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Zhou LH, Weizbauer RA, Singamaneni S, Xu F, Genin GM, Pickard BG. Structures formed by a cell membrane-associated arabinogalactan-protein on graphite or mica alone and with Yariv phenylglycosides. ANNALS OF BOTANY 2014; 114:1385-97. [PMID: 25164699 PMCID: PMC4195565 DOI: 10.1093/aob/mcu172] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 07/03/2014] [Indexed: 05/10/2023]
Abstract
BACKGROUND Certain membrane-associated arabinogalactan-proteins (AGPs) with lysine-rich sub-domains participate in plant growth, development and resistance to stress. To complement fluorescence imaging of such molecules when tagged and introduced transgenically to the cell periphery and to extend the groundwork for assessing molecular structure, some behaviours of surface-spread AGPs were visualized at the nanometre scale in a simplified electrostatic environment. METHODS Enhanced green fluorescent protein (EGFP)-labelled LeAGP1 was isolated from Arabidopsis thaliana leaves using antibody-coated magnetic beads, deposited on graphite or mica, and examined with atomic force microscopy (AFM). KEY RESULTS When deposited at low concentration on graphite, LeAGP can form independent clusters and rings a few nanometres in diameter, often defining deep pits; the aperture of the rings depends on plating parameters. On mica, intermediate and high concentrations, respectively, yielded lacy meshes and solid sheets that could dynamically evolve arcs, rings, 'pores' and 'co-pores', and pits. Glucosyl Yariv reagent combined with the AGP to make very large and distinctive rings. CONCLUSIONS Diverse cell-specific nano-patterns of native lysine-rich AGPs are expected at the wall-membrane interface and, while there will not be an identical patterning in different environmental settings, AFM imaging suggests protein tendencies for surficial organization and thus opens new avenues for experimentation. Nanopore formation with Yariv reagents suggests how the reagent might bind with AGP to admit Ca(2+) to cells and hints at ways in which AGP might be structured at some cell surfaces.
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Affiliation(s)
- Li Hong Zhou
- Gladys Levis Allen Laboratory of Plant Sensory Physiology, Biology Department, Washington University in St. Louis, St. Louis, MO, USA Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, USA Biomedical Engineering & Biomechanics Center, Xi'an Jiaotong University, Xi'an, China
| | - Renate A Weizbauer
- Gladys Levis Allen Laboratory of Plant Sensory Physiology, Biology Department, Washington University in St. Louis, St. Louis, MO, USA Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, USA Carnegie Institution, Department of Plant Biology, Stanford, CA, USA
| | - Srikanth Singamaneni
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, USA
| | - Feng Xu
- Biomedical Engineering & Biomechanics Center, Xi'an Jiaotong University, Xi'an, China School of Life Science & Technology, Xi'an Jiaotong University, Xi'an, China
| | - Guy M Genin
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, USA
| | - Barbara G Pickard
- Gladys Levis Allen Laboratory of Plant Sensory Physiology, Biology Department, Washington University in St. Louis, St. Louis, MO, USA
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102
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Lamport DTA, Varnai P, Seal CE. Back to the future with the AGP-Ca2+ flux capacitor. ANNALS OF BOTANY 2014; 114:1069-85. [PMID: 25139429 PMCID: PMC4195563 DOI: 10.1093/aob/mcu161] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 06/17/2014] [Indexed: 05/18/2023]
Abstract
BACKGROUND Arabinogalactan proteins (AGPs) are ubiquitous in green plants. AGPs comprise a widely varied group of hydroxyproline (Hyp)-rich cell surface glycoproteins (HRGPs). However, the more narrowly defined classical AGPs massively predominate and cover the plasma membrane. Extensive glycosylation by pendant polysaccharides O-linked to numerous Hyp residues like beads of a necklace creates a unique ionic compartment essential to a wide range of physiological processes including germination, cell extension and fertilization. The vital clue to a precise molecular function remained elusive until the recent isolation of small Hyp-arabinogalactan polysaccharide subunits; their structural elucidation by nuclear magentic resonance imaging, molecular simulations and direct experiment identified a 15-residue consensus subunit as a β-1,3-linked galactose trisaccharide with two short branched sidechains each with a single glucuronic acid residue that binds Ca(2+) when paired with its adjacent sidechain. SCOPE AGPs bind Ca(2+) (Kd ∼ 6 μm) at the plasma membrane (PM) at pH ∼5·5 but release it when auxin-dependent PM H(+)-ATPase generates a low periplasmic pH that dissociates AGP-Ca(2+) carboxylates (pka ∼3); the consequential large increase in free Ca(2+) drives entry into the cytosol via Ca(2+) channels that may be voltage gated. AGPs are thus arguably the primary source of cytosolic oscillatory Ca(2+) waves. This differs markedly from animals, in which cytosolic Ca(2+) originates mostly from internal stores such as the sarcoplasmic reticulum. In contrast, we propose that external dynamic Ca(2+) storage by a periplasmic AGP capacitor co-ordinates plant growth, typically involving exocytosis of AGPs and recycled Ca(2+), hence an AGP-Ca(2+) oscillator. CONCLUSIONS The novel concept of dynamic Ca(2+) recycling by an AGP-Ca(2+) oscillator solves the long-standing problem of a molecular-level function for classical AGPs and thus integrates three fields: AGPs, Ca(2+) signalling and auxin. This accounts for the involvement of AGPs in plant morphogenesis, including tropic and nastic movements.
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Affiliation(s)
- Derek T A Lamport
- School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK
| | - Peter Varnai
- School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK
| | - Charlotte E Seal
- Seed Conservation Department, Royal Botanic Gardens, Kew, Wakehurst Place, Ardingly, West Sussex RH17 6TN, UK
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103
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Pereira AM, Masiero S, Nobre MS, Costa ML, Solís MT, Testillano PS, Sprunck S, Coimbra S. Differential expression patterns of arabinogalactan proteins in Arabidopsis thaliana reproductive tissues. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:5459-71. [PMID: 25053647 PMCID: PMC4400541 DOI: 10.1093/jxb/eru300] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 06/12/2014] [Accepted: 06/15/2014] [Indexed: 05/05/2023]
Abstract
Arabinogalactan proteins (AGPs) are heavily glycosylated proteins existing in all members of the plant kingdom and are differentially distributed through distinctive developmental stages. Here, we showed the individual distributions of specific Arabidopsis AGPs: AGP1, AGP9, AGP12, AGP15, and AGP23, throughout reproductive tissues and indicated their possible roles in several reproductive processes. AGP genes specifically expressed in female tissues were identified using available microarray data. This selection was confirmed by promoter analysis using multiple green fluorescent protein fusions to a nuclear localization signal, β-glucuronidase fusions, and in situ hybridization as approaches to confirm the expression patterns of the AGPs. Promoter analysis allowed the detection of a specific and differential presence of these proteins along the pathway followed by the pollen tube during its journey to reach the egg and the central cell inside the embryo sac. AGP1 was expressed in the stigma, style, transmitting tract, and the chalazal and funiculus tissues of the ovules. AGP9 was present along the vasculature of the reproductive tissues and AGP12 was expressed in the stigmatic cells, chalazal and funiculus cells of the ovules, and in the septum. AGP15 was expressed in all pistil tissues, except in the transmitting tract, while AGP23 was specific to the pollen grain and pollen tube. The expression pattern of these AGPs provides new evidence for the detection of a subset of specific AGPs involved in plant reproductive processes, being of significance for this field of study. AGPs are prominent candidates for male-female communication during reproduction.
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Affiliation(s)
- Ana Marta Pereira
- Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal Center for Biodiversity, Functional & Integrative Genomics (BioFIG), Porto, Portugal Dipartimento di BioScienze, Università degli Studi di Milano, 20133 Milan, Italy
| | - Simona Masiero
- Dipartimento di BioScienze, Università degli Studi di Milano, 20133 Milan, Italy
| | - Margarida Sofia Nobre
- Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
| | - Mário Luís Costa
- Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal Center for Biodiversity, Functional & Integrative Genomics (BioFIG), Porto, Portugal
| | - María-Teresa Solís
- Pollen Biotechnology of Crop Plants Group, Centro de Investigaciones Biológicas (CIB) CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Pilar S Testillano
- Pollen Biotechnology of Crop Plants Group, Centro de Investigaciones Biológicas (CIB) CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Stefanie Sprunck
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany
| | - Sílvia Coimbra
- Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal Center for Biodiversity, Functional & Integrative Genomics (BioFIG), Porto, Portugal
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104
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Hijazi M, Velasquez SM, Jamet E, Estevez JM, Albenne C. An update on post-translational modifications of hydroxyproline-rich glycoproteins: toward a model highlighting their contribution to plant cell wall architecture. FRONTIERS IN PLANT SCIENCE 2014; 5:395. [PMID: 25177325 PMCID: PMC4132260 DOI: 10.3389/fpls.2014.00395] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 07/24/2014] [Indexed: 05/04/2023]
Abstract
Plant cell walls are composite structures mainly composed of polysaccharides, also containing a large set of proteins involved in diverse functions such as growth, environmental sensing, signaling, and defense. Research on cell wall proteins (CWPs) is a challenging field since present knowledge of their role into the structure and function of cell walls is very incomplete. Among CWPs, hydroxyproline (Hyp)-rich O-glycoproteins (HRGPs) were classified into three categories: (i) moderately glycosylated extensins (EXTs) able to form covalent scaffolds; (ii) hyperglycosylated arabinogalactan proteins (AGPs); and (iii) Hyp/proline (Pro)-Rich proteins (H/PRPs) that may be non-, weakly- or highly-glycosylated. In this review, we provide a description of the main features of their post-translational modifications (PTMs), biosynthesis, structure, and function. We propose a new model integrating HRGPs and their partners in cell walls. Altogether, they could form a continuous glyco-network with non-cellulosic polysaccharides via covalent bonds or non-covalent interactions, thus strongly contributing to cell wall architecture.
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Affiliation(s)
- May Hijazi
- Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, UPS, UMR 5546Castanet-Tolosan, France
- CNRS, UMR 5546Castanet-Tolosan, France
| | - Silvia M. Velasquez
- Facultad de Ciencias Exactas y Naturales, Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE-CONICET), Universidad de Buenos AiresBuenos Aires, Argentina
| | - Elisabeth Jamet
- Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, UPS, UMR 5546Castanet-Tolosan, France
- CNRS, UMR 5546Castanet-Tolosan, France
| | - José M. Estevez
- Facultad de Ciencias Exactas y Naturales, Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE-CONICET), Universidad de Buenos AiresBuenos Aires, Argentina
| | - Cécile Albenne
- Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, UPS, UMR 5546Castanet-Tolosan, France
- CNRS, UMR 5546Castanet-Tolosan, France
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105
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Paulsen B, Craik D, Dunstan D, Stone B, Bacic A. The Yariv reagent: Behaviour in different solvents and interaction with a gum arabic arabinogalactanprotein. Carbohydr Polym 2014; 106:460-8. [DOI: 10.1016/j.carbpol.2014.01.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 12/06/2013] [Accepted: 01/03/2014] [Indexed: 10/25/2022]
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106
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Tryfona T, Theys TE, Wagner T, Stott K, Keegstra K, Dupree P. Characterisation of FUT4 and FUT6 α-(1 → 2)-fucosyltransferases reveals that absence of root arabinogalactan fucosylation increases Arabidopsis root growth salt sensitivity. PLoS One 2014; 9:e93291. [PMID: 24667545 PMCID: PMC3965541 DOI: 10.1371/journal.pone.0093291] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 03/04/2014] [Indexed: 11/22/2022] Open
Abstract
Plant type II arabinogalactan (AG) polysaccharides are attached to arabinogalactan proteins (AGPs) at hydroxyproline residues, and they are very diverse and heterogeneous structures. The AG consists of a β-(1→3)-linked galactan backbone with β-(1→6)-galactan side chains that are modified mainly with arabinose, but they may also contain glucuronic acid, rhamnose or other sugars. Here, we studied the positions of fucose substitutions in AGPs, and we investigated the functions of this fucosylation. Monosaccharide analysis of Arabidopsis leaf AGP extracts revealed a significant reduction in L-Fucose content in the fut4 mutant, but not in the fut6 mutant. In addition, Fucose was reduced in the fut4 mutant in root AGP extracts and was absent in the fut4/fut6 mutant. Curiously, in all cases reduction of fucose was accompanied with a reduction in xylose levels. The fucosylated AGP structures in leaves and roots in wild type and fut mutant plants were characterised by sequential digestion with AG specific enzymes, analysis by Polysaccharide Analysis using Carbohydrate gel Electrophoresis, and Matrix Assisted Laser Desorption/Ionisation (MALDI)-Time of Flight Mass spectrometry (MS). We found that FUT4 is solely responsible for the fucosylation of AGPs in leaves. The Arabidopsis thaliana FUT4 and FUT6 genes have been previously proposed to be non-redundant AG-specific fucosyltransferases. Unexpectedly, FUT4 and FUT6 enzymes both fucosylate the same AGP structures in roots, suggesting partial redundancy to each other. Detailed structural characterisation of root AGPs with high energy MALDI-Collision Induced Dissociation MS and NMR revealed an abundant unique AG oligosaccharide structure consisting of terminal xylose attached to fucose. The loss of this structure in fut4/fut6 mutants explains the reduction of both fucose and xylose in AGP extracts. Under salt-stress growth conditions the fut4/fut6 mutant lacking AGP fucosylation exhibited a shorter root phenotype than wild type plants, implicating fucosylation of AGPs in maintaining proper cell expansion under these conditions.
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Affiliation(s)
- Theodora Tryfona
- School of Biological Sciences, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Tina E. Theys
- School of Biological Sciences, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Tanya Wagner
- DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, United States of America
| | - Katherine Stott
- School of Biological Sciences, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Kenneth Keegstra
- DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, United States of America
| | - Paul Dupree
- School of Biological Sciences, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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107
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Knoch E, Dilokpimol A, Geshi N. Arabinogalactan proteins: focus on carbohydrate active enzymes. FRONTIERS IN PLANT SCIENCE 2014; 5:198. [PMID: 24966860 PMCID: PMC4052742 DOI: 10.3389/fpls.2014.00198] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 04/24/2014] [Indexed: 05/02/2023]
Abstract
Arabinogalactan proteins (AGPs) are a highly diverse class of cell surface proteoglycans that are commonly found in most plant species. AGPs play important roles in many cellular processes during plant development, such as reproduction, cell proliferation, pattern formation and growth, and in plant-microbe interaction. However, little is known about the molecular mechanisms of their function. Numerous studies using monoclonal antibodies that recognize different AGP glycan epitopes have shown the appearance of a slightly altered AGP glycan in a specific stage of development in plant cells. Therefore, it is anticipated that the biosynthesis and degradation of AGP glycan is tightly regulated during development. Until recently, however, little was known about the enzymes involved in the metabolism of AGP glycans. In this review, we summarize recent discoveries of carbohydrate active enzymes (CAZy; http://www.cazy.org/) involved in the biosynthesis and degradation of AGP glycans, and we discuss the biological role of these enzymes in plant development.
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Affiliation(s)
| | | | - Naomi Geshi
- *Correspondence: Naomi Geshi, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Copenhagen, Denmark e-mail:
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108
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Zou YF, Zhang BZ, Inngjerdingen KT, Barsett H, Diallo D, Michaelsen TE, El-zoubair E, Paulsen BS. Polysaccharides with immunomodulating properties from the bark of Parkia biglobosa. Carbohydr Polym 2014; 101:457-63. [DOI: 10.1016/j.carbpol.2013.09.082] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 08/08/2013] [Accepted: 09/21/2013] [Indexed: 11/30/2022]
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109
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Endo M, Kotake T, Watanabe Y, Kimura K, Tsumuraya Y. Biosynthesis of the carbohydrate moieties of arabinogalactan proteins by membrane-bound β-glucuronosyltransferases from radish primary roots. PLANTA 2013; 238:1157-1169. [PMID: 24057431 PMCID: PMC3898515 DOI: 10.1007/s00425-013-1959-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 09/09/2013] [Indexed: 05/29/2023]
Abstract
A membrane fraction from etiolated 6-day-old primary radish roots (Raphanus sativus L. var hortensis) contained β-glucuronosyltransferases (GlcATs) involved in the synthesis of the carbohydrate moieties of arabinogalactan proteins (AGPs). The GlcATs transferred [(14)C]GlcA from UDP-[(14)C]GlcA on to β-(1 → 3)-galactan as an exogenous acceptor substrate, giving a specific activity of 50-150 pmol min(-1) (mg protein)(-1). The enzyme specimen also catalyzed the transfer of [(14)C]GlcA on to an enzymatically modified AGP from mature radish root. Analysis of the transfer products revealed that the transfer of [(14)C]GlcA occurred preferentially on to consecutive (1 → 3)-linked β-Gal chains as well as single branched β-(1 → 6)-Gal residues through β-(1 → 6) linkages, producing branched acidic side chains. The enzymes also transferred [(14)C]GlcA residues on to several oligosaccharides, such as β-(1 → 6)- and β-(1 → 3)-galactotrioses. A trisaccharide, α-L-Araf-(1 → 3)-β-Gal-(1 → 6)-Gal, was a good acceptor, yielding a branched tetrasaccharide, α-L-Araf-(1 → 3)[β-GlcA-(1 → 6)]-β-Gal-(1 → 6)-Gal. We report the first in vitro assay system for β-GlcATs involved in the AG synthesis as a step toward full characterization and cloning.
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Affiliation(s)
- Maya Endo
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan
| | - Toshihisa Kotake
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan
| | - Yoko Watanabe
- Yakult Central Institute for Microbiological Research, 1796 Yaho, Kunitachi, Tokyo, 186-8650, Japan
| | - Kazumasa Kimura
- Yakult Central Institute for Microbiological Research, 1796 Yaho, Kunitachi, Tokyo, 186-8650, Japan
| | - Yoichi Tsumuraya
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan.
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110
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Knoch E, Dilokpimol A, Tryfona T, Poulsen CP, Xiong G, Harholt J, Petersen BL, Ulvskov P, Hadi MZ, Kotake T, Tsumuraya Y, Pauly M, Dupree P, Geshi N. A β-glucuronosyltransferase from Arabidopsis thaliana involved in biosynthesis of type II arabinogalactan has a role in cell elongation during seedling growth. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 76:1016-29. [PMID: 24128328 DOI: 10.1111/tpj.12353] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 09/30/2013] [Accepted: 10/08/2013] [Indexed: 05/18/2023]
Abstract
We have characterized a β-glucuronosyltransferase (AtGlcAT14A) from Arabidopsis thaliana that is involved in the biosynthesis of type II arabinogalactan (AG). This enzyme belongs to the Carbohydrate Active Enzyme database glycosyltransferase family 14 (GT14). The protein was localized to the Golgi apparatus when transiently expressed in Nicotiana benthamiana. The soluble catalytic domain expressed in Pichia pastoris transferred glucuronic acid (GlcA) to β-1,6-galactooligosaccharides with degrees of polymerization (DP) ranging from 3-11, and to β-1,3-galactooligosaccharides of DP5 and 7, indicating that the enzyme is a glucuronosyltransferase that modifies both the β-1,6- and β-1,3-galactan present in type II AG. Two allelic T-DNA insertion mutant lines showed 20-35% enhanced cell elongation during seedling growth compared to wild-type. Analyses of AG isolated from the mutants revealed a reduction of GlcA substitution on Gal-β-1,6-Gal and β-1,3-Gal, indicating an in vivo role of AtGlcAT14A in synthesis of those structures in type II AG. Moreover, a relative increase in the levels of 3-, 6- and 3,6-linked galactose (Gal) and reduced levels of 3-, 2- and 2,5-linked arabinose (Ara) were seen, suggesting that the mutation in AtGlcAT14A results in a relative increase of the longer and branched β-1,3- and β-1,6-galactans. This increase of galactosylation in the mutants is most likely caused by increased availability of the O6 position of Gal, which is a shared acceptor site for AtGlcAT14A and galactosyltransferases in synthesis of type II AG, and thus addition of GlcA may terminate Gal chain extension. We discuss a role for the glucuronosyltransferase in the biosynthesis of type II AG, with a biological role during seedling growth.
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Affiliation(s)
- Eva Knoch
- Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, 1871, Denmark
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111
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Geshi N, Johansen JN, Dilokpimol A, Rolland A, Belcram K, Verger S, Kotake T, Tsumuraya Y, Kaneko S, Tryfona T, Dupree P, Scheller HV, Höfte H, Mouille G. A galactosyltransferase acting on arabinogalactan protein glycans is essential for embryo development in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 76:128-37. [PMID: 23837821 DOI: 10.1111/tpj.12281] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 05/31/2013] [Accepted: 06/24/2013] [Indexed: 05/18/2023]
Abstract
Arabinogalactan proteins (AGPs) are a complex family of cell-wall proteoglycans that are thought to play major roles in plant growth and development. Genetic approaches to studying AGP function have met limited success so far, presumably due to redundancy within the large gene families encoding AGP backbones. Here we used an alternative approach for genetic dissection of the role of AGPs in development by modifying their glycan side chains. We have identified an Arabidopsis glycosyltransferase of CAZY family GT31 (AtGALT31A) that galactosylates AGP side chains. A mutation in the AtGALT31A gene caused the arrest of embryo development at the globular stage. The presence of the transcript in the suspensor of globular-stage embryos is consistent with a role for AtGALT31A in progression of embryo development beyond the globular stage. The first observable defect in the mutant is perturbation of the formative asymmetric division of the hypophysis, indicating an essential role for AGP proteoglycans in either specification of the hypophysis or orientation of the asymmetric division plane.
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Affiliation(s)
- Naomi Geshi
- Department of Plant Biology and Biotechnology, University of Copenhagen, Thorvaldsensvej 40, Copenhagen, Frederiksberg C, 1871, Denmark
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112
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Tseng IC, Hong CY, Yu SM, Ho THD. Abscisic acid- and stress-induced highly proline-rich glycoproteins regulate root growth in rice. PLANT PHYSIOLOGY 2013; 163:118-34. [PMID: 23886623 PMCID: PMC3762635 DOI: 10.1104/pp.113.217547] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
In the root of rice (Oryza sativa), abscisic acid (ABA) treatment, salinity, or water deficit stress induces the expression of a family of four genes, REPETITIVE PROLINE-RICH PROTEIN (RePRP). These genes encode two subclasses of novel proline-rich glycoproteins with highly repetitive PX₁PX₂ motifs, RePRP1 and RePRP2. RePRP orthologs exist only in monocotyledonous plants, and their functions are virtually unknown. Rice RePRPs are heavily glycosylated with arabinose and glucose on multiple hydroxyproline residues. They are significantly different from arabinogalactan proteins that have glycan chains composed of arabinose and galactose. Transient and stable expressions of RePRP-green fluorescent protein reveal that a fraction of this protein is localized to the plasma membrane. In rice roots, ABA treatment increases RePRP expression preferentially in the elongation zone. Overexpression of RePRP in transgenic rice reduces root cell elongation in the absence of ABA, similar to the effect of ABA on wild-type roots. Conversely, simultaneous knockdown of the expression of RePRP1 and RePRP2 reduces the root sensitivity to ABA, indicating that RePRP proteins play an essential role in ABA/stress regulation of root growth and development. Moreover, rice RePRPs specifically interact with a polysaccharide, arabinogalactan, in a dosage-dependent manner. It is suggested that RePRP1 and RePRP2 are functionally redundant suppressors of root cell expansion and probably act through interactions with cell wall components near the plasma membrane.
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113
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Nguema-Ona E, Vicré-Gibouin M, Cannesan MA, Driouich A. Arabinogalactan proteins in root-microbe interactions. TRENDS IN PLANT SCIENCE 2013; 18:440-9. [PMID: 23623239 DOI: 10.1016/j.tplants.2013.03.006] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 03/18/2013] [Accepted: 03/28/2013] [Indexed: 05/20/2023]
Abstract
Arabinogalactan proteins (AGPs) are among the most intriguing sets of macromolecules, specific to plants, structurally complex, and found abundantly in all plant organs including roots, as well as in root exudates. AGPs have been implicated in several fundamental plant processes such as development and reproduction. Recently, they have emerged as interesting actors of root-microbe interactions in the rhizosphere. Indeed, recent findings indicate that AGPs play key roles at various levels of interaction between roots and soil-borne microbes, either beneficial or pathogenic. Therefore, the focus of this review is the role of AGPs in the interactions between root cells and microbes. Understanding this facet of AGP function will undoubtedly improve plant health and crop protection.
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Affiliation(s)
- Eric Nguema-Ona
- Laboratoire Glycobiologie et Matrice Extracellulaire Végétale (Glyco-MEV)-EA 4358, Plate-forme d'Imagerie Cellulaire (PRIMACEN) et Grand Réseau de Recherche VASI de Haute Normandie, PRES Normandie Université, Université de Rouen, 76821 Mont Saint Aignan, Cedex, France
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114
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Driouich A, Follet-Gueye ML, Vicré-Gibouin M, Hawes M. Root border cells and secretions as critical elements in plant host defense. CURRENT OPINION IN PLANT BIOLOGY 2013; 16:489-95. [PMID: 23856080 DOI: 10.1016/j.pbi.2013.06.010] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 06/11/2013] [Accepted: 06/13/2013] [Indexed: 05/20/2023]
Abstract
Border cells and border-like cells are released from the root tip as individual cells and small aggregates, or as a group of attached cells. These are viable components of the root system that play a key role in controlling root interaction with living microbes of the rhizosphere. As their separation from root tip proceeds, the cells synthesize and secrete a hydrated mucilage that contains polysaccharides, secondary metabolites, antimicrobial proteins and extracellular DNA (exDNA). This exDNA-based matrix seems to function in root defense in a way similar to that of recently characterized neutrophil extracellular traps (NETs) in mammalian cells. This review discusses the role of the cells and secreted compounds in the protection of root tip against microbial infections.
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Affiliation(s)
- Azeddine Driouich
- Laboratoire Glycobiologie et Matrice Extracellulaire Végétale (EA 4358), Grand Réseau de Recherche VASI Végétal-Agronomie-Sols et Innovations et Plate Forme d'Imagerie Cellulaire (PRIMACEN) de Haute Normandie, Université de Rouen, 76821 Mont Saint Aignan Cedex, France.
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115
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Misra BB, Dey S. Culture of East Indian sandalwood tree somatic embryos in air-lift bioreactors for production of santalols, phenolics and arabinogalactan proteins. AOB PLANTS 2013; 5:plt025. [PMCID: PMC4455360 DOI: 10.1093/aobpla/plt025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Accepted: 04/29/2013] [Indexed: 05/30/2023]
Abstract
The Indian Sandalwood tree is globally acclaimed for the precious essential oil and heartwood. Over-exploitation, diseases, and habitat loss have posed significant challenges to find an alternative bioresource for biomass production. Here, we report the successful growth of in vitro grown somatic embryos in 10 L air-lift bioreactors. Additionally, we characterized arabinogalactan proteins and small molecule constituents such as phenolics and terpenoids that are secreted by the suspended somatic embryos into the culture media. In parallel to the biochemical characterisation, we followed the entire developmental progression of proembryogenic masses into matured cotyledonary embryos during a single run of the bioreactor. The East Indian sandalwood tree, Santalum album, yields one of the costliest heartwoods and precious essential oil. Unsurprisingly, this endangered forest species is severely affected due to unmet global demands, illegal trade and harvesting, overharvesting and an epidemic mycoplasmal spike disease. In vitro micropropagation endeavours have resulted in defined in vitro stages such as somatic embryos that are amenable to mass production in bioreactors. We report on somatic embryo production in a 10-L air-lift-type bioreactor, and compare the growth and biochemical parameters with those of a 2-L air-lift-type bioreactor. For the 10-L bioreactor with biomass (475.7 ± 18 g fresh weight; P < 0.01), concomitantly santalols (5.2 ± 0.15 mg L−1; P < 0.05), phenolics (31 ± 1.6 mg L−1) and arabinogalactan proteins (AGPs) (39 ± 3.1 mg L−1; P < 0.05) are produced in 28 days. In addition, we identified and quantified several santalols and phenolics by means of high-performance thin-layer chromatography and reverse-phase high-pressure liquid chromatography analyses, respectively. Results indicate that 10-L-capacity air-lift bioreactors are capable of supporting somatic embryo cultures, while the extracellular medium provides opportunities for production of industrial raw materials such as santalols, phenolics and AGPs. This will prove useful for further optimization and scale-up studies of plant-produced metabolites.
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