plant water and nutrient status. Cellular aspects of plant aquaporin functions and regulations are also extensively investigated. The present review provides a glance at recent progresses in this area. One first direction concerns the mechanisms that determine aquaporin targeting to specific subcellular membranes and a dynamic and stimulus-dependent control of their density in these membranes. The regulation of aquaporin opening and closing and its links to cell signalling cascades are also discussed. Multiple cellular functions are now attributed to plant Aquaporins. They include the dynamic equilibration and subcellular partitioning of their various substrates and a contribution to cell expansion and possibly cell division.