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Bezerra-Neto JP, de Araújo FC, Ferreira-Neto JRC, da Silva MD, Pandolfi V, Aburjaile FF, Sakamoto T, de Oliveira Silva RL, Kido EA, Barbosa Amorim LL, Ortega JM, Benko-Iseppon AM. Plant Aquaporins: Diversity, Evolution and Biotechnological Applications. Curr Protein Pept Sci 2019; 20:368-395. [PMID: 30387391 DOI: 10.2174/1389203720666181102095910] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 10/24/2018] [Accepted: 10/30/2018] [Indexed: 12/20/2022]
Abstract
The plasma membrane forms a permeable barrier that separates the cytoplasm from the external environment, defining the physical and chemical limits in each cell in all organisms. The movement of molecules and ions into and out of cells is controlled by the plasma membrane as a critical process for cell stability and survival, maintaining essential differences between the composition of the extracellular fluid and the cytosol. In this process aquaporins (AQPs) figure as important actors, comprising highly conserved membrane proteins that carry water, glycerol and other hydrophilic molecules through biomembranes, including the cell wall and membranes of cytoplasmic organelles. While mammals have 15 types of AQPs described so far (displaying 18 paralogs), a single plant species can present more than 120 isoforms, providing transport of different types of solutes. Such aquaporins may be present in the whole plant or can be associated with different tissues or situations, including biotic and especially abiotic stresses, such as drought, salinity or tolerance to soils rich in heavy metals, for instance. The present review addresses several aspects of plant aquaporins, from their structure, classification, and function, to in silico methodologies for their analysis and identification in transcriptomes and genomes. Aspects of evolution and diversification of AQPs (with a focus on plants) are approached for the first time with the aid of the LCA (Last Common Ancestor) analysis. Finally, the main practical applications involving the use of AQPs are discussed, including patents and future perspectives involving this important protein family.
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Affiliation(s)
- João P Bezerra-Neto
- Universidade Federal de Pernambuco, Genetics Department, Center of Biosciences, Av. Prof. Moraes Rego, 1235, 50.670-423, Recife, Pernambuco, Brazil
| | - Flávia Czekalski de Araújo
- Universidade Federal de Pernambuco, Genetics Department, Center of Biosciences, Av. Prof. Moraes Rego, 1235, 50.670-423, Recife, Pernambuco, Brazil
| | - José R C Ferreira-Neto
- Universidade Federal de Pernambuco, Genetics Department, Center of Biosciences, Av. Prof. Moraes Rego, 1235, 50.670-423, Recife, Pernambuco, Brazil
| | - Manassés D da Silva
- Universidade Federal de Pernambuco, Genetics Department, Center of Biosciences, Av. Prof. Moraes Rego, 1235, 50.670-423, Recife, Pernambuco, Brazil
| | - Valesca Pandolfi
- Universidade Federal de Pernambuco, Genetics Department, Center of Biosciences, Av. Prof. Moraes Rego, 1235, 50.670-423, Recife, Pernambuco, Brazil
| | - Flavia F Aburjaile
- Universidade Federal de Pernambuco, Genetics Department, Center of Biosciences, Av. Prof. Moraes Rego, 1235, 50.670-423, Recife, Pernambuco, Brazil
| | - Tetsu Sakamoto
- Universidade Federal de Minas Gerais, Department of Biochemistry and Immunology, Belo Horizonte, Brazil
| | - Roberta L de Oliveira Silva
- Universidade Federal de Pernambuco, Genetics Department, Center of Biosciences, Av. Prof. Moraes Rego, 1235, 50.670-423, Recife, Pernambuco, Brazil
| | - Ederson A Kido
- Universidade Federal de Pernambuco, Genetics Department, Center of Biosciences, Av. Prof. Moraes Rego, 1235, 50.670-423, Recife, Pernambuco, Brazil
| | - Lidiane L Barbosa Amorim
- Universidade Federal de Pernambuco, Genetics Department, Center of Biosciences, Av. Prof. Moraes Rego, 1235, 50.670-423, Recife, Pernambuco, Brazil.,Instituto Federal de Educação, Ciência e Tecnologia do Piauí, Campus Oeiras, Avenida Projetada, s/n, 64.500-000, Oeiras, Piauí, Brazil
| | - José M Ortega
- Universidade Federal de Minas Gerais, Department of Biochemistry and Immunology, Belo Horizonte, Brazil
| | - Ana M Benko-Iseppon
- Universidade Federal de Pernambuco, Genetics Department, Center of Biosciences, Av. Prof. Moraes Rego, 1235, 50.670-423, Recife, Pernambuco, Brazil
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Yamada Y, Cassidy A, Schaap P. The transcription factor Spores Absent A is a PKA dependent inducer of Dictyostelium sporulation. Sci Rep 2018; 8:6643. [PMID: 29704004 PMCID: PMC5923282 DOI: 10.1038/s41598-018-24915-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 04/11/2018] [Indexed: 11/09/2022] Open
Abstract
Sporulation in Dictyostelium fruiting bodies evolved from amoebozoan encystation with both being induced by cAMP acting on PKA, but with downstream components still being unknown. Using tagged mutagenesis to find missing pathway components, we identified a sporeless mutant defective in a nuclear protein, SpaA. Expression of prespore genes was strongly reduced in spaA- cells, while expression of many spore stage genes was absent. Chromatin immunoprecipitation (ChIP) of a SpaA-YFP gene fusion showed that (pre)spore gene promoters bind directly to SpaA, identifying SpaA as a transcriptional regulator. SpaA dependent spore gene expression required PKA in vivo and was stimulated in vitro by the membrane-permeant PKA agonist 8Br-cAMP. The PKA agonist also promoted SpaA binding to (pre)spore promoters, placing SpaA downstream of PKA. Sequencing of SpaA-YFP ChIPed DNA fragments revealed that SpaA binds at least 117 (pre)spore promoters, including those of other transcription factors that activate some spore genes. These factors are not in turn required for spaA expression, identifying SpaA as the major trancriptional inducer of sporulation.
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Affiliation(s)
- Yoko Yamada
- School of Life Sciences, University of Dundee, Dundee, DD15EH, Angus, UK
| | - Andrew Cassidy
- Tayside Centre for Genomic Analysis, University of Dundee, Dundee, DD19SY, Angus, UK
| | - Pauline Schaap
- School of Life Sciences, University of Dundee, Dundee, DD15EH, Angus, UK.
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Ding M, Li J, Fan X, He F, Yu X, Chen L, Zou S, Liang Y, Yu J. Aquaporin1 regulates development, secondary metabolism and stress responses in Fusarium graminearum. Curr Genet 2018; 64:1057-1069. [PMID: 29502265 DOI: 10.1007/s00294-018-0818-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 02/13/2018] [Accepted: 02/27/2018] [Indexed: 12/20/2022]
Abstract
The Ascomycete fungus Fusarium graminearum, the causal agent of Fusarium head blight of wheat and barley, has become a predominant model organism for the study of fungal phytopathogens. Aquaporins (AQPs) have been implicated in the transport of water, glycerol, and a variety of other small molecules in yeast, plants and animals. However, the role of these proteins in phytopathogenic fungi is not well understood. Here, we identified and attempted to elucidate the function of the five aquaporin genes in F. graminearum. The phylogenetic analysis revealed that FgAQPs are divided into two clades, with FgAQP1 in the first clade. The ∆AQP1 mutant formed whitish colonies with longer aerial hyphae and reduced conidiation and perithecium formation. The ∆AQP1 mutant conidia were morphologically abnormal and appeared to undergo abnormal germination. The ∆AQP1 mutant and the wild type strain were equally pathogenic, while the mutant produced significantly higher quantities of deoxynivalenol (DON). The ∆AQP1 mutant also exhibited increased resistance to osmotic and oxidative stress as well as cell-wall perturbing agents. Using FgAQP1-GFP and DAPI staining, we found that FgAQP1 is localized to the nuclear membrane in conidia. Importantly, deletion of FgAQP1 increased the severity of conidium autophagy. Taken together, these results suggest that FgAQP1 is involved in hyphal development, stress responses, secondary metabolism, and sexual and asexual reproduction in F. graminearum. Unlike the ∆AQP1 mutant, the ∆AQP2, ∆AQP3, ∆AQP4 and ∆AQP5 mutants had no variable phenotypes.
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Affiliation(s)
- Mingyu Ding
- Key Laboratory of Agricultural Microbiology, College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China
| | - Jing Li
- Key Laboratory of Agricultural Microbiology, College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China
| | - Xinyue Fan
- Key Laboratory of Agricultural Microbiology, College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China
| | - Fang He
- Key Laboratory of Agricultural Microbiology, College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China
| | - Xiaoyang Yu
- Key Laboratory of Agricultural Microbiology, College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China
| | - Lei Chen
- Key Laboratory of Agricultural Microbiology, College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China
| | - Shenshen Zou
- Key Laboratory of Agricultural Microbiology, College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China
| | - Yuancun Liang
- Key Laboratory of Agricultural Microbiology, College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China.
| | - Jinfeng Yu
- Key Laboratory of Agricultural Microbiology, College of Plant Protection, Shandong Agricultural University, Tai'an, 271018, China
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The Roles of Aquaporins in Plant Stress Responses. J Dev Biol 2016; 4:jdb4010009. [PMID: 29615577 PMCID: PMC5831814 DOI: 10.3390/jdb4010009] [Citation(s) in RCA: 175] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 01/30/2016] [Accepted: 02/01/2016] [Indexed: 12/26/2022] Open
Abstract
Aquaporins are membrane channel proteins ubiquitously present in all kingdoms of life. Although aquaporins were originally discovered as water channels, their roles in the transport of small neutral solutes, gasses, and metal ions are now well established. Plants contain the largest number and greatest diversity of aquaporin homologs with diverse subcellular localization patterns, gating properties, and solute specificity. The roles of aquaporins in physiological functions throughout plant growth and development are well known. As an integral regulator of plant–water relations, they are presumed to play an important role in plant defense responses against biotic and abiotic stressors. This review highlights involvement of various aquaporin homologs in plant stress responses against a variety of environmental stresses that disturb plant cell osmotic balance and nutrient homeostasis.
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Von Bülow J, Beitz E. Number and regulation of protozoan aquaporins reflect environmental complexity. THE BIOLOGICAL BULLETIN 2015; 229:38-46. [PMID: 26338868 DOI: 10.1086/bblv229n1p38] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Protozoa are a diverse group of unicellular eukaryotes. Evidence has accumulated that protozoan aquaporin water and solute channels (AQP) contribute to adaptation in changing environments. Intracellular protozoan parasites live a well-sheltered life. Plasmodium spp. express a single AQP, Toxoplasma gondii two, while Trypanosoma cruzi and Leishamnia spp. encode up to five AQPs. Their AQPs are thought to import metabolic precursors and simultaneously to dispose of waste and to help parasites survive osmotic stress during transmission to and from the insect vector or during kidney passages. Trypanosoma brucei is a protozoan parasite that swims freely in the human blood. Expression and intracellular localization of the three T. brucei AQPs depend on the stage of differentiation during the life cycle, suggesting distinct roles in energy generation, metabolism, and cell motility. Free-living amoebae are in direct contact with the environment, encountering severe and sudden changes in the availability of nutrition, and in the osmotic conditions due to rainfall or drought. Amoeba proteus expresses a single AQP that is present in the contractile vacuole complex required for osmoregulation, whereas Dictyostelium discoideum expresses four AQPs, of which two are present in the single-celled amoeboidal stage and two more in the later multicellular stages preceding spore formation. The number and regulation of protozoan aquaporins may reflect environmental complexity. We highlight the gated AqpB from D. discoideum as an example of how life in the wild is challenged by a complex AQP structure-function relationship.
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Affiliation(s)
- Julia Von Bülow
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Gutenbergstrasse 76, 24118 Kiel, Germany
| | - Eric Beitz
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Gutenbergstrasse 76, 24118 Kiel, Germany
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von Bülow J, Golldack A, Albers T, Beitz E. The amoeboidalDictyosteliumaquaporin AqpB is gated via Tyr216 andaqpBgene deletion affects random cell motility. Biol Cell 2015; 107:78-88. [DOI: 10.1111/boc.201400070] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 12/22/2014] [Indexed: 02/03/2023]
Affiliation(s)
- Julia von Bülow
- Pharmaceutical and Medicinal Chemistry; Christian-Albrechts-University of Kiel; Kiel 24118 Germany
| | - André Golldack
- Pharmaceutical and Medicinal Chemistry; Christian-Albrechts-University of Kiel; Kiel 24118 Germany
| | - Tineke Albers
- Pharmaceutical and Medicinal Chemistry; Christian-Albrechts-University of Kiel; Kiel 24118 Germany
| | - Eric Beitz
- Pharmaceutical and Medicinal Chemistry; Christian-Albrechts-University of Kiel; Kiel 24118 Germany
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Aslam U, Khatoon A, Cheema HMN, Bashir A. Identification and characterization of plasma membrane aquaporins isolated from fiber cells of Calotropis procera. J Zhejiang Univ Sci B 2013; 14:586-95. [PMID: 23825144 PMCID: PMC3709063 DOI: 10.1631/jzus.b1200233] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 05/03/2013] [Indexed: 11/11/2022]
Abstract
Calotropis procera, commonly known as "milkweed", possesses long seed trichomes for seed dispersal and has the ability to survive under harsh conditions such as drought and salinity. Aquaporins are water channel proteins expressed in all land plants, divided into five subfamilies plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), NOD26-like proteins (NIPs), small basic intrinsic proteins (SIPs), and the unfamiliar X intrinsic proteins (XIPs). PIPs constitute the largest group of water channel proteins that are involved in different developmental and regulatory mechanisms including water permeability, cell elongation, and stomata opening. Aquaporins are also involved in abiotic stress tolerance and cell expansion mechanisms, but their role in seed trichomes (fiber cells) has never been investigated. A large number of clones isolated from C. procera fiber cDNA library showed sequence homology to PIPs. Both expressed sequence tags (ESTs) and real-time polymerase chain reaction (PCR) studies revealed that the transcript abundance of this gene family in fiber cells of C. procera is greater than that of cotton. Full-length cDNAs of CpPIP1 and CpPIP2 were isolated from C. procera fiber cDNA library and used for constructing plant expression vectors under constitutive (2×35S) and trichome-specific (GhLTP3) promoters. Transgenic tobacco plants were developed via Agrobacterium-mediated transformation. The phenotypic characteristics of the plants were observed after confirming the integration of transgene in plants. It was observed that CpPIP2 expression cassette under 2×35S and GhLTP3 promoter enhanced the numbers of stem and leave trichomes. However, 2×35S::CpPIP2 has a more amplified effect on trichome density and length than GhLTP3::CpPIP2 and other PIP constructs. These findings imply the role of C. procera PIP aquaporins in fiber cell elongation. The PIPs-derived cell expansion mechanism may be exploited through transgenic approaches for improvement of fiber staple length in cotton and boosting of defense against sucking insects by enhancing plant pubescence.
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Affiliation(s)
- Usman Aslam
- National Institute for Biotechnology and Genetic Engineering (NIBGE), P.O. Box 577, Jhang Road, Faisalabad 38000, Pakistan.
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von Bülow J, Müller-Lucks A, Kai L, Bernhard F, Beitz E. Functional characterization of a novel aquaporin from Dictyostelium discoideum amoebae implies a unique gating mechanism. J Biol Chem 2012; 287:7487-94. [PMID: 22262860 DOI: 10.1074/jbc.m111.329102] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The social amoeba Dictyostelium discoideum is a widely used model organism for studying basic functions of protozoan and metazoan cells, such as osmoregulation and cell motility. There is evidence from other species that cellular water channels, aquaporins (AQP), are central to both processes. Yet, data on D. discoideum AQPs is almost absent. Despite cloning of two putative D. discoideum AQPs, WacA, and AqpA, water permeability has not been shown. Further, WacA and AqpA are expressed at the late multicellular stage and in spores but not in amoebae. We cloned a novel AQP, AqpB, from amoeboidal D. discoideum cells. Wild-type AqpB was impermeable to water, glycerol, and urea when expressed in Xenopus laevis oocytes. Neither stepwise truncation of the N terminus nor selected point mutations activated the water channel. However, mutational truncation by 12 amino acids of an extraordinary long intracellular loop induced water permeability of AqpB, hinting at a novel gating mechanism. This AqpB mutant was inhibited by mercuric chloride, confirming the presence of a cysteine residue in the selectivity filter as predicted by our structure model. We detected AqpB by Western blot analysis in a glycosylated and a non-glycosylated form throughout all developmental stages. When expressed in D. discoideum amoebae, AqpB-GFP fusion constructs localized to vacuolar structures, to the plasma membrane, and to lamellipodia-like membrane protrusions. We conclude that the localization pattern in conjunction with channel gating may be indicative of AqpB functions in osmoregulation as well as cell motility of D. discoideum.
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Affiliation(s)
- Julia von Bülow
- Department of Medicinal and Pharmaceutical Chemistry, Christian-Albrechts-University of Kiel, 24118 Kiel, Germany
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Presence of aquaporin and V-ATPase on the contractile vacuole of Amoeba proteus. Biol Cell 2012; 100:179-88. [DOI: 10.1042/bc20070091] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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10
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Bae EK, Lee H, Lee JS, Noh EW. Drought, salt and wounding stress induce the expression of the plasma membrane intrinsic protein 1 gene in poplar (Populus alba×P. tremula var. glandulosa). Gene 2011; 483:43-8. [PMID: 21640804 DOI: 10.1016/j.gene.2011.05.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 05/17/2011] [Indexed: 10/18/2022]
Abstract
Water uptake across cell membranes is a principal requirement for plant growth at both the cellular and whole-plant levels; water movement through plant membranes is regulated by aquaporins (AQPs) or major intrinsic proteins (MIPs). We examined the expression characteristics of the poplar plasma membrane intrinsic protein 1 gene (PatPIP1), a type of MIP, which was isolated from a suspension cell cDNA library of Populus alba×P. tremula var. glandulosa. Examination of protoplasts expressing the p35S-PatPIP1::sGFP fusion protein revealed that the protein was localized in the plasma membrane. Northern blot analysis revealed that the gene was strongly expressed in poplar roots and leaves. Gene expression was inducible by abiotic factors including drought, salinity, cold temperatures and wounding, and also by plant hormones including gibberellic acid, jasmonic acid and salicylic acid. Since we found that the PatPIP1 gene was strongly expressed in response to mannitol, NaCl, jasmonic acid and wounding, we propose that PatPIP1 plays an essential role in the defense of plants against water stress.
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Affiliation(s)
- Eun-Kyung Bae
- Biotechnology Division, Korea Forest Research Institute, Suwon, Republic of Korea
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Benga G. Water channel proteins (later called aquaporins) and relatives: past, present, and future. IUBMB Life 2009; 61:112-33. [PMID: 19165894 DOI: 10.1002/iub.156] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Water channels or water channel proteins (WCPs) are transmembrane proteins that have a specific three-dimensional structure with a pore that can be permeated by water molecules. WCPs are large families (over 450 members) that are present in all kingdoms of life. The first WCP was discovered in the human red blood cell (RBC) membrane in 1980s. In 1990s other WCPs were discovered in plants, microorganisms, various animals, and humans; and it became obvious that the WCPs belong to the superfamily of major intrinsic proteins (MIPs, over 800 members). WCPs include three subfamilies: (a) aquaporins (AQPs), which are water specific (or selective water channels); (b) aquaglyceroporins (and glycerol facilitators), which are permeable to water and/or other small molecules; and (c) "superaquaporins" or subcellular AQPs. WCPs (and MIPs) have several structural characteristics which were better understood after the atomic structure of some MIPs was deciphered. The structure-function relationships of MIPs expressed in microorganisms (bacteria, archaea, yeast, and protozoa), plants, and some multicellular animal species [nematodes, insects, fishes, amphibians, mammals (and humans)] are described. A synthetic overview on the WCPs from RBCs from various species is provided. The physiological roles of WCPs in kidney, gastrointestinal system, respiratory apparatus, central nervous system, eye, adipose tissue, skin are described, and some implications of WCPs in various diseases are briefly presented. References of detailed reviews on each topic are given. This is the first review providing in a condensed form an overview of the whole WCP field that became in the last 20 years a very hot area of research in biochemistry and molecular cell biology, with wide and increasing implications.
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Affiliation(s)
- Gheorghe Benga
- Department of Cell and Molecular Biology, Iuliu HaTieganu University of Medicine and Pharmacy Cluj-Napoca, Cluj-Napoca, Romania.
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12
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Invertebrate aquaporins: a review. J Comp Physiol B 2008; 178:935-55. [DOI: 10.1007/s00360-008-0288-2] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 06/03/2008] [Accepted: 06/10/2008] [Indexed: 10/25/2022]
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Regulation of ammonia homeostasis by the ammonium transporter AmtA in Dictyostelium discoideum. EUKARYOTIC CELL 2007; 6:2419-28. [PMID: 17951519 DOI: 10.1128/ec.00204-07] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Ammonia has been shown to function as a morphogen at multiple steps during the development of the cellular slime mold Dictyostelium discoideum; however, it is largely unknown how intracellular ammonia levels are controlled. In the Dictyostelium genome, there are five genes that encode putative ammonium transporters: amtA, amtB, amtC, rhgA, and rhgB. Here, we show that AmtA regulates ammonia homeostasis during growth and development. We found that cells lacking amtA had increased levels of ammonia/ammonium, whereas their extracellular ammonia/ammonium levels were highly decreased. These results suggest that AmtA mediates the excretion of ammonium. In support of a role for AmtA in ammonia homeostasis, AmtA mRNA is expressed throughout the life cycle, and its expression level increases during development. Importantly, AmtA-mediated ammonia homeostasis is critical for many developmental processes. amtA(-) cells are more sensitive to NH(4)Cl than wild-type cells in inhibition of chemotaxis toward cyclic AMP and of formation of multicellular aggregates. Furthermore, even in the absence of exogenously added ammonia, we found that amtA(-) cells produced many small fruiting bodies and that the viability and germination of amtA(-) spores were dramatically compromised. Taken together, our data clearly demonstrate that AmtA regulates ammonia homeostasis and plays important roles in multiple developmental processes in Dictyostelium.
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Forrest KL, Bhave M. Major intrinsic proteins (MIPs) in plants: a complex gene family with major impacts on plant phenotype. Funct Integr Genomics 2007; 7:263-89. [PMID: 17562090 DOI: 10.1007/s10142-007-0049-4] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Revised: 03/06/2007] [Accepted: 03/27/2007] [Indexed: 10/23/2022]
Abstract
The ubiquitous cell membrane proteins called aquaporins are now firmly established as channel proteins that control the specific transport of water molecules across cell membranes in all living organisms. The aquaporins are thus likely to be of fundamental significance to all facets of plant growth and development affected by plant-water relations. A majority of plant aquaporins have been found to share essential structural features with the human aquaporin and exhibit water-transporting ability in various functional assays, and some have been shown experimentally to be of critical importance to plant survival. Furthermore, substantial evidence is now available from a number of plant species that shows differential gene expression of aquaporins in response to abiotic stresses such as salinity, drought, or cold and clearly establishes the aquaporins as major players in the response of plants to conditions that affect water availability. This review summarizes the function and regulation of these genes to develop a greater understanding of the response of plants to water insufficiency, and particularly, to identify tolerant genotypes of major crop species including wheat and rice and plants that are important in agroforestry.
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Affiliation(s)
- Kerrie L Forrest
- Environment and Biotechnology Centre, Faculty of Life and Social Sciences, Swinburne University of Technology, PO Box 218, John St, Hawthorn, Vic 3122, Australia
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Tanghe A, Van Dijck P, Thevelein JM. Why do microorganisms have aquaporins? Trends Microbiol 2006; 14:78-85. [PMID: 16406529 DOI: 10.1016/j.tim.2005.12.001] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2005] [Revised: 11/16/2005] [Accepted: 12/13/2005] [Indexed: 10/25/2022]
Abstract
Aquaporins are channel proteins that enhance the permeability of cell membranes for water. They have been found in Bacteria, Archaea and Eukaryotes. However, their absence in many microorganisms suggests that aquaporins do not fulfill a broad role such as turgor regulation or osmoadaptation but, instead, fulfill a role that enables microorganisms to have specific lifestyles. The recent discovery that aquaporins enhance cellular tolerance against rapid freezing suggests that they have ecological relevance. We have identified several examples of large-scale freeze-thawing of microbes in nature and we also draw attention to alternative lifestyle-related functions for aquaporins, which will be a focus of future research.
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Affiliation(s)
- An Tanghe
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, Katholieke Universiteit Leuven and Flanders Interuniversity Institute for Biotechnology (VIB), Kasteelpark Arenberg 31, B-3001 Leuven-Heverlee, Flanders, Belgium
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16
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Sidoux-Walter F, Pettersson N, Hohmann S. The Saccharomyces cerevisiae aquaporin Aqy1 is involved in sporulation. Proc Natl Acad Sci U S A 2004; 101:17422-7. [PMID: 15583134 PMCID: PMC536013 DOI: 10.1073/pnas.0404337101] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Aquaporins mediate rapid selective water transport across biological membranes. Elucidation of their precise physiological roles promises important insight into cellular and organismal osmoregulation. The genome of the yeast Saccharomyces cerevisiae encodes two similar but differentially regulated aquaporins. Here, we show that expression of AQY1 is stimulated during sporulation and that the Aqy1 protein is detectable exclusively in spore membranes. When spores are rapidly frozen, those that lack Aqy1 survive better, providing for a functional test of active spore water channels. Under ambient conditions, lack of Aqy1 reduces spore fitness. Because this reduction is independent from germination conditions, Aqy1 may be important during spore formation rather than subsequent maintenance or germination. Indeed, it seems that Aqy1 is degraded after spores have been formed and during germination. Taken together, Aqy1 is developmentally controlled and may play a role in spore maturation, probably by allowing water outflow. Taken together, we demonstrate a functional role of an aquaporin in gametogenesis, as well as in the formation of durable structures such as spores, a role that may have wider biological and medical implications.
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Affiliation(s)
- Frédéric Sidoux-Walter
- Department of Cell and Molecular Biology/Microbiology, Göteborg University, Box 462, S-40530 Göteborg, Sweden
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Hohmann S. Osmotic adaptation in yeast--control of the yeast osmolyte system. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 215:149-87. [PMID: 11952227 DOI: 10.1016/s0074-7696(02)15008-x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The yeast Saccharomyces cerevisiae (baker's yeast or budding yeast) is an excellent eukaryotic model system for cellular biology with a well-explored, completely sequenced genome. Yeast cells possess robust systems for osmotic adaptation. Central to the response to high osmolarity is the HOG pathway, one of the best-explored MAP kinase pathways. This pathway controls via different transcription factors the expression of more than 150 genes. In addition, osmotic responses are also controlled by protein kinase A via a general stress response pathway and by presently unknown signaling systems. The HOG pathway partially controls expression of genes encoding enzymes in glycerol production. Glycerol is the main yeast osmolyte, and its production is essential for growth in a high osmolarity medium. Upon hypo-osmotic shock, yeast cells transiently stimulate another MAP kinase pathway, the so-called PKC pathway, which appears to orchestrate the assembly of the cell surface and the cell wall. In addition, yeast cells show signs of a regulated volume decrease by rapidly exporting glycerol through Fps1p. This unusual MIP channel is gated by osmotic changes and thereby plays a key role in controlling the intracellular osmolyte content. Yeast cells also possess two aquaporins, Aqy1p and Aqy2p. The production of both proteins is strictly regulated, suggesting that these water channels play very specific roles in yeast physiology. Aqy1p appears to be developmentally regulated. Given the strong yeast research community and the excellent tools of genetics and functional genomics available, we expect yeast to be the best-explored cellular organism for several years ahead, and osmotic responses are a focus of interest for numerous yeast researchers.
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Affiliation(s)
- Stefan Hohmann
- Department of Cell and Molecular Biology, Göteborg University, Sweden
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