Highly regulated channels controlling plant water relations1 francois chaumont and stephen d. Aquaporins play a critical role in their daily lives so their cells can osmoregulate with the seawater or freshwater environments in which they swim. Thus, in this work, a genomewide analyses of sequence, structural. Aqps have remarkable features to provide an efficient and often, specific water flow and enable them to transport.
There are two routes for water to flow in these tissues, known as the. Msms analysis of peptides has previously shown to be a valuable tool to differentiate among pip homologues sharing a high sequence. Accumulating evidence indicates that aquaporins play a key role in plant water relations. Recent progress was made in understanding the molecular bases of aquaporin transport selectivity and gating. Plants appear to have a particularly large number of mip homologues. Pdf aquaporins are membrane channels that facilitate the transport. In plants, aquaporins occur as multiple isoforms reflecting a high diversity of cellular localizations and various physiological substrates in addition to water. Introduction to aquaporin structure in this unit you will use the conventional molecular graphics tools of vmd to become familiar with the key structural features of aquaporins, and how these are related to aquaporin function. Aquaporins and water permeability of plant membranes annual. From sequence to structure characterizing human and plant.
Structural mechanism of plant aquaporin gating nature. The aquaporins are a family of small 2430 kda poreforming integral membrane proteins. Sep 25, 20 aquaporins in the brain aqp4 is thought to be involved in brain swelling. Although information on aquaporins of some plants has been well documented, very little is known about aquaporins in cucumber.
Aquaporins aqps are protein channels that facilitate the transport of water andor small neutral solutes and gases. This is done by changing aquaporin density and activity in the membrane, including posttranslational modifications and. The regulatory role of aquaporins in cellular water transport and been demonstrated knepper, 1994. Aquaporins aqp are channel proteins belonging to the major intrinsic protein mip superfamily that play an important role in plant water. In plants, aquaporin aqp homologs, also called major intrinsic proteins mips, form a large protein family, with 35 identified members in arabidopsis johanson et al. Fifteen years after their discovery in plants, it now appears that studies on aquaporins have provided unique perspectives into multiple in tegrated aspects of plant biology. Aquaporins are intrinsic membrane proteins characterized by six transmembrane helices that selectively allow water. Identification of the family of aquaporin genes and their. So far aquaporins in plants were shown to be involved in root water uptake, reproduction or photosynthesis. Keywords gas transport, plantaquaporin, water channel. Excretory systems in flatworms, earthworms and vertebrates osmoregulation in bacteria, fish and protists osmoregulation in aquatic and terrestrial plants. The transgenic plants consume more water than wt plants, have a higher stomatal density in their young leaves, and exhibit a higher stomatal aperture induced by light. Exploring the roles of aquaporins in plantmicrobe interactions.
Plants counteract fluctuations in water supply by regulating all aquaporins in the cell plasma membrane. The mechanism by which water passes through biological membranes was a matter of debate until the discovery of the aquaporin water channels. Aquaporins are considered to be the main channels for the transport of water, as well as small neutral solutes and co 2, through the plant cell membrane tyerman et al. The fundamental importance of these proteins is suggested by their conservation from bacteria through plants to mammals. Based on sequence comparison, higher plant mips are divided into five subfamilies. Aquaporins aqp are channel proteins belonging to the major intrinsic protein mip superfamily that play an important role in plant water relations. King, masato yasui and peter agre the molecular basis of membrane waterpermeability remained elusive until the recent discovery of the aquaporin waterchannel proteins. Channels for the molecule of life extracellular side arr filter npa signature motifs intracellular side h4 he h3 h1 h5 h6 hb c n h2h figure 2 all aquaporin proteins share a common hourglass structure. When, later on, mip homologs were shown to function as water channels, the term aquaporin was suggested for. Plant growth and development are dependent on tight regulation of water movement.
Aquaporin 2 is regulated by vasopressin which, when bound to the cellsurface receptor, activates the camp signaling pathway. Fluorescence recovery after photobleaching reveals high. Aquaporins aqps are channelforming integral membrane proteins that facilitate the. Pdf water is the major component of all living cells, and efficient regulation of water homeostasis is essential for many biological processes. Mutation of the aquaporin 2 vasopressin receptor is a cause of acquired diabetes insipidus. Aquaporins are membrane proteins that belong to the major intrinsic protein mip family, with members found in nearly all living organisms agre et al. Aquaporins are small integral membrane proteins that belong to the ancient family of major intrinsic proteins mips, with members in animals, microbes, and plants. Identification and characterisation of aquaporins in wheat. But it is the astrocytes rather than epithelial cells that are involved. 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.
These channels are widely distributed in all kingdoms of life, including bacteria, plants, and mammals. Pdf the roles of aquaporins in plant stress responses. Aquaporins in the brain aqp4 is thought to be involved in brain swelling. Aquaporins as targets for stress tolerance in plants. The ability of certain plant aquaporins homologues to transport nutrient such as boron or gas such as co 2 has recently been demonstrated. Aquaporins and the control of the water status in coffee. Channel closure results either from the dephosphorylation of two conserved serine residues. The presence of aquaporins in the cell membranes seems to serve to facilitate the transcellular symplastic pathway for water transport. This ancient protein family was first named after its archetype, the major intrinsic protein mip of mammalian lens fibers 1, 2, which is now designated aqp0 see table 1. Gene expression and phylogenetic analysis of plant aquaporins. These data indicate that overexpression of this aqp gene, by enhancing the celltocell pathway of water movement within the leaf, might act as an internal factor to adapt the.
Plant aquaporin homologs can be classified according to their sequence into up to seven subfamilies 8, 9, which may also. This is done by changing aquaporin density and activity in the membrane, including posttranslational modifications and protein interaction that act on their. The use of highperformance liquid chromatography coupled to tandem mass spectrometry hplc. If aquaporins are gated channels, then they may open and close in response to variables, such as turgor pressure, in the cell. Water is the most important molecule in any kind of living cells. Plant aquaporins are localized in the plasma membrane, endoplasmic reticulum, vacuoles. 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. Because water is a major component of all living cells, including plants, our oxygen and food supply, the future study of aquaporins in plants is our future too. Aquaporins and plant water balance wiley online library. The complete genome of arabidopsisthaliana has 35 full. Aquaporins are membrane channel proteins that were initially identified and named based on their facilitating role in transmembrane water transport et al. Plant aquaporins, as channel proteins, are located in the plasma membrane and cytosolic regions, and play key regulatory roles in plant water.
The mechanisms of plant membrane water permeability have remained elusive until the recent discovery in both vacuolar and plasma membranes of a class of water channel proteins named aquaporins. Role of aquaporins in root water uptake annals of botany. Aqps have remarkable features to provide an efficient and often, specific water. In plants, aquaporins mediate a large part of the cell. In plants, aquaporins occur as multiple isoforms reflecting a high diversity of cellular localizations, transport selectivity, and regulation properties. This technique was used to discriminate between pm and endosomal pools of the aquaporin constructs, and to estimate their cycling between.
Highly efficient natureinspired membrane could potentially lower cost of water purification by 30 per cent. Aquaporins facilitate water transport across biomembranes in a manner dependent on osmotic pressure and waterpotential gradient. A major facilitator of water movement through cell membranes of cotton and other plants are the aquaporin proteins. Transcriptional regulation of aquaporins in accessions of. The high diversity of mips in plants during the last few years, the number of mzp genes reported in the data base steadily increased, and plant genes largely contributed to this inflow. Aquaporins are membrane water channels that play critical roles in controlling the water contents of cells. Fifteen years after their discovery in plants, it now appears that studies on aquaporins have provided unique perspectives into multiple integrated aspects of plant biology. Aquaporins in plants and animals are highly conserved and form large protein families with 35 members in higher plants 6 and members in humans 3,4,7. Accordingly, plant aquaporin classification as simple water pores has changed corresponding to their molecular function into channels permeable for water, small solutes andor gases. Plant aquaporins are part of a large and highly divergent protein family that can be divided into four subfamilies according to amino acid sequence similarity. As in other organisms, plant aquaporins facilitate the transcellular movement of water. Identification and characterisation of aquaporins in plants is no more than 100,000 words in length, exclusive of tables, figures, appendices, references and footnotes. The presence of aquaporins in the cell membranes seems to serve to facilitate the transcellular. Sep 01, 2002 aquaporins are membrane proteins that belong to the major intrinsic protein mip family, with members found in nearly all living organisms agre et al.
As a multigene family, plant aquaporins function not only in water transport but also in transport of small elements that are important for vegetative and reproductive growth of plants. Introduction the major plant biological processes including plant growth and development are dependent on. Aquaporins of higher plants exhibit a high diversity with 35, 36, 33 isoforms in arabidopsis, maize and rice, respectively. Aquaporins are membrane proteins that selectively conduct water molecules in and out.
Plant aquaporins, gene expression, npa motifs, phylogenetic, amino acid substitution. Aquaporin proteins are present as diverse forms in plants, where they function as transport systems for water and other small molecules. Plant aquaporin homologs can be classified according to their sequence into up to seven subfamilies 8, 9, which may also correspond to distinct subcellular localizations. In plants water is taken up from the soil through the roots, where it passes from the cortex into the vascular tissues. This results in aquaporin2 containing vesicles to increase water uptake and return to circulation. Analysis of root plasma membrane aquaporins from brassica. Transgenic arabidopsis plants that express gfp fusions with atpip1. Co 2 permeability as demonstrated for distinct aquaporins implies a function in one of the most important metabolic process in plants, the photosynthesis.
The discovery of aquaporins has facilitated research on intracellular and wholeplant water transport at the molecular level. Similar to their animal counterparts, plant aquaporins have six membranespanning domains and belong to the mip superfamily of transmembrane channel proteins. The molecular basis of plant aqua porin selectivity has been investigated more. Subsequent work has identified a wide variety of aquaporins, which can increase membrane permeability to specific small molecules such as urea ch 4 n 2 o. Higher plant aquaporins tonoplast intrinsic proteins the plant vacuole is a cellular storage compartment. Moshelion m, halperin o, wallach r et al 2015 role of aquaporins in determining transpiration and photosynthesis in waterstressed plants. Aquaporins belong to a ubiquitous family of membrane intrinsic proteins mip. Channels for the molecule of life uwe g hacke, university of alberta, edmonton, canada joan laur, university of alberta, edmonton, canada advanced article article contents introduction a discovery well worth a nobel prize structure, permeation and substrate speci.
Literature cited agre p, am saboori, a asimos, bl smith. Photosynthetic efficiency and mesophyll conductance are. Plants have the capacity to regulate aquaporin activity. Stably transformed arabidopsis plants expressing atpip1.
Aquaporins are membrane channels that facilitate the transport of water and small neutral molecules across biological membranes of most living organisms. Msms analysis of peptides has previously shown to be a valuable tool to differentiate among pip homologues. Pdf aquaporins are membrane channels that facilitate the transport of water and small neutral molecules across biological membranes of most living. Use one of the following example to help illustrate you explanation. Structure and function of aquaporins you will first consider bovine aquaporin pdb code 1j4n. Aquaporins include seven subfamilies categorized according to their intracellular locations and sequence similarities. The plant aquaporins belong to the large major intrinsic protein mip family. Plant aquaporins are localized in the plasma membrane, endoplasmic reticulum, vacuoles, plastids and, in some species, in membrane compartments interacting with symbiotic organisms.
This book will summarize the recent advances regarding plant aquaporins, their phylogeny, structure, substrate specificity, mechanisms of regulation and roles in various important physiological processes related to the control of water flow and small solute distribution at the cell, tissue and plant level in an everchanging environment. Aquaporins and the control of the water status in coffee plants. Regulation of aquaporins in plants under stress springerlink. Aquaporins are channel proteins present in the plasma and intracellular membranes of plant cells, where they facilitate the transport of water andor small neutral solutes urea, boric acid, silicic acid or gases ammonia, carbon dioxide. Water is the major component of all living cells, and efficient regulation of water homeostasis is essential for many biological processes. Regulation of aquaporins in plants under stress biological. Genomewide identification, structure characterization. Given the potential value of aquaporins in improving stress tolerance, it is necessary to identify aquaporin genes in cucumber. The ubiquitous and highly regulated expression of aquaporins in plants also suggests that transmembrane water transport may be relevant to many processes other than those related to transpiration.
Aquaporins are membrane channel proteins ubiquitously present in all kingdoms of life. The main role of aquaporins in plants is transport of water and other small neutral molecules across cellular biological membranes. The aquaporins are small, very hydrophobic, intrinsic membrane proteins. This thesis contains no material that has been submitted previously, in whole or in part, for the award of any other academic degree or.
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