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Tarelkina TV, Novitskaya LL, Galibina NA, Moshchenskaya YL, Nikerova KM, Nikolaeva NN, Sofronova IN, Ivanova DS, Semenova LI. Expression Analysis of Key Auxin Biosynthesis, Transport, and Metabolism Genes of Betula pendula with Special Emphasis on Figured Wood Formation in Karelian Birch. PLANTS 2020; 9:plants9111406. [PMID: 33105649 PMCID: PMC7690449 DOI: 10.3390/plants9111406] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 10/19/2020] [Accepted: 10/20/2020] [Indexed: 12/31/2022]
Abstract
Auxin status in woody plants is believed to be a critical factor for the quantity and quality of the wood formed. It has been previously demonstrated that figured wood formation in Karelian birch (Betula pendula Roth var. carelica (Merckl.) Hämet-Ahti) is associated with a reduced auxin level and elevated sugar content in the differentiating xylem, but the molecular mechanisms of the abnormal xylogenesis remained largely unclear. We have identified genes involved in auxin biosynthesis (Yucca), polar auxin transport (PIN) and the conjugation of auxin with amino acids (GH3) and UDP-glucose (UGT84B1) in the B. pendula genome, and analysed their expression in trunk tissues of trees differing in wood structure. Almost all the investigated genes were overexpressed in Karelian birch trunks. Although Yucca genes were overexpressed, trunk tissues in areas developing figured grain had traits of an auxin-deficient phenotype. Overexpression of GH3s and UGT84B1 appears to have a greater effect on figured wood formation. Analysis of promoters of the differentially expressed genes revealed a large number of binding sites with various transcription factors associated with auxin and sugar signalling. These data agree with the hypothesis that anomalous figured wood formation in Karelian birch may be associated with the sugar induction of auxin conjugation.
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Tomescu AMF, Groover AT. Mosaic modularity: an updated perspective and research agenda for the evolution of vascular cambial growth. THE NEW PHYTOLOGIST 2019; 222:1719-1735. [PMID: 30552764 DOI: 10.1111/nph.15640] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 11/28/2018] [Indexed: 06/09/2023]
Abstract
Secondary growth from a vascular cambium, present today only in seed plants and isoetalean lycophytes, has a 400-million-yr evolutionary history that involves considerably broader taxonomic diversity, most of it hidden in the fossil record. Approaching vascular cambial growth as a complex developmental process, we review data from living plants and fossils that reveal diverse modes of secondary growth. These are consistent with a modular nature of secondary growth, when considered as a tracheophyte-wide structural feature. This modular perspective identifies putative constituent developmental modules of cambial growth, for which we review developmental anatomy and regulation. Based on these data, we propose a hypothesis that explains the sources of diversity of secondary growth, considered across the entire tracheophyte clade, and opens up new avenues for exploring the origin of secondary growth. In this hypothesis, various modes of secondary growth reflect a mosaic pattern of expression of different developmental-regulatory modules among different lineages. We outline an approach that queries three information systems (living seed plants, living seed-free plants, and fossils) and integrates data on developmental regulation, anatomy, gene evolution and phylogeny to test the mosaic modularity hypothesis and its implications, and to inform efforts aimed at understanding the evolution of secondary growth.
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Affiliation(s)
- Alexandru M F Tomescu
- Department of Biological Sciences, Humboldt State University, Arcata, CA, 95521, USA
| | - Andrew T Groover
- Pacific Southwest Research Station, USDA Forest Service, Davis, CA, 95618, USA
- Department of Plant Biology, University of California, Davis, CA, 95616, USA
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Gan Z, Wang Y, Wu T, Xu X, Zhang X, Han Z. MdPIN1b encodes a putative auxin efflux carrier and has different expression patterns in BC and M9 apple rootstocks. PLANT MOLECULAR BIOLOGY 2018; 96:353-365. [PMID: 29340953 DOI: 10.1007/s11103-018-0700-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 01/08/2018] [Indexed: 06/07/2023]
Abstract
Lower promoter activity is closely associated with lower MdPIN1b expression in the M9 interstem, which might contribute to the dwarfing effect in apple trees. Apple trees grafted onto dwarfing rootstock Malling 9 (M9) produce dwarfing tree architecture with high yield and widely applying in production. Previously, we have reported that in Malus 'Red Fuji' (RF) trees growing on M9 interstem and Baleng Crab (BC) rootstock, IAA content was relatively higher in bark tissue of M9 interstem than that in scion or rootstock. As IAA polar transportation largely depends on the PIN-FORMED (PIN) auxin efflux carrier. Herein, we identify two putative auxin efflux carrier genes in Malus genus, MdPIN1a and MdPIN1b, which were closely related to the AtPIN1. We found that MdPIN1b was expressed preferentially in BC and M9, and the expression of MdPIN1b was significantly lower in the phloem of M9 interstem than that in the scion and rootstock. The distinct expression of MdPIN1b and IAA content were concentrated in the cambium and adjacent xylem or phloem, and MdPIN1b protein was localized on cell plasma membrane in onion epidermal cells transiently expressing 35S:MdPIN1b-GFP fusion protein. Interestingly, an MdPIN1b mutant allele in the promoter region upstream of M9 exhibited decreased MdPIN1b expression compared to BC. MdPIN1b over-expressing interstem in tobacco exhibited increased polar auxin transport. It is proposed that natural allelic differences decreased promoter activity is closely associated with lower MdPIN1b expression in the M9 interstem, which might limit the basipetal transport of auxin, and in turn might contribute to the dwarfing effect. Taken together, these results reveal allelic variation underlying an important apple rootstock trait, and specifically a novel molecular genetic mechanism underlying dwarfing mechanism.
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Affiliation(s)
- Zengyu Gan
- Institute of Horticultural Plants, College of Horticulture, China Agricultural University, Beijing, 100193, People's Republic of China
- Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China Agricultural University, Beijing, 100193, People's Republic of China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology) in Ministry of Agriculture, China Agricultural University, Beijing, 100193, People's Republic of China
| | - Yi Wang
- Institute of Horticultural Plants, College of Horticulture, China Agricultural University, Beijing, 100193, People's Republic of China
- Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China Agricultural University, Beijing, 100193, People's Republic of China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology) in Ministry of Agriculture, China Agricultural University, Beijing, 100193, People's Republic of China
| | - Ting Wu
- Institute of Horticultural Plants, College of Horticulture, China Agricultural University, Beijing, 100193, People's Republic of China
- Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China Agricultural University, Beijing, 100193, People's Republic of China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology) in Ministry of Agriculture, China Agricultural University, Beijing, 100193, People's Republic of China
| | - Xuefeng Xu
- Institute of Horticultural Plants, College of Horticulture, China Agricultural University, Beijing, 100193, People's Republic of China
- Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China Agricultural University, Beijing, 100193, People's Republic of China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology) in Ministry of Agriculture, China Agricultural University, Beijing, 100193, People's Republic of China
| | - Xinzhong Zhang
- Institute of Horticultural Plants, College of Horticulture, China Agricultural University, Beijing, 100193, People's Republic of China
- Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China Agricultural University, Beijing, 100193, People's Republic of China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology) in Ministry of Agriculture, China Agricultural University, Beijing, 100193, People's Republic of China
| | - Zhenhai Han
- Institute of Horticultural Plants, College of Horticulture, China Agricultural University, Beijing, 100193, People's Republic of China.
- Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China Agricultural University, Beijing, 100193, People's Republic of China.
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology) in Ministry of Agriculture, China Agricultural University, Beijing, 100193, People's Republic of China.
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Brackmann K, Greb T. Long- and short-distance signaling in the regulation of lateral plant growth. PHYSIOLOGIA PLANTARUM 2014; 151:134-41. [PMID: 24053438 PMCID: PMC4282381 DOI: 10.1111/ppl.12103] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 08/19/2013] [Indexed: 05/08/2023]
Abstract
Lateral growth of shoot and root axes by the formation of secondary vascular tissues is an instructive example for the plasticity of plant growth processes. Being purely postembryonic, lateral growth strongly depends on environmental input and is tightly regulated by long- and short-distance signaling. In general, plant vasculature represents the main route for long-distance transport of compounds throughout the plant body, thereby providing also a fast and efficient signaling pipeline for the coordination of growth and development. The vasculature consists of three major tissues; the xylem conducts water and nutrients, the phloem transports mainly organic compounds and the vascular cambium is a group of undifferentiated stem cells responsible for the continuous production of secondary vascular tissues. Notably, the close proximity to functional vascular tissues makes the vascular cambium especially accessible for the regulation by long-distance-derived signaling molecules as well as by the physical and physiological properties of transport streams. Thus, the vascular cambium offers unique opportunities for studying the complex regulation of plant growth processes. In this review, we focus on recent findings about long- and short-distance signaling mechanisms regulating cambium activity and, thereby, lateral expansion of plant growth axes by the formation of additional vascular tissues.
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Affiliation(s)
- Klaus Brackmann
- Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of SciencesDr. Bohr-Gasse 3, AT-1030, Vienna, Austria
| | - Thomas Greb
- Correspondence Corresponding author, e-mail:
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Trupiano D, Rocco M, Renzone G, Scaloni A, Rossi M, Viscosi V, Chiatante D, Scippa GS. Temporal analysis of poplar woody root response to bending stress. PHYSIOLOGIA PLANTARUM 2014; 150:174-193. [PMID: 23683290 DOI: 10.1111/ppl.12072] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 03/27/2013] [Accepted: 05/03/2013] [Indexed: 06/02/2023]
Abstract
Temperate perennial woody plants use different environmental signals to coordinate their growth and development in relation to seasonal changes. Preliminary evidences suggest that, even during dormancy, plants maintain effective metabolic activities and molecular mechanisms ensuring them an eventual recording of mechanical loads during winter times. Despite their great importance for productivity and survival, plant biology investigations have poorly characterized the root growth cycle and its response to environmental stresses. In this study, we describe the proteomic changes occurring over the time in poplar root either in the absence or in response to a bending stress; corresponding expression of cell cycle regulator and auxin transporter genes was also evaluated by reverse transcription polymerase chain reaction analysis. Our results confirm previous evidences on the effect of the bending stress on the anticipation of root growth resumption, providing additional insights on a temporal modulation of various plant metabolic processes involved in dormancy break, growth resumption and stress response in the bent root; these events seem related to the differential compression and tension force distribution occurring over the plant taproot.
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Affiliation(s)
- Dalila Trupiano
- Dipartimento di Bioscienze e Territorio, University of Molise, 86090 , Pesche, IS, Italy
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Carraro N, Tisdale-Orr TE, Clouse RM, Knöller AS, Spicer R. Diversification and Expression of the PIN, AUX/LAX, and ABCB Families of Putative Auxin Transporters in Populus. FRONTIERS IN PLANT SCIENCE 2012; 3:17. [PMID: 22645571 PMCID: PMC3355733 DOI: 10.3389/fpls.2012.00017] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2011] [Accepted: 01/17/2012] [Indexed: 05/21/2023]
Abstract
Intercellular transport of the plant hormone auxin is mediated by three families of membrane-bound protein carriers, with the PIN and ABCB families coding primarily for efflux proteins and the AUX/LAX family coding for influx proteins. In the last decade our understanding of gene and protein function for these transporters in Arabidopsis has expanded rapidly but very little is known about their role in woody plant development. Here we present a comprehensive account of all three families in the model woody species Populus, including chromosome distribution, protein structure, quantitative gene expression, and evolutionary relationships. The PIN and AUX/LAX gene families in Populus comprise 16 and 8 members respectively and show evidence for the retention of paralogs following a relatively recent whole genome duplication. There is also differential expression across tissues within many gene pairs. The ABCB family is previously undescribed in Populus and includes 20 members, showing a much deeper evolutionary history, including both tandem and whole genome duplication as well as probable gene loss. A striking number of these transporters are expressed in developing Populus stems and we suggest that evolutionary and structural relationships with known auxin transporters in Arabidopsis can point toward candidate genes for further study in Populus. This is especially important for the ABCBs, which is a large family and includes members in Arabidopsis that are able to transport other substrates in addition to auxin. Protein modeling, sequence alignment and expression data all point to ABCB1.1 as a likely auxin transport protein in Populus. Given that basipetal auxin flow through the cambial zone shapes the development of woody stems, it is important that we identify the full complement of genes involved in this process. This work should lay the foundation for studies targeting specific proteins for functional characterization and in situ localization.
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Affiliation(s)
- Nicola Carraro
- Department of Horticulture and Landscape Architecture, Purdue UniversityWest Lafayette, IN, USA
| | | | - Ronald Matthew Clouse
- Division of Invertebrate Zoology, American Museum of Natural HistoryNew York, NY, USA
| | - Anne Sophie Knöller
- Department of Mathematics and Computer Science, Philipps UniversityMarburg, Germany
| | - Rachel Spicer
- Department of Botany, Connecticut CollegeNew London, CT, USA
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Ache P, Fromm J, Hedrich R. Potassium-dependent wood formation in poplar: seasonal aspects and environmental limitations. PLANT BIOLOGY (STUTTGART, GERMANY) 2010; 12:259-67. [PMID: 20398233 DOI: 10.1111/j.1438-8677.2009.00282.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Potassium availability and acquisition are pivotal for the generation of biomass and thus wood formation in growing poplar trees. Here, we focus on the role of potassium (K(+)) in wood production, transitions between dormancy and active growth, and limiting environmental conditions. Molecular mechanisms, such as expression and activity of K(+) transporters and channels controlling seasonal changes in wood formation, are discussed.
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Affiliation(s)
- P Ache
- Universität Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Würzburg, Germany.
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Björklund S, Antti H, Uddestrand I, Moritz T, Sundberg B. Cross-talk between gibberellin and auxin in development of Populus wood: gibberellin stimulates polar auxin transport and has a common transcriptome with auxin. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 52:499-511. [PMID: 17825053 DOI: 10.1111/j.1365-313x.2007.03250.x] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Both indole acetic acid (IAA) and gibberellins (GAs) stimulate cell and organ growth. We have examined GA/IAA cross-talk in cambial growth of hybrid aspen (Populus tremulaxtremuloides). Decapitated trees were fed with IAA and GA, alone and in combination. Endogenous hormone levels after feeding were measured, by mass spectrometry, in the stem tissues below the point of application. These stem tissues with defined hormone balances were also used for global transcriptome analysis, and the abundance of selected transcripts was measured by real-time reverse-transcription polymerase chain reaction. By feeding isotope-labeled IAA, we demonstrated that GA increases auxin levels in the stem by stimulating polar auxin transport. This finding adds a new dimension to the concept that the endogenous GA/IAA balance in plants is determined by cross-talk between the two hormones. We also show that GA has a common transcriptome with auxin, including many transcripts related to cell growth. This finding provides molecular support to physiological experiments demonstrating that either hormone can induce growth if the other hormone is absent/deficient because of mutations or experimental treatments. It also highlights the potential for extensive cross-talk between GA- and auxin-induced responses in vegetative growth of the intact plant. The role of endogenous IAA and GA in wood development is discussed.
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Affiliation(s)
- Simon Björklund
- Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE 901 83 Umeå, Sweden
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Schrader J, Moyle R, Bhalerao R, Hertzberg M, Lundeberg J, Nilsson P, Bhalerao RP. Cambial meristem dormancy in trees involves extensive remodelling of the transcriptome. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 40:173-87. [PMID: 15447645 DOI: 10.1111/j.1365-313x.2004.02199.x] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The establishment of the dormant state in meristems involves considerable physiological and metabolic alterations necessary for surviving unfavourable growth conditions. However, a global molecular analysis of dormancy in meristems has been hampered by the difficulty in isolating meristem cells. We used cryosectioning to isolate purified cambial meristem cells from the woody plant Populus tremula during active growth and dormancy. These samples were used to generate meristem-specific cDNA libraries and for cDNA microarray experiments to define the global transcriptional changes underlying cambial dormancy. The results indicate a significant reduction in the complexity of the cambial transcriptome in the dormant state. Although cell division is terminated in the dormant cambium, the cell cycle machinery appears to be maintained in a skeletal state as suggested by the continued presence of transcripts for several cell cycle regulators. The downregulation of PttPIN1 and PttPIN2 transcripts explains the reduced basipetal polar auxin transport during dormancy. The induction of a member of the SINA family of ubiquitin ligases implicated in auxin signalling indicates a potential mechanism for modulation of auxin sensitivity during cambial dormancy. The metabolic alterations during dormancy are mirrored in the induction of genes involved in starch breakdown and the glyoxysomal cycle. Interestingly, the induction of RGA1 like gene suggests modification of gibberellin signalling in cambial dormancy. The induction of genes such as poplar orthologues of FIE and HAP2 indicates a potential role for these global regulators of transcription in orchestrating extensive changes in gene expression during dormancy.
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Affiliation(s)
- Jarmo Schrader
- Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden
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Schrader J, Baba K, May ST, Palme K, Bennett M, Bhalerao RP, Sandberg G. Polar auxin transport in the wood-forming tissues of hybrid aspen is under simultaneous control of developmental and environmental signals. Proc Natl Acad Sci U S A 2003; 100:10096-101. [PMID: 12909722 PMCID: PMC187777 DOI: 10.1073/pnas.1633693100] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2002] [Indexed: 12/24/2022] Open
Abstract
Recent research has highlighted the importance of auxin concentration gradients during plant development. Establishment of these gradients is believed to involve polar auxin transport through specialized carrier proteins. We have used an experimental system, the wood-forming tissue of hybrid aspen, which allows tissue-specific expression analysis of auxin carrier genes and quantification of endogenous concentrations of the hormone. As part of this study, we isolated the putative polar auxin transport genes, PttLAX1-PttLAX3 and PttPIN1-PttPIN3, belonging to the AUX1-like family of influx and PIN1-like efflux carriers, respectively. Analysis of PttLAX and PttPIN expression suggests that specific positions in a concentration gradient of the hormone are associated with different stages of vascular cambium development and expression of specific members of the auxin transport gene families. We were also able demonstrate positive feedback of auxin on polar auxin transport genes. Entry into dormancy at the end of a growing season leads to a loss of auxin transport capacity, paralleled by reduced expression of PttLAX and PttPIN genes. Furthermore, data from field experiments show that production of the molecular components of the auxin transport machinery is governed by environmental controls. Our findings collectively demonstrate that trees have developed mechanisms to modulate auxin transport in the vascular meristem in response to developmental and environmental cues.
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Affiliation(s)
- J Schrader
- Umeå Plant Science Centre, Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden
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Arend M, Weisenseel MH, Brummer M, Osswald W, Fromm JH. Seasonal changes of plasma membrane H(+)-ATPase and endogenous ion current during cambial growth in poplar plants. PLANT PHYSIOLOGY 2002; 129:1651-63. [PMID: 12177478 PMCID: PMC166753 DOI: 10.1104/pp.003905] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2002] [Revised: 03/12/2002] [Accepted: 05/03/2002] [Indexed: 05/18/2023]
Abstract
The plasma membrane H(+)-ATPase (PM H(+)-ATPase), potassium ions, and endogenous ion currents might play a fundamental role in the physiology of cambial growth. Seasonal changes of these parameters were studied in twigs of Populus nigra and Populus trichocarpa. Monoclonal and polyclonal antibodies against the PM H(+)-ATPase, x-ray analysis for K(+) localization and a vibrating electrode for measurement of endogenous ion currents were used as probes. In dormant plants during autumn and winter, only a slight immunoreactivity against the PM H(+)-ATPase was found in cross sections and tissue homogenates, K(+) was distributed evenly, and the density of endogenous current was low. In spring during cambial growth, strong immunoreactivity against a PM H(+)-ATPase was observed in cambial cells and expanding xylem cells using the monoclonal antibody 46 E5 B11 F6 for fluorescence microscopy and transmission electron microscopy. At the same time, K(+) accumulated in cells of the cambial region, and strong endogenous current was measured in the cambial and immature xylem zone. Addition of auxin to dormant twigs induced the formation of this PM H(+)-ATPase in the dormant cambial region within a few days and an increase in density of endogenous current in shoot cuttings within a few hours. The increase in PM H(+)-ATPase abundance and in current density by auxin indicates that auxin mediates a rise in number and activity of an H(+)-ATPase in the plasma membrane of cambial cells and their derivatives. This PM H(+)-ATPase generates the necessary H(+)-gradient (proton-motive force) for the uptake of K(+) and nutrients into cambial and expanding xylem cells.
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Affiliation(s)
- Matthias Arend
- Fachgebeit Angewandte Holzbiologie, Technische Universität München, Munich, Germany.
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12
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Abstract
The beautiful patterns apparent in wood grain have their origin in the alignment of fusiform initial cells in the vascular cambium of trees. We develop a mathematical model to describe the orientation of fusiform initial cells, and their interaction with the plant hormone indole-3-acetic acid (auxin). The model incorporates the following four assumptions: (1) auxin is actively transported parallel to the long axis of the initials, (2) auxin diffuses perpendicular to the long axis of the initials, (3) the initials tend to orient parallel to the flux of auxin through the cambium, and (4) adjacent initials tend to orient parallel to one another. Each assumption is justified on the basis of available evidence and cast in mathematical form. Our main result is a pair of nonlinear differential equations that describe the coupling between the distribution of auxin in the cambium and the orientation of fusiform initials. Numerical solutions to the equations show qualitative resemblance to the wood grain patterns observed at branch junctions, wounds and knots, and topological defects.
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Affiliation(s)
- Eric M Kramer
- Physics Department, Simon's Rock College, 84 Alford Road, Great Barrington, MA 01230, USA.
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Abstract
A mathematical model is presented to describe the coupling between the concentration of indole-3-acetic acid (IAA) in the cambial region of a tree branch and the radial expansion of the branch during active growth. The main features of the model are (1) the branch cambium is treated as an approximately cylindrical surface of negligible thickness, (2) the rate of radial growth is proportional to the mass of IAA per unit area on the cambial surface, and (3) IAA is transported basipetally through the cambium at a constant speed. We neglect the role of elastic strains in the determination of branch shape, and the effects of IAA synthesis and metabolization in the cambium, so the model is not quantitatively accurate. However, the model does reproduce several important qualitative features of tree growth including the approximate area-preserving property of tree branch junctions and the ability of a branch to maintain its shape despite perturbations due to injury.
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Affiliation(s)
- E M Kramer
- Physics Department, Simon's Rock College, Great Barrington, MA, 01230, USA.
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Lachaud S, Catesson AM, Bonnemain JL. Structure and functions of the vascular cambium. COMPTES RENDUS DE L'ACADEMIE DES SCIENCES. SERIE III, SCIENCES DE LA VIE 1999; 322:633-50. [PMID: 10505236 DOI: 10.1016/s0764-4469(99)80103-6] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Following a general outline on the functioning of the cambium, the authors review the data acquired over the last 20 years. The interest is focused on: i) the ultrastructural characteristics of the two kinds of initials; ii) the early structural, metabolic and molecular modifications occurring during the first stages of daughter cell differentiation into either xylem or phloem; iii) the complex rhythmic changes of structure, metabolism and activity undergone by cambial cells during the seasonal cycle; iv) the characteristics and control of the cessation of cambial activity in autumn and of its reactivation in spring; v) the main research approaches in cell and molecular biology presently open to the students of the cambial meristem.
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Affiliation(s)
- S Lachaud
- Laboratoire de physiologie et biochimie végétales, ESA 6161 CNSR, Université de Pointers, France
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Catesson AM, Lachaud S. Le cambium, structure, fonctionnement et contrôle de l'activité saisonnière. ACTA ACUST UNITED AC 1993. [DOI: 10.1080/12538078.1993.10515605] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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16
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