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Conti L, Bradley D. TERMINAL FLOWER1 is a mobile signal controlling Arabidopsis architecture. THE PLANT CELL 2007; 19:767-78. [PMID: 17369370 PMCID: PMC1867375 DOI: 10.1105/tpc.106.049767] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Shoot meristems harbor stem cells that provide key growing points in plants, maintaining themselves and generating all above-ground tissues. Cell-to-cell signaling networks maintain this population, but how are meristem and organ identities controlled? TERMINAL FLOWER1 (TFL1) controls shoot meristem identity throughout the plant life cycle, affecting the number and identity of all above-ground organs generated; tfl1 mutant shoot meristems make fewer leaves, shoots, and flowers and change identity to flowers. We find that TFL1 mRNA is broadly distributed in young axillary shoot meristems but later becomes limited to central regions, yet affects cell fates at a distance. How is this achieved? We reveal that the TFL1 protein is a mobile signal that becomes evenly distributed across the meristem. TFL1 does not enter cells arising from the flanks of the meristem, thus allowing primordia to establish their identity. Surprisingly, TFL1 movement does not appear to occur in mature shoots of leafy (lfy) mutants, which eventually stop proliferating and convert to carpel/floral-like structures. We propose that signals from LFY in floral meristems may feed back to promote TFL1 protein movement in the shoot meristem. This novel feedback signaling mechanism would ensure that shoot meristem identity is maintained and the appropriate inflorescence architecture develops.
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Affiliation(s)
- Lucio Conti
- Cell and Developmental Biology, John Ines Centre, Colney, Norwich, NR4 7UH, United Kingdom
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53
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Laitinen RAE, Broholm S, Albert VA, Teeri TH, Elomaa P. Patterns of MADS-box gene expression mark flower-type development in Gerbera hybrida (Asteraceae). BMC PLANT BIOLOGY 2006; 6:11. [PMID: 16762082 PMCID: PMC1525168 DOI: 10.1186/1471-2229-6-11] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Accepted: 06/09/2006] [Indexed: 05/10/2023]
Abstract
BACKGROUND The inflorescence of the cut-flower crop Gerbera hybrida (Asteraceae) consists of two principal flower types, ray and disc, which form a tightly packed head, or capitulum. Despite great interest in plant morphological evolution and the tractability of the gerbera system, very little is known regarding genetic mechanisms involved in flower type specification. Here, we provide comparative staging of ray and disc flower development and microarray screening for differentially expressed genes, accomplished via microdissection of hundreds of coordinately developing flower primordia. RESULTS Using a 9K gerbera cDNA microarray we identified a number of genes with putative specificity to individual flower types. Intrestingly, several of these encode homologs of MADS-box transcription factors otherwise known to regulate flower organ development. From these and previously obtained data, we hypothesize the functions and protein-protein interactions of several gerbera MADS-box factors. CONCLUSION Our RNA expression results suggest that flower-type specific MADS protein complexes may play a central role in differential development of ray and disc flowers across the gerbera capitulum, and that some commonality is shared with known protein functions in floral organ determination. These findings support the intriguing conjecture that the gerbera flowering head is more than a mere floral analog at the level of gene regulation.
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Affiliation(s)
- Roosa AE Laitinen
- Department of Applied Biology, P.O.Box 27, 00014 University of Helsinki, Finland
| | - Suvi Broholm
- Department of Applied Biology, P.O.Box 27, 00014 University of Helsinki, Finland
| | - Victor A Albert
- Natural History Museum, University of Oslo, P.O.Box 1172, Blindern, NO-0318 Oslo, Norway
| | - Teemu H Teeri
- Department of Applied Biology, P.O.Box 27, 00014 University of Helsinki, Finland
| | - Paula Elomaa
- Department of Applied Biology, P.O.Box 27, 00014 University of Helsinki, Finland
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54
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Fleming AJ. Leaf initiation: the integration of growth and cell division. PLANT MOLECULAR BIOLOGY 2006; 60:905-14. [PMID: 16724260 DOI: 10.1007/s11103-005-7703-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Accepted: 05/21/2005] [Indexed: 05/09/2023]
Abstract
The shoot apical meristem of higher plants is characterized by a conserved pattern of cell division, the functional significance of which is unclear. Although a causal role for cell division frequency and orientation in morphogenesis has been suggested, supporting data are limited. An alternative interpretation laying stress on the control of growth vector and its integration with networks of transcription factors and hormonal signals is discussed in this review.
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Affiliation(s)
- Andrew J Fleming
- Department of Animal and Plant Sciences, University of Sheffield, Western Bank, S10 2TN, Sheffield, UK.
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55
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Aida M, Tasaka M. Morphogenesis and patterning at the organ boundaries in the higher plant shoot apex. PLANT MOLECULAR BIOLOGY 2006; 60:915-28. [PMID: 16724261 DOI: 10.1007/s11103-005-2760-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2004] [Accepted: 09/02/2005] [Indexed: 05/09/2023]
Abstract
Formation of lateral organ primordia from the shoot apical meristem creates boundaries that separate the primordium from surrounding tissue. Morphological and gene expression studies indicate the presence of a distinct set of cells that define the boundaries in the plant shoot apex. Cells at the boundary usually display reduced growth activity that results in separation of adjacent organs or tissues and this morphological boundary coincides with the border of different cell identities. Such morphogenetic and patterning events and their spatial coordination are controlled by a number of boundary-specific regulatory genes. The boundary may also act as a reference point for the generation of new meristems such as axillary meristems. Many of the genes involved in meristem initiation are expressed in the boundary. This review summarizes the cellular characters of the shoot organ boundary and the roles of regulatory genes that control different aspects of this unique region in plant development.
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Affiliation(s)
- Mitsuhiro Aida
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Nara, 630-0192, Japan.
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56
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Carraro N, Peaucelle A, Laufs P, Traas J. Cell differentiation and organ initiation at the shoot apical meristem. PLANT MOLECULAR BIOLOGY 2006; 60:811-26. [PMID: 16724254 DOI: 10.1007/s11103-005-2761-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2005] [Accepted: 09/02/2005] [Indexed: 05/09/2023]
Abstract
Plants continuously generate organs at the flanks of their shoot apical meristems (SAMs). The patterns in which these organs are initiated, also called patterns of phyllotaxis, are highly stereotypic and characteristic for a particular species or developmental stage. This stable, predictable behaviour of the meristem has led to the idea that organ initiation must be based on simple and robust mechanisms. This conclusion is less evident, however, if we consider the very dynamic behaviour of the individual cells. How dynamic cellular events are coordinated and how they are linked to the regular patterns of organ initiation is a major issue in plant developmental biology.
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Affiliation(s)
- Nicola Carraro
- Laboratoire de Biologie Cellulaire, INRA, Institut Jean-Pierre Bourgin, Route de Saint Cyr, 78026, Versailles, cedex, France
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57
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Kurdyukov S, Faust A, Nawrath C, Bär S, Voisin D, Efremova N, Franke R, Schreiber L, Saedler H, Métraux JP, Yephremov A. The epidermis-specific extracellular BODYGUARD controls cuticle development and morphogenesis in Arabidopsis. THE PLANT CELL 2006; 18:321-39. [PMID: 16415209 PMCID: PMC1356542 DOI: 10.1105/tpc.105.036079] [Citation(s) in RCA: 205] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The outermost epidermal cell wall is specialized to withstand pathogens and natural stresses, and lipid-based cuticular polymers are the major barrier against incursions. The Arabidopsis thaliana mutant bodyguard (bdg), which exhibits defects characteristic of the loss of cuticle structure not attributable to a lack of typical cutin monomers, unexpectedly accumulates significantly more cell wall-bound lipids and epicuticular waxes than wild-type plants. Pleiotropic effects of the bdg mutation on growth, viability, and cell differentiation are also observed. BDG encodes a member of the alpha/beta-hydrolase fold protein superfamily and is expressed exclusively in epidermal cells. Using Strep-tag epitope-tagged BDG for mutant complementation and immunolocalization, we show that BDG is a polarly localized protein that accumulates in the outermost cell wall in the epidermis. With regard to the appearance and structure of the cuticle, the phenotype conferred by bdg is reminiscent of that of transgenic Arabidopsis plants that express an extracellular fungal cutinase, suggesting that bdg may be incapable of completing the polymerization of carboxylic esters in the cuticular layer of the cell wall or the cuticle proper. We propose that BDG codes for an extracellular synthase responsible for the formation of cuticle. The alternative hypothesis proposes that BDG controls the proliferation/differentiation status of the epidermis via an unknown mechanism.
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58
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Kramer EM, Jaramillo MA. Genetic basis for innovations in floral organ identity. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2006; 304:526-35. [PMID: 15880769 DOI: 10.1002/jez.b.21046] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Of the many innovations associated with the radiation of the angiosperms, the evolution of a petal identity program is among the best understood from a genetic standpoint. Although the existing data do indicate that similar genetic mechanisms control petal development across diverse taxa, there is also considerable evidence for variability in petal identity programs, likely due to a number of factors. These points are illustrated through a review of our current knowledge on the subject, integrating phylogenetic, morphological, and genetic studies. Comparative studies of petal identity highlight the complex nature of homology in plants and stand as a cautionary tale for the interpretation of gene expression data.
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Affiliation(s)
- Elena M Kramer
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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59
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Kurata T, Okada K, Wada T. Intercellular movement of transcription factors. CURRENT OPINION IN PLANT BIOLOGY 2005; 8:600-5. [PMID: 16182599 DOI: 10.1016/j.pbi.2005.09.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Accepted: 09/12/2005] [Indexed: 05/04/2023]
Abstract
Intercellular communication by the direct trafficking of transcription factors has been reported in plant developmental events such as root radial or epidermal cell patterning and shoot organogenesis. Investigations of this novel communication system have just begun and have highlighted the structural requirements for and mechanisms of transcription factor movement. Early studies suggest that plants employ both targeted (selective) and non-targeted (non-selective) intercellular movement of transcription factors. Factors that affect the intercellular movement of transcription factors through plasmodesmata have been explored.
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Affiliation(s)
- Tetsuya Kurata
- Plant Science Center, RIKEN, 1-7-22 Suehiro-cho, Tsurumi-ku, Kanagawa 230-0045, and Department of Botany, Graduate School of Science, Kyoto University, Japan
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60
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Lee JY, Taoka KI, Yoo BC, Ben-Nissan G, Kim DJ, Lucas WJ. Plasmodesmal-associated protein kinase in tobacco and Arabidopsis recognizes a subset of non-cell-autonomous proteins. THE PLANT CELL 2005; 17:2817-31. [PMID: 16126836 PMCID: PMC1242275 DOI: 10.1105/tpc.105.034330] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2005] [Revised: 07/22/2005] [Accepted: 08/04/2005] [Indexed: 05/04/2023]
Abstract
Cell-to-cell communication in plants involves the trafficking of macromolecules through specialized intercellular organelles, termed plasmodesmata. This exchange of proteins and RNA is likely regulated, and a role for protein phosphorylation has been implicated, but specific components remain to be identified. Here, we describe the molecular characterization of a plasmodesmal-associated protein kinase (PAPK). A 34-kD protein, isolated from a plasmodesmal preparation, exhibits calcium-independent kinase activity and displays substrate specificity in that it recognizes a subset of viral and endogenous non-cell-autonomous proteins. This PAPK specifically phosphorylates the C-terminal residues of tobacco mosaic virus movement protein (TMV MP); this posttranslational modification has been shown to affect MP function. Molecular analysis of purified protein established that tobacco (Nicotiana tabacum) PAPK is a member of the casein kinase I family. Subcellular localization studies identified a possible Arabidopsis thaliana PAPK homolog, PAPK1. TMV MP and PAPK1 are colocalized within cross-walls in a pattern consistent with targeting to plasmodesmata. Moreover, Arabidopsis PAPK1 also phosphorylates TMV MP in vitro at its C terminus. These results strongly suggest that Arabidopsis PAPK1 is a close homolog of tobacco PAPK. Thus, PAPK1 represents a novel plant protein kinase that is targeted to plasmodesmata and may play a regulatory role in macromolecular trafficking between plant cells.
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Affiliation(s)
- Jung-Youn Lee
- Section of Plant Biology, Division of Biological Sciences, University of California, Davis, CA 95616, USA.
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61
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Kim JY, Rim Y, Wang J, Jackson D. A novel cell-to-cell trafficking assay indicates that the KNOX homeodomain is necessary and sufficient for intercellular protein and mRNA trafficking. Genes Dev 2005; 19:788-93. [PMID: 15805469 PMCID: PMC1074316 DOI: 10.1101/gad.332805] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Cell-to-cell trafficking of regulatory proteins is a novel mechanism for communication during cell fate specification in plants. Although several developmental proteins traffic cell-to-cell, no signals that are both necessary and sufficient for this function in developmental proteins have been described. We developed a novel trafficking assay using trichome rescue in Arabidopsis. Fusion to KNOTTED1 (KN1) conferred gain-of-trafficking function to the cell-autonomous GLABROUS1 (GL1) protein. We show that the KNOX homeodomain (HD) is necessary and sufficient for intercellular trafficking, identifying a novel function for the HD as the minimal sequence required for trafficking of KN1 and its associated mRNA.
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Affiliation(s)
- Jae-Yean Kim
- Division of Applied Life Science (BK21 program), Environmental Biotechnology National Core Research Center, PMBBRC, Gyeongsang National University, Jinju 660-701, Korea.
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62
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Kim JY. Regulation of short-distance transport of RNA and protein. CURRENT OPINION IN PLANT BIOLOGY 2005; 8:45-52. [PMID: 16207533 DOI: 10.1016/j.pbi.2004.11.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The intercellular trafficking of proteins and RNAs has emerged as a novel mechanism of cell-cell communication in plant development. Plasmodesmata (PD), intercellular cytoplasmic channels, have a central role in cell-cell trafficking of regulatory proteins and RNAs. Recent studies have demonstrated that plants use either a selective or a non-selective PD trafficking pathway for regulatory proteins. Moreover, plants have developed strategies to regulate both selective and non-selective movement. Recent work has focused especially on integrating the recent understanding of the function and mechanisms of intercellular macromolecule movement through PD.
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Affiliation(s)
- Jae-Yean Kim
- Division of Applied Life Science, Plant Molecular Biology and Biotechnology Research Center, Environmental Biotechnology National Core Research Center, Gyeongsang National University, Jinju 660-701, Korea.
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63
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Gallagher KL, Paquette AJ, Nakajima K, Benfey PN. Mechanisms regulating SHORT-ROOT intercellular movement. Curr Biol 2005; 14:1847-51. [PMID: 15498493 DOI: 10.1016/j.cub.2004.09.081] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2004] [Revised: 08/25/2004] [Accepted: 08/25/2004] [Indexed: 11/26/2022]
Abstract
Signaling centers within developing organs regulate morphogenesis in both plants and animals. The putative transcription factor SHORT-ROOT (SHR) is an organizing signal regulating the division of specific stem cells in the Arabidopsis root. Comparison of gene transcription with protein localization indicates that SHR moves in a highly specific manner from the cells of the stele in which it is synthesized outward. Here, we provide evidence that SHR intercellular trafficking is both regulated and targeted. First, we show that subcellular localization of SHR in the stele is intrinsic to the SHR protein. Next, we show that SHR must be present in the cytoplasm to move, providing evidence that SHR movement is regulated. Finally, we describe an informative new shr allele, in which the protein is present in the cytoplasm yet does not move. Thus, in contrast to proteins that move by a process resembling diffusion, a cytoplasmic pool of SHR is not sufficient for movement.
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64
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Gallagher KL, Benfey PN. Not just another hole in the wall: understanding intercellular protein trafficking. Genes Dev 2005; 19:189-95. [PMID: 15655108 DOI: 10.1101/gad.1271005] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Development and differentiation of multicellular organisms requires cell-to-cell communication. In plants direct signaling and exchange of macromolecules between cells is possible through plasmodesmata. Recently direct exchange of membrane-bound vesicles and organelles has been demonstrated between animal cells through formation of cytoplasmic bridges (tunneling nanotubes) in vitro. Here we review recent developments in cell-to-cell trafficking of macromolecules in plants and animals.
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65
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Stadler R, Wright KM, Lauterbach C, Amon G, Gahrtz M, Feuerstein A, Oparka KJ, Sauer N. Expression of GFP-fusions in Arabidopsis companion cells reveals non-specific protein trafficking into sieve elements and identifies a novel post-phloem domain in roots. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 41:319-31. [PMID: 15634207 DOI: 10.1111/j.1365-313x.2004.02298.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Transgenic Arabidopsis plants were constructed to express a range of GFP-fusion proteins (36-67 kDa) under the companion cell (CC)-specific AtSUC2 promoter. These plants were used to monitor the trafficking of these GFP-fusion proteins from the CCs into the sieve elements (SEs) and their subsequent translocation within and out of the phloem. The results revealed a large size exclusion limit (SEL) (>67 kDa) for the plasmodesmata connecting SEs and CCs in the loading phloem. Membrane-anchored GFP-fusions and a GFP variant targeted to the endoplasmic reticulum (ER) remained inside the CCs and were used as 'zero trafficking' controls. In contrast, free GFP and all soluble GFP-fusions, moved from the CCs into the SEs and were subsequently translocated through the phloem. Phloem unloading and post-phloem transport of these mobile GFP-fusions were studied in root tips, where post-phloem transport occurred only for the free form of GFP. All of the other soluble GFP-fusion variants were unloaded and restricted to a narrow zone of cells immediately adjacent to the mature protophloem. It appears that this domain of cells, which has a peripheral SEL of about 27-36 kDa, allows protein exchange between protophloem SEs and surrounding cells, but restricts general access of large proteins into the root tip. The presented data provide additional information on phloem development in Arabidopsis in relation to the formation of symplasmic domains.
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Affiliation(s)
- Ruth Stadler
- Molekulare Pflanzenphysiologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany
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66
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Bey M, Stüber K, Fellenberg K, Schwarz-Sommer Z, Sommer H, Saedler H, Zachgo S. Characterization of antirrhinum petal development and identification of target genes of the class B MADS box gene DEFICIENS. THE PLANT CELL 2004; 16:3197-215. [PMID: 15539471 PMCID: PMC535868 DOI: 10.1105/tpc.104.026724] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The class B MADS box transcription factors DEFICIENS (DEF) and GLOBOSA (GLO) of Antirrhinum majus together control the organogenesis of petals and stamens. Toward an understanding of how the downstream molecular mechanisms controlled by DEF contribute to petal organogenesis, we conducted expression profiling experiments using macroarrays comprising >11,600 annotated Antirrhinum unigenes. First, four late petal developmental stages were compared with sepals. More than 500 ESTs were identified that comprise a large number of stage-specifically regulated genes and reveal a highly dynamic transcriptional regulation. For identification of DEF target genes that might be directly controlled by DEF, we took advantage of the temperature-sensitive def-101 mutant. To enhance the sensitivity of the profiling experiments, one petal developmental stage was selected, characterized by increased transcriptome changes that reflect the onset of cell elongation processes replacing cell division processes. Upon reduction of the DEF function, 49 upregulated and 52 downregulated petal target genes were recovered. Eight target genes were further characterized in detail by RT-PCR and in situ studies. Expression of genes responding rapidly toward an altered DEF activity is confined to different petal tissues, demonstrating the complexity of the DEF function regulating diverse basic processes throughout petal morphogenesis.
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Affiliation(s)
- Melanie Bey
- Department for Molecular Plant Genetics, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany
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67
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Takahata K, Takeuchi M, Fujita M, Azuma J, Kamada H, Sato F. Isolation of putative glycoprotein gene from early somatic embryo of carrot and its possible involvement in somatic embryo development. PLANT & CELL PHYSIOLOGY 2004; 45:1658-1668. [PMID: 15574842 DOI: 10.1093/pcp/pch188] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Somatic embryogenesis is a unique process in plant cells. For example, embryogenic cells (EC) of carrot (Daucus carota) maintained in a medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) regenerate whole plants via somatic embryogenesis after the depletion of 2,4-D. Although some genes such as C-ABI3 and C-LEC1 have been found to be involved in somatic embryogenesis, the critical molecular and cellular mechanisms for somatic embryogenesis are unknown. To characterize the early mechanism in the induction of somatic embryogenesis, we isolated genes expressed during the early stage of somatic embryogenesis after 2,4-D depletion. Subtractive hybridization screening and subsequent RNA gel blot analysis suggested a candidate gene, Carrot Early Somatic Embryogenesis 1 (C-ESE1). C-ESE1 encodes a protein that has agglutinin and S-locus-glycoprotein domains and its expression is highly specific to primordial cells of somatic embryo. Transgenic carrot cells with reduced expression of C-ESE1 had wide intercellular space and decreased polysaccharides on the cell surface and showed delayed development in somatic embryogenesis. The importance of cell-to-cell attachment in somatic embryogenesis is discussed.
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Affiliation(s)
- Kiminori Takahata
- Department of Plant Gene and Totipotency, Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto, 606-8502 Japan
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68
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Efremova N, Schreiber L, Bär S, Heidmann I, Huijser P, Wellesen K, Schwarz-Sommer Z, Saedler H, Yephremov A. Functional conservation and maintenance of expression pattern of FIDDLEHEAD-like genes in Arabidopsis and Antirrhinum. PLANT MOLECULAR BIOLOGY 2004; 56:821-37. [PMID: 15803418 DOI: 10.1007/s11103-004-5576-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2004] [Accepted: 10/28/2004] [Indexed: 05/07/2023]
Abstract
In Arabidopsis, loss of function of the epidermis-specific FDH gene coding for a putative beta-ketoacyl-CoA synthase results in ectopic organ fusions in mutants. Corresponding mutants are not available for Antirrhinum majus, however, organ fusions can be induced in both species by chloroacetamide inhibitors of beta-ketoacyl-CoA synthases using a chemical genetics approach. We isolated the ortholog of FDH from Antirrhinum majus, the ANTIRRHINUM FIDDLEHEAD (AFI ) gene, and showed that AFI complements fdh when expressed in the epidermis under control of the FDH promoter. Like FDH, the AFI gene exhibits protodermis- and epidermis-specific expression, and its promoter directs the expression of reporter genes to the epidermis in transgenic Antirrhinum and Arabidopsis. We demonstrate down-regulation of the FDH promoter in the epidermis of the ovary septum, thereby supporting the assumption that FDH-like genes may directly facilitate the cell-cell interactions that need to occur during carpel fusion and pollen tube growth. Up-regulation of FDH in the stomium, on the other hand, provides evidence for its possible involvement in cell separation during anther dehiscence. Down-regulation of the FDH and AFI promoters in the septum is observed in transgenic Arabidopsis but not in Antirrhinum plants. This probably reflects differences in the ontogeny of the ovary septum between the two species. We also show that epidermis-specific FDH-like genes may not be able to efficiently elongate fatty acid chains when misexpressed in seeds.
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Affiliation(s)
- Nadia Efremova
- Max-Planck-Institut für Züchtungsforschung, Carl-von-Linné-Weg 10, 50829 Köln, Germany
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69
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Abstract
Intercellular transport via plasmodesmata controls cell fate decisions in plants, and is of fundamental importance in viral movement, disease resistance, and the spread of RNAi signals. Although plasmodesmata appear to be unique to plant cells, they may have structural and functional similarities to the newly discovered tunneling nanotubes that connect animal cells. Recently, proteins that localize to plasmodesmata have been identified, and a microtubule-associated protein was found to negatively regulate the trafficking of viral movement proteins. Other advances have delivered new insights into the function and molecular nature of plasmodesmata and have shown that protein trafficking through plasmodesmata is developmentally regulated, opening up the possibility that the genetic control of plasmodesmal function will soon be understood.
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Affiliation(s)
- Michelle Lynn Cilia
- Watson School of Biological Sciences, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA.
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70
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Ingram GC. Between the sheets: inter-cell-layer communication in plant development. Philos Trans R Soc Lond B Biol Sci 2004; 359:891-906. [PMID: 15306405 PMCID: PMC1693377 DOI: 10.1098/rstb.2003.1356] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The cells of plant meristems and embryos are arranged in an organized, and sometimes extremely beautiful, layered pattern. This pattern is maintained by the controlled orientation of cell divisions within layers. However, despite this layered structure, cell behaviour during plant development is not lineage dependent, and does not occur in a mosaic fashion. Many studies, both classical and recent, have shown that plant cell identity can be re-specified according to position, allowing plants to show remarkable developmental plasticity. However, the layered structure of meristems and the implications of this during plant development, remain subjects of some speculation. Of particular interest is the question of how cell layers communicate, and how communication between cell layers could allow coordinated developmental processes to take place. Recent research has uncovered several examples both of the molecular mechanisms by which cell layers can communicate, and of how this communication can infringe on developmental processes. A range of examples is used to illustrate the diversity of mechanisms potentially implicated in cell-layer communication during plant development.
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Affiliation(s)
- Gwyneth C Ingram
- Institute of Cell and Molecular Biology, University of Edinburgh, Kings Buildings, Edinburgh EH9 3JR, Scotland, UK.
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71
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Abstract
The evolution of intercellular communication had an important role in the increasing complexity of both multicellular and supracellular organisms. Plasmodesmata, the intercellular organelles of the plant kingdom, establish an effective pathway for local and long-distance signalling. In higher plants, this pathway involves the trafficking of proteins and various forms of RNA that function non-cell-autonomously to affect developmental programmes.
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Affiliation(s)
- William J Lucas
- Department of Plant Biology, University of California, Davis, California 95616, USA.
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72
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Kuijt SJH, Lamers GEM, Rueb S, Scarpella E, Ouwerkerk PBF, Spaink HP, Meijer AH. Different subcellular localization and trafficking properties of KNOX class 1 homeodomain proteins from rice. PLANT MOLECULAR BIOLOGY 2004; 55:781-796. [PMID: 15604716 DOI: 10.1007/s11103-005-1967-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Genes of the KN1-like homeobox (KNOX) class 1 encode transcription factors involved in shoot apical meristem development and maintenance. We studied the subcellular localization of Green Fluorescent Protein-tagged rice KNOX proteins (Oskn1-3) after particle bombardment of onion and rice cells and after transformation of Arabidopsis and rice with constitutive and inducible expression constructs. In all test systems, the three rice KNOX proteins showed nuclear and cytoplasmic localization patterns. However, Oskn1 additionally showed in some cells a distribution over punctae moving randomly in the cytosol. Use of an inducible expression system indicated a nuclear presence of Oskn1 in cells of the shoot apical meristem and post-transcriptional down-regulation in early leaf primordia. Arabidopsis and rice test systems were used to study effects of plant hormones and auxin transport inhibition on KNOX protein localization. Application of GA3 or 1-NAA shifted protein localization completely to the cytoplasm and resulted in loss of the punctae formed by Oskn1. Conversely, NPA application induced a complete nuclear localization of the KNOX proteins. To study intercellular movement of the KNOX proteins we set up a novel co-bombardment assay in which trafficking of untagged KNOX proteins was visualized through the co-trafficking of green fluorescent or blue fluorescent marker proteins. In multiple independent experiments Oskn1 trafficked more extensively to neighboring cells than Oskn2 and Oskn3. Differences in the localization and trafficking properties of Oskn1, Oskn2 and Oskn3 correlate with differences in mRNA localization patterns and functional differences between the rice KNOX genes and their putative orthologues from other species.
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Affiliation(s)
- Suzanne J H Kuijt
- Institute of Biology, Leiden University, Wassenaarseweg 64, 2333 AL, Leiden, the Netherlands
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73
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Abstract
Flowering is one of the most intensively studied processes in plant development. Despite the wide diversity in floral forms, flowers have a simple stereotypical architecture. Flowers develop from florally determined meristems. These small populations of cells proliferate to form the floral organs, including the sterile outer organs, the sepals and petals, and the inner reproductive organs, the stamens and carpels. In the past decade, analyses of key flowering genes have been carried out primarily in Arabidopsis and have provided a foundation for understanding the underlying molecular genetic mechanisms controlling different aspects of floral development. Such studies have illuminated the transcriptional cascades responsible for the regulation of these key genes, as well as how these genes effect their functions. In turn, these studies have resulted in the refinement of the original ideas of how flowers develop and have indicated the gaps in our knowledge that need to be addressed.
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Affiliation(s)
- Moriyah Zik
- Department of Molecular, Cellular and Developmental Biology, Yale University, 266 Whitney Avenue, New Haven, Connecticut 06520, USA
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74
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Heinlein M, Epel BL. Macromolecular Transport and Signaling Through Plasmodesmata. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 235:93-164. [PMID: 15219782 DOI: 10.1016/s0074-7696(04)35003-5] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Plasmodesmata (Pd) are channels in the plant cell wall that in conjunction with associated phloem form an intercellular communication network that supports the cell-to-cell and long-distance trafficking of a wide spectrum of endogenous proteins and ribonucleoprotein complexes. The trafficking of such macromolecules is of importance in the orchestration of non-cell autonomous developmental and physiological processes. Plant viruses encode movement proteins (MPs) that subvert this communication network to facilitate the spread of infection. These viral proteins thus represent excellent experimental keys for exploring the mechanisms involved in intercellular trafficking and communication via Pd.
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Affiliation(s)
- Manfred Heinlein
- Botanical Institute, University of Basel, Hebelstrasse 1, CH-4056 Basel, Switzerland
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75
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76
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Ding B, Itaya A, Qi Y. Symplasmic protein and RNA traffic: regulatory points and regulatory factors. CURRENT OPINION IN PLANT BIOLOGY 2003; 6:596-602. [PMID: 14611959 DOI: 10.1016/j.pbi.2003.09.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Plasmodesmata and the phloem form a cytoplasmic network that permits direct cell-cell communication in plants. This network can mediate the trafficking of selective proteins and RNAs that may have important developmental functions. Recent work has provided evidence that protein and RNA traffic across specific interfaces of this network is regulated in a distinct manner. Progress has been made in identifying potential cellular factors that confer such regulation. These advances should promote further investigations into the mechanisms and functions of protein and RNA traffic using biochemical, cellular, genetic and molecular tools.
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Affiliation(s)
- Biao Ding
- Department of Plant Biology and Plant Biotechnology Center, 207 Rightmire Hall, The Ohio State University, 1060 Carmack Road, Columbus, Ohio 43210, USA.
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77
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Rinne PLH, Schoot CVD. Plasmodesmata at the crossroads between development, dormancy, and defense. ACTA ACUST UNITED AC 2003. [DOI: 10.1139/b03-123] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Plants are frequently exposed to environmental stress and organisms that seek to benefit from their autotrophic nature. To cope with these challenges plants have developed stress-resistance mechanisms, which involve sensing, activation of signal transduction cascades, changes in gene expression, and physiological adjustment. Exposure to one kind of stress often leads to cross-tolerance, that is, resistance to different kinds of stresses. The search for a common underlying mechanism concentrates mostly on changes in cellular physiology and gene expression. We focus on the cross-protective measures that are taken at the level above the single cell. We argue that the controlled alterations in symplasmic permeability that underlie development also play a role in survival and defense strategies. In development, most of the alterations are transient and dynamic, whereas the more persistent alterations function predominantly in dormancy and defense and are under the control of two key enzymes: 1,3-β-D-glucan synthase and 1,3-β-D-glucanase. 1,3-β-D-Glucan synthase functions in the narrowing or closing of plasmodesmata, whereas 1,3-β-D-glucanase counteracts this process. We propose that the closing of symplasmic paths constitutes an unspecific but effective early measure in adaptation and defense, which is accompanied by specific strategies tailored to the various challenges plants face.Key words: cross-adaptation, dormancy sphincter, 1,3-β-D-glucanase, 1,3-β-D-glucan synthase, meristem, overwintering, plasmodesmata, virus movement.
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78
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Schwarz-Sommer Z, Davies B, Hudson A. An everlasting pioneer: the story of Antirrhinum research. Nat Rev Genet 2003; 4:657-66. [PMID: 12897777 DOI: 10.1038/nrg1127] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Despite the tremendous success of Arabidopsis thaliana, no single model can represent the vast range of form that is seen in the approximately 250,000 existing species of flowering plants (angiosperms). Here, we consider the history and future of an alternative angiosperm model--the snapdragon Antirrhinum majus. We ask what made Antirrhinum attractive to the earliest students of variation and inheritance, and how its use led to landmark advances in plant genetics and to our present understanding of plant development. Finally, we show how the wide diversity of Antirrhinum species, combined with classical and molecular genetics--the two traditional strengths of Antirrhinum--provide an opportunity for developmental, evolutionary and ecological approaches. These factors make A. majus an ideal comparative angiosperm.
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79
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Abstract
Chromatin remodeling in plants has usually been discussed in relation to aspects of genome defense such as transgene silencing and the resetting of transposon activity. The role of remodeling in controlling development has been less emphasized, although well established in animal systems. This is because cell fate in plants is often held to be entirely specified on the basis of position, apparently excluding any significant role for cell ancestry and chromatin remodeling. We argue that chromatin remodeling is used to confer mitotically heritable cell fates at late stages in pattern formation. Several examples in which chromatin remodeling factors are used to confer a memory of transient events in plant development are discussed. Because the precise biochemical functions of most remodeling factors are obscure, and little is known of plant chromatin structure, the underlying mechanisms remain poorly understood.
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Affiliation(s)
- Justin Goodrich
- Institute of Cell and Molecular Biology, University of Edinburgh, King's Buildings, Mayfield Road, United Kingdom.
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80
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Rolland-Lagan AG, Bangham JA, Coen E. Growth dynamics underlying petal shape and asymmetry. Nature 2003; 422:161-3. [PMID: 12634785 DOI: 10.1038/nature01443] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2002] [Accepted: 01/20/2003] [Indexed: 11/08/2022]
Abstract
Development commonly involves the generation of complex shapes from simpler ones. One way of following this process is to use landmarks to track the fate of particular points in a developing organ, but this is limited by the time over which it can be monitored. Here we use an alternative method, clonal analysis, whereby dividing cells are genetically marked and their descendants identified visually, to observe the development of Antirrhinum (snapdragon) petals. Clonal analysis has previously been used to estimate growth parameters of leaves and Drosophila wings but these results were not integrated within a dynamic growth model. Here we develop such a model and use it to show that a key aspect of shape--petal asymmetry--in the petal lobe of Antirrhinum depends on the direction of growth rather than regional differences in growth rate. The direction of growth is maintained parallel to the proximodistal axis of the flower, irrespective of changes in shape, implying that long-range signals orient growth along the petal as a whole. Such signals may provide a general mechanism for orienting growth in other growing structures.
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81
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Abstract
A key problem in developmental biology is understanding the origin of morphological innovations. Comparative studies in plants with different leaf morphologies indicate that the developmental pathway defined by KNOTTED1-type homeodomain proteins could be involved in generating different leaf forms. The differential expression of regulatory proteins has emerged as an important factor in driving morphological innovations in the plant kingdom--an idea that is well supported by quantitative trait locus analyses.
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Affiliation(s)
- Miltos Tsiantis
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
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82
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Vincent CA, Carpenter R, Coen ES. Interactions between gene activity and cell layers during floral development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 33:765-774. [PMID: 12609048 DOI: 10.1046/j.1365-313x.2003.01666.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The DEFICIENS (DEF) gene is required for establishing petal and stamen identity in Antirrhinum and is expressed in all three layers of the floral meristem in whorls 2 and 3. Expression of DEF in a subset of meristem layers gives rise to organs with characteristic shapes and cell types, reflecting altered patterns and levels of DEF gene activity. To determine how the contributions of layers and gene activity interact, we exploited a DEF allele which carries a transposon insertion in the MADS box region to generate periclinal chimeras expressing alleles with different activities. By comparing the phenotype, development and expression patterns of these chimeras we show that expression of DEF in L1 makes a major contribution to morphology in whorl 2, irrespective of the allele. By contrast L1 expression is largely unable to rescue whorl 3, possibly because of a non-autonomous inhibitor of DEF activity in this whorl.
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83
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Heinlein M. Plasmodesmata: dynamic regulation and role in macromolecular cell-to-cell signaling. CURRENT OPINION IN PLANT BIOLOGY 2002; 5:543-552. [PMID: 12393018 DOI: 10.1016/s1369-5266(02)00295-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Recent studies have demonstrated the functional significance of intercellular RNA and protein trafficking in plant development, confirming the role of plasmodesmata (PD) in the mediation and control of intercellular communication via macromolecules. Small fluorescent tracer loading techniques and experiments involving the expression of proteins tagged with green fluorescent protein (GFP) have been used to investigate the mechanisms of PD targeting and trafficking, as well as to elucidate the dynamic and structural properties of these channels.
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Affiliation(s)
- Manfred Heinlein
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058, Basel, Switzerland.
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84
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Desvoyes B, Faure-Rabasse S, Chen MH, Park JW, Scholthof HB. A novel plant homeodomain protein interacts in a functionally relevant manner with a virus movement protein. PLANT PHYSIOLOGY 2002; 129:1521-32. [PMID: 12177465 PMCID: PMC166740 DOI: 10.1104/pp.004754] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2002] [Accepted: 03/27/2002] [Indexed: 05/20/2023]
Abstract
Tomato bushy stunt virus and its cell-to-cell movement protein (MP; P22) provide valuable tools to study trafficking of macromolecules through plants. This study shows that wild-type P22 and selected movement-defective P22 amino acid substitution mutants were equivalent for biochemical features commonly associated with MPs (i.e. RNA binding, phosphorylation, and membrane partitioning). This generated the hypothesis that their movement defect was caused by improper interaction between the P22 mutants and one or more host factors. To test this, P22 was used as bait in a yeast (Saccharomyces cerevisiae) two-hybrid screen with a tobacco (Nicotiana tabacum) cDNA library, which identified a new plant homeodomain leucine-zipper protein that reproducibly interacted with P22 but not with various control proteins. These results were confirmed with an independent in vitro binding test. An mRNA for the host protein was detected in plants, and its accumulation was enhanced upon Tomato bushy stunt virus infection of two plant species. The significance of this interaction was further demonstrated by the failure of the homeodomain protein to interact efficiently with two of the well-defined movement-deficient P22 mutants in yeast and in vitro. This is the first report, to our knowledge, that a new plant homeodomain leucine-zipper protein interacts specifically and in a functionally relevant manner with a plant virus MP.
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Affiliation(s)
- Bénédicte Desvoyes
- Department of Plant Pathology and Microbiology, Texas A&M University, 2132 TAMU, College Station, Texas 77843, USA
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85
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Traas J, Vernoux T. The shoot apical meristem: the dynamics of a stable structure. Philos Trans R Soc Lond B Biol Sci 2002; 357:737-47. [PMID: 12079669 PMCID: PMC1692983 DOI: 10.1098/rstb.2002.1091] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The shoot apical meristem (SAM) is a group of proliferating, embryonic-type cells that generates the aerial parts of the plant. SAMs are highly organized and stable structures that can function for years or even centuries. This is in apparent contradiction to the behaviour of their constituent cells, which continuously proliferate and differentiate. To reconcile the dynamic nature of the cells with the stability of the overall system the existence of elaborate signalling networks has been proposed. This is supported by recent work suggesting that the exchange of signals between cells, rather than a rigidly predetermined genetic program, is required for the establishment and functioning of an organized meristem. Together these interactions form a stable network, set up during embryogenesis, that assures the coordination of cell behaviour throughout development. Besides meristem-specific signalling cascades such as the CLAVATA receptor kinase pathway, which controls meristem size, these interactions involve plant hormones. In particular, cytokinins and auxins are implicated in the maintenance of meristem identity and phyllotaxis, respectively.
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Affiliation(s)
- Jan Traas
- INRA, Laboratoire de Biologie Cellulaire, Route de St Cyr, 78026 Versailles cedex, France.
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86
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Clark JI, Coen ES. The cycloidea gene can respond to a common dorsoventral prepattern in Antirrhinum. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2002; 30:639-648. [PMID: 12061896 DOI: 10.1046/j.1365-313x.2002.01310.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Dorsoventral asymmetry in flowers of Antirrhinum depends on expression of the cycloidea gene in dorsal regions of floral meristems. To determine how cycloidea might be regulated we analysed its expression in several contexts. We show that cycloidea is activated shortly after floral induction, and that in addition to flowers, cycloidea can be asymmetrically expressed in shoots, even though these shoots show no marked dorsoventral asymmetry. Shoots expressing cycloidea include secondary branches lying just below the inflorescence, and shoots of floricaula mutants. Asymmetric cycloidea expression may also be observed within organ primordia, such as the sepals of terminal flowers produced by centroradialis mutants. Later expression of cycloidea within flowers can be modified by mutations in organ identity genes. Taken together, the results suggest that cycloidea can respond to a common dorsoventral pre-pattern in the apex and that the specific effects of cycloidea on the flower depend on interactions with floral-specific genes.
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87
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Affiliation(s)
- Xuelin Wu
- Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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88
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Traas J, Doonan JH. Cellular basis of shoot apical meristem development. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 208:161-206. [PMID: 11510568 DOI: 10.1016/s0074-7696(01)08004-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Shoot apical meristems are composed of proliferating, embryonic type cells, that generate tissues and organs throughout the life of the plant. This review covers the cell biology of the higher plant shoot apical meristem (SAM). The first section describes the molecular basis of plant cell growth and division. The genetic mechanisms, that operate in meristem function and the identification of several key regulators of meristem behavior are described in the second section, and intercellular communication and coordination of cellular behavior in the third part. Finally, we discuss some recent results that indicate interaction between the cellular regulators, such as the cell cycle control genes and developmental regulators.
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Affiliation(s)
- J Traas
- Laboratoire de Biologie Cellulaire, Institut National de la Recherche Agronomique, Versailles, France
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89
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Abstract
The shoot apical meristem (SAM) of higher plants functions as a site of continuous organogenesis within which a small pool of pluripotent stem cells replenishes the cells incorporated into lateral organs. This article summarizes recent results demonstrating that the fate of stem cells in Arabidopsis shoot and floral meristems is controlled by overlapping spatial and temporal signaling systems. Stem cell maintenance is an active process requiring constant communication between neighboring groups of SAM cells. Information flows via a ligand-receptor signal transduction pathway, resulting in the formation of a spatial feedback loop that stabilizes the size of the stem cell population. Termination of stem cell activity during flower development is achieved by a temporal feedback loop involving both stem cell maintenance genes and flower patterning genes. These investigations are providing exciting insights into the components and activities of the stem cell regulatory pathway and into the interaction of this pathway with molecular mechanisms that control floral patterning.
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Affiliation(s)
- Jennifer C Fletcher
- Plant and Microbial Biology Department, University of California Berkeley, USDA Plant Gene Expression Center, Albany, California 94710, USA.
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90
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Ueki S, Citovsky V. RNA commutes to work: regulation of plant gene expression by systemically transported RNA molecules. Bioessays 2001; 23:1087-90. [PMID: 11746226 DOI: 10.1002/bies.10027] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Although long-distance movement of endogenous mRNAs in plants is well established, the functional contributions of these transported RNA molecules has remained unclear. In a recent report, Kim et al.2001 showed that systemically transported mRNA is capable of causing phenotypic change in developing tissue. Here, this finding and its significance are reviewed and discussed in detail. In addition, in order to give proper perspective, long-distance transport of other types of RNAs, e.g., RNA elicitors of post-transcriptional gene silencing and RNA genomes of plant viruses, and its possible regulation are discussed.
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Affiliation(s)
- S Ueki
- Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, USA
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91
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Lucas WJ, Yoo BC, Kragler F. RNA as a long-distance information macromolecule in plants. Nat Rev Mol Cell Biol 2001; 2:849-57. [PMID: 11715051 DOI: 10.1038/35099096] [Citation(s) in RCA: 178] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A role for RNA as a non-cell-autonomous information macromolecule is emerging as a new model in biology. Studies on higher plants have shown the operation of cell-to-cell and long-distance communication networks that mediate the selective transport of RNA. The evolution and function of these systems are discussed in terms of an RNA-based signalling network that potentiates control over gene expression at the whole-plant level.
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Affiliation(s)
- W J Lucas
- Section of Plant Biology, Division of Biological Sciences, University of California, One Shields Ave., Davis, California 95616, USA.
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92
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Müller BM, Saedler H, Zachgo S. The MADS-box gene DEFH28 from Antirrhinum is involved in the regulation of floral meristem identity and fruit development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2001; 28:169-79. [PMID: 11722760 DOI: 10.1046/j.1365-313x.2001.01139.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
DEFH28 is a novel MADS-box gene from Antirrhinum majus. Phylogenetic reconstruction indicates that it belongs to the SQUA-subfamily of MADS-box genes. Based on its expression pattern and the phenotype of transgenic plants it is predicted that DEFH28 exerts a dual function during flower development, namely control of meristem identity and fruit development. Firstly, DEFH28 is expressed in the inflorescence apical meristem and might control, together with SQUAMOSA (SQUA), floral meristem identity in Antirrhinum. Also, DEFH28 is sufficient to switch inflorescence shoot meristem to a floral fate in transgenic Arabidopsis thaliana plants. Secondly, DEFH28 is expressed in carpel walls, where it may regulate carpel wall differentiation and fruit maturation. Support for this later role comes from overexpression of DEFH28 throughout the silique in transgenic Arabidopsis plants where it altered the identity of the replum and valve margin cells so that they adopted a valve cell identity. This late aspect of the DEFH28 function is identical to the FRUITFULL (FUL) function of Arabidopsis as demonstrated in gain-of-function plants. FUL, like DEFH28, belongs to the SQUA-subfamily of MADS-box genes. DEFH28 most likely represents the ortholog of FUL. Promoter analysis shows that the control mechanism conferring a carpel wall specific expression has been conserved between Antirrhinum and Arabidopsis during evolution. Although the overall flower development between Antirrhinum and Arabidopsis is very similar, their carpels mature into different types of fruits: capsules and siliques, respectively. Therefore, it is suggested that the role of DEFH28 in control of carpel wall differentiation reflects a conserved molecular mechanism integrated into two very different carpel developmental pathways.
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Affiliation(s)
- B M Müller
- Max-Planck-Institut für Züchtungsforschung, Carl-von-Linné Weg 10, 50829 Köln, Germany
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93
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Nakajima K, Sena G, Nawy T, Benfey PN. Intercellular movement of the putative transcription factor SHR in root patterning. Nature 2001; 413:307-11. [PMID: 11565032 DOI: 10.1038/35095061] [Citation(s) in RCA: 537] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Positional information is pivotal for establishing developmental patterning in plants, but little is known about the underlying signalling mechanisms. The Arabidopsis root radial pattern is generated through stereotyped division of initial cells and the subsequent acquisition of cell fate. short-root (shr) mutants do not undergo the longitudinal cell division of the cortex/endodermis initial daughter cell, resulting in a single cell layer with only cortex attributes. Thus, SHR is necessary for both cell division and endodermis specification. SHR messenger RNA is found exclusively in the stele cells internal to the endodermis and cortex, indicating that it has a non-cell-autonomous mode of action. Here we show that the SHR protein, a putative transcription factor, moves from the stele to a single layer of adjacent cells, where it enters the nucleus. Ectopic expression of SHR driven by the promoter of the downstream gene SCARECROW (SCR) results in autocatalytic reinforcement of SHR signalling, producing altered cell fates and multiplication of cell layers. These results support a model in which SHR protein acts both as a signal from the stele and as an activator of endodermal cell fate and SCR-mediated cell division.
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Affiliation(s)
- K Nakajima
- Department of Biology, New York University, New York, New York 10003, USA
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94
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Kim M, Canio W, Kessler S, Sinha N. Developmental changes due to long-distance movement of a homeobox fusion transcript in tomato. Science 2001; 293:287-9. [PMID: 11452121 DOI: 10.1126/science.1059805] [Citation(s) in RCA: 225] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Long-distance movement of RNA through the phloem is known to occur, but the functional importance of these transported RNAs has remained unclear. Grafting experiments with a naturally occurring dominant gain-of-function leaf mutation in tomato were used to demonstrate long-distance movement of mutant messenger RNA (mRNA) into wild-type scions. The stock-specific pattern of mRNA expression was graft transmissible, indicating that the mRNA accumulation pattern is inherent to the transcript and not attributable to the promoter. The translocated mRNA caused changes in leaf morphology of the wild-type scions, suggesting that the translocated RNA is functional.
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Affiliation(s)
- M Kim
- Section of Plant Biology, Division of Biological Sciences, University of California-Davis, 1 Shields Avenue, Davis, CA 95616, USA
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95
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Zambryski P, Crawford K. Plasmodesmata: gatekeepers for cell-to-cell transport of developmental signals in plants. Annu Rev Cell Dev Biol 2001; 16:393-421. [PMID: 11031242 DOI: 10.1146/annurev.cellbio.16.1.393] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cell walls separate individual plant cells. To enable essential intercellular communication, plants have evolved membrane-lined channels, termed plasmodesmata, that interconnect the cytoplasm between neighboring cells. Historically, plasmodesmata were viewed as facilitating traffic of low-molecular weight growth regulators and nutrients critical to growth. Evidence for macromolecular transport via plasmodesmata was solely based on the exploitation of plasmodesmata by plant viruses during infectious spread. Now plasmodesmata are revealed to transport endogenous proteins, including transcription factors important for development. Two general types of proteins, non-targeted and plasmodesmata-targeted, traffic plasmodesmata channels. Size and subcellular location influence non-targeted protein transportability. Superimposed on cargo-specific parameters, plasmodesmata themselves fluctuate in aperture between closed, open, and dilated. Furthermore, plasmodesmata alter their transport capacity temporally during development and spatially in different regions of the plant. Plasmodesmata are exposed as major gatekeepers of signaling molecules that facilitate or regulate developmental programs, maintain physiological status, and respond to pathogens.
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Affiliation(s)
- P Zambryski
- Department of Plant and Microbial Biology, Koshland Hall, University of California, Berkeley, California 94720, USA.
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96
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Schultz E, Carpenter R, Doyle S, Coen E. The gene fimbriata interacts non-cell autonomously with floral regulatory genes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2001; 25:499-507. [PMID: 11309140 DOI: 10.1046/j.1365-313x.2001.00977.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In Antirrhinum majus, one proposed role of the gene fimbriata (fim) is as a mediator between the floral meristem identify gene floricaula (flo) and floral organ identity genes such as deficiens (def) and plena (ple). The mechanism of fim activity is probably unique as, while the other genes in the hierarchy are thought to be transcription factors, fim is thought to target proteins to a ubiquitin-mediated destruction pathway. Both flo and def have been shown to act non-cell autonomously. We tested the hypotheses that (i) fim acts in a non-cell autonomous manner; and (ii) non-cell autonomy of flo might be through activation and subsequent non-cell autonomous activity of fim. Plants bearing an unstable fim allele were monitored for revertant shoots. Analysis of fim RNA expression in plants derived from revertant shoots, and segregation of revertant phenotype in progeny from revertant plants, indicated that all were periclinal chimeras with wild-type fim expression only in subepidermal layers. Despite the absence of fim in the epidermal layer, expression of downstream genes was normal, suggesting non-cell autonomous activity of fim. Subsequently, we tested the hypothesis that fim is the mediator of flo non-cell autonomy by examining fim expression in flo periclinal chimeras. In these chimeras, fim is activated in cells where flo is not expressed, indicating that fim cannot be the sole mediator of flo non-cell autonomy.
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Affiliation(s)
- E Schultz
- Department of Genetics, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.
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97
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Ehlers K, Kollmann R. Primary and secondary plasmodesmata: structure, origin, and functioning. PROTOPLASMA 2001; 216:1-30. [PMID: 11732191 DOI: 10.1007/bf02680127] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In the multicellular organisms of higher plants, plasmodesmata provide pathways for intimate symplasmic communication between neighboring cells. The arguments summarized in the present review demonstrate that plasmodesmata are diverse and highly dynamic structures. Differences in the plasmodesmal origin and modifications of the plasmodesmal structure and functioning at the various cell interfaces are the basic means which give rise to a complicated and flexibile symplasmic network. This complex communication system is discussed to serve a significant role in the coordinated development and in the concerted physiological functioning of the cells within the plant tissues, organs, and organisms.
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Affiliation(s)
- K Ehlers
- Institut für Allgemeine Botanik und Pflanzenphysiologie, Justus-Liebig-Universität Giessen, Senckenbergstrasse 17, D-35390 Giessen, Federal Republic of Germany.
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98
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Jenik PD, Irish VF. The Arabidopsis floral homeotic gene APETALA3 differentially regulates intercellular signaling required for petal and stamen development. Development 2001; 128:13-23. [PMID: 11092807 DOI: 10.1242/dev.128.1.13] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cell-cell signaling is crucial for the coordination of cell division and differentiation during plant organogenesis. We have developed a novel mosaic analysis method for Arabidopsis, based on the maize Ac/Ds transposable element system, to assess the requirements of individual genes in intercellular signaling. Using this strategy, we have shown that the floral homeotic APETALA3 (AP3) gene has distinct roles in regulating intercellular signaling in different tissues. In petals, AP3 acts primarily in a cell-autonomous fashion to regulate cell type differentiation, but its function is also required in a non-cell-autonomous fashion to regulate organ shape. In contrast, AP3-regulated intercellular interactions are required for conferring both cell type identity and organ shape and size in the stamens. Using antibodies raised against AP3, we have shown that the AP3 protein does not traffic between cells. These observations imply that AP3 acts by differentially regulating the production of intercellular signals in a whorl-specific manner.
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Affiliation(s)
- P D Jenik
- Department of Molecular, Cellular and Developmental Biology, PO Box 208104, Yale University, New Haven, CT 06520, USA
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99
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Boyko V, Ferralli J, Ashby J, Schellenbaum P, Heinlein M. Function of microtubules in intercellular transport of plant virus RNA. Nat Cell Biol 2000; 2:826-32. [PMID: 11056538 DOI: 10.1038/35041072] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cell-to-cell progression of tobacco mosaic virus (TMV) infection in plants depends on virus-encoded movement protein (MP). Here we show that a conserved sequence motif in tobamovirus MPs shares similarity with a region in tubulins that is proposed to mediate lateral contacts between microtubule protofilaments. Point mutations in this motif confer temperature sensitivity to microtubule association and viral-RNA intercellular-transport functions of the protein, indicating that MP-interacting microtubules are functionally involved in the transport of vRNA to plasmodesmata. Moreover, we show that MP interacts with microtubule-nucleation sites. Together, our results indicate that MP may mimic tubulin assembly surfaces to propel vRNA transport by a dynamic process that is driven by microtubule polymerization.
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Affiliation(s)
- V Boyko
- Friedrich Miescher-Institute, Maulbeerstrasse 66, CH-4058 Basel, Switzerland
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100
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Sheppard LA, Brunner AM, Krutovskii KV, Rottmann WH, Skinner JS, Vollmer SS, Strauss SH. A DEFICIENS homolog from the dioecious tree black cottonwood is expressed in female and male floral meristems of the two-whorled, unisexual flowers. PLANT PHYSIOLOGY 2000; 124:627-640. [PMID: 11027713 PMCID: PMC59169 DOI: 10.1104/pp.124.2.627] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2000] [Accepted: 07/03/2000] [Indexed: 05/23/2023]
Abstract
We isolated PTD, a member of the DEFICIENS (DEF) family of MADS box transcription factors, from the dioecious tree, black cottonwood (Populus trichocarpa). In females, in situ hybridization experiments showed that PTD mRNA was first detectable in cells on the flanks of the inflorescence meristem, before differentiation of individual flowers was visually detectable. In males, the onset of PTD expression was delayed until after individual flower differentiation had begun and floral meristems were developing. Although PTD was initially expressed throughout the inner whorl meristem in female and male flowers, its spatial expression pattern became sex-specific as reproductive primordia began to form. PTD expression was maintained in stamen primordia, but excluded from carpel primordia, as well as vegetative tissues. Although PTD is phylogenetically most closely related to the largely uncharacterized TM6 subfamily of the DEF/APETELA3(AP3)/TM6 group, its spatio-temporal expression patterns are more similar to that of DEF and AP3 than to other members of the TM6 subfamily.
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Affiliation(s)
- L A Sheppard
- Genetics Program, Oregon State University, Corvallis, Oregon 97331-5752, USA
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