151
|
Gu SH. Autocrine activation of DNA synthesis in prothoracic gland cells of the silkworm, Bombyx mori. JOURNAL OF INSECT PHYSIOLOGY 2006; 52:136-45. [PMID: 16266718 DOI: 10.1016/j.jinsphys.2005.09.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2005] [Revised: 09/27/2005] [Accepted: 09/27/2005] [Indexed: 05/05/2023]
Abstract
Autocrine activation of DNA synthesis in prothoracic gland cells in last instar larvae of the silkworm, Bombyx mori, was studied using both a long-term in vitro organ culture system and immunocytochemical labeling with 5-bromo-2'-deoxyuridine (BrdU). When prothoracic glands were incubated in a small volume of culture medium (10 microl/gland), the numbers of DNA-synthesizing cells per gland increased significantly, and DNA synthesis was stimulated less by hemolymph, as compared with glands incubated in a large volume (50 microl/gland). Moreover, glands cultured in groups (6 glands per group in a 50-microl drop) also resulted in much higher levels of DNA synthesis than those cultured individually in a 50-microl drop. The mechanism by which alternation of the volume of the incubation medium results in changes in the levels of DNA synthesis was further examined. When prothoracic glands were incubated in medium (50-microl drop per gland) that was preconditioned with glands (in a 10-microl drop individually), a dramatic increase in DNA synthesis activity was also observed, indicating that prothoracic glands may release a factor that stimulates their own DNA synthesis. The growth-promoting factor was further characterized and it was found that the factor is heat stable, and its molecular weight was estimated to be between 1,000 and 3,000 Da. Moreover, the factor also stimulated corpus allatum cell DNA synthesis in vitro. Injection of concentrated putative growth-promoting factor into day 4 last instar-ligated larvae greatly increased cell DNA synthesis of the prothoracic glands, indicating the in vivo function of the present autocrine factor.
Collapse
Affiliation(s)
- Shi-Hong Gu
- Department of Zoology, National Museum of Natural Science, 1 Kuan Chien Road, Taichung, Taiwan, ROC.
| |
Collapse
|
152
|
González-Sama A, de la Peña TC, Kevei Z, Mergaert P, Lucas MM, de Felipe MR, Kondorosi E, Pueyo JJ. Nuclear DNA endoreduplication and expression of the mitotic inhibitor Ccs52 associated to determinate and lupinoid nodule organogenesis. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:173-80. [PMID: 16529379 DOI: 10.1094/mpmi-19-0173] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Lotus japonicus determinate nodules differ greatly from indeterminate nodules in their organogenesis and morphological characteristics, whereas Lupinus albus lupinoid nodules share features of determinate and indeterminate nodules. The mitotic inhibitor Ccs52A is essential for endoreduplication and ploidy-dependent cell enlargement during symbiotic cell differentiation in Medicago truncatula indeterminate nodules. ccs52A homolog genes were isolated from lupin and lotus nodules; the deduced Ccs52A proteins showed high sequence similarity with other Cdh-1-type activators of the anaphase-promoting complex and were grouped with A-type Ccs52 proteins from different plants. In lupin, ccs52A expression was restricted to the earlier stages of nodule development, whereas ccs52A transcripts accumulated in lotus nodule primordia and, to a lesser extent, in mature nodules. Nodule development in Lupinus albus involved a progressive increase in nuclear and cellular size and ploidy level; similarly, Lotus japonicus nodules contained polyploid nuclei and enlarged cells in the infected zone. Nevertheless, in situ hybridization experiments showed the highest ccs52A expression in the inner cortex cells of the lupin nodule primordium, probably associated to the increased size of these cells in mature nodules. In view of our results, Ccs52A-mediated endoreduplication appears to be a universal mechanism required for nodule cell differentiation during the establishment of nitrogen-fixing symbioses.
Collapse
Affiliation(s)
- Alfonso González-Sama
- Institut des Sciences du Vegetal, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2355, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France
| | | | | | | | | | | | | | | |
Collapse
|
153
|
Abstract
Two main attempts have been suggested for the biological significance of endopolyploidy: (i) provision of high DNA amounts to support high synthetic demands in certain cells and (ii) compensation for a lack of nuclear DNA in species with small genomes. However, in seed plants, the positive correlation between DNA content and cell volume of endopolyploid cells suggests other possibilities. Cell size paralleled by the endopolyploidy level has an impact on growth and development. Endopolyploidy levels in turn are characteristic for a given species and even families, reflecting the adaptation to certain habitats during phylogeny. Furthermore, endopolyploidy levels vary to some degree between individuals of one species in response to different environmental conditions. In addition, endopolyploidy differs between different tissues suggests that a certain cell size is advantageous for a given cell function. This article reviews these findings and discusses more conclusive possible functions of endopolyploidy.
Collapse
Affiliation(s)
- Martin Barow
- Institute of Plants Genetics and Crop Plant Research Gatersleben, Germany.
| |
Collapse
|
154
|
Abstract
Polyploids - organisms that have multiple sets of chromosomes - are common in certain plant and animal taxa, and can be surprisingly stable. The evidence that has emerged from genome analyses also indicates that many other eukaryotic genomes have a polyploid ancestry, suggesting that both humans and most other eukaryotes have either benefited from or endured polyploidy. Studies of polyploids soon after their formation have revealed genetic and epigenetic interactions between redundant genes. These interactions can be related to the phenotypes and evolutionary fates of polyploids. Here, I consider the advantages and challenges of polyploidy, and its evolutionary potential.
Collapse
Affiliation(s)
- Luca Comai
- Department of Biology, Box 355325, University of Washington, Seattle, Washington 98195, USA.
| |
Collapse
|
155
|
Cheniclet C, Rong WY, Causse M, Frangne N, Bolling L, Carde JP, Renaudin JP. Cell expansion and endoreduplication show a large genetic variability in pericarp and contribute strongly to tomato fruit growth. PLANT PHYSIOLOGY 2005; 139:1984-94. [PMID: 16306145 PMCID: PMC1310575 DOI: 10.1104/pp.105.068767] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Postanthesis growth of tomato (Solanum lycopersicon) as of many types of fruit relies on cell division and cell expansion, so that some of the largest cells to be found in plants occur in fleshy fruit. Endoreduplication is known to occur in such materials, which suggests its involvement in cell expansion, although no data have demonstrated this hypothesis as yet. We have analyzed pattern formation, cell size, and ploidy in tomato fruit pericarp. A first set of data was collected in one cherry tomato line throughout fruit development. A second set of data was obtained from 20 tomato lines displaying a large weight range in fruit, which were compared as ovaries at anthesis and as fully grown fruit at breaker stage. A remarkable conservation of pericarp pattern, including cell layer number and cell size, is observed in all of the 20 tomato lines at anthesis, whereas large variations of growth occur afterward. A strong, positive correlation, combining development and genetic diversity, is demonstrated between mean cell size and ploidy, which holds for mean cell diameters from 10 to 350 microm (i.e. a 32,000-times volume variation) and for mean ploidy levels from 3 to 80 C. Fruit weight appears also significantly correlated with cell size and ploidy. These data provide a framework of pericarp patterning and growth. They strongly suggest the quantitative importance of polyploidy-associated cell expansion as a determinant of fruit weight in tomato.
Collapse
Affiliation(s)
- Catherine Cheniclet
- Unité Mixte de Recherche 619 Physiologie et Biotechnologies Végétales, Institut National de la Recherche Agronomique, Université Bordeaux 1, Université Victor Segalen Bordeaux 2, 33883 Villenave d'Ornon, France
| | | | | | | | | | | | | |
Collapse
|
156
|
Sugiyama SI. Polyploidy and cellular mechanisms changing leaf size: comparison of diploid and autotetraploid populations in two species of Lolium. ANNALS OF BOTANY 2005; 96:931-8. [PMID: 16100224 PMCID: PMC4247059 DOI: 10.1093/aob/mci245] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
BACKGROUND AND AIMS Growth and development of plant organs, including leaves, depend on cell division and expansion. Leaf size is increased by greater cell ploidy, but the mechanism of this effect is poorly understood. Therefore, in this study, the role of cell division and expansion in the increase of leaf size caused by polyploidy was examined by comparing various cell parameters of the mesophyll layer of developing leaves of diploid and autotetraploid cultivars of two grass species, Lolium perenne and L. multiflorum. METHODS Three cultivars of each ploidy level of both species were grown under pot conditions in a controlled growth chamber, and leaf elongation rate and the cell length profile at the leaf base were measured on six plants in each cultivar. Cell parameters related to division and elongation activities were calculated by a kinematic method. KEY RESULTS Tetraploid cultivars had faster leaf elongation rates than did diploid cultivars in both species, resulting in longer leaves, mainly due to their longer mature cells. Epidermal and mesophyll cells differed 20-fold in length, but were both greater in the tetraploid cultivars of both species. The increase in cell length of the tetraploid cultivars was caused by a faster cell elongation rate, not by a longer period of cell elongation. There were no significant differences between cell division parameters, such as cell production rate and cell cycle time, in the diploid and tetraploid cultivars. CONCLUSION The results demonstrated clearly that polyploidy increases leaf size mainly by increasing the cell elongation rate, but not the duration of the period of elongation, and thus increases final cell size.
Collapse
Affiliation(s)
- Shu-Ichi Sugiyama
- Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan.
| |
Collapse
|
157
|
Diaz-Trivino S, del Mar Castellano M, de la Paz Sanchez M, Ramirez-Parra E, Desvoyes B, Gutierrez C. The genes encoding Arabidopsis ORC subunits are E2F targets and the two ORC1 genes are differently expressed in proliferating and endoreplicating cells. Nucleic Acids Res 2005; 33:5404-14. [PMID: 16179646 PMCID: PMC1236721 DOI: 10.1093/nar/gki854] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Initiation of eukaryotic DNA replication depends on the function of pre-replication complexes (pre-RC), one of its key component being the six subunits origin recognition complex (ORC). In spite of a significant degree of conservation among ORC proteins from different eukaryotic sources, the regulation of their availability varies considerably in different model systems and cell types. Here, we show that the six ORC genes of Arabidopsis thaliana are regulated at the transcriptional level during cell cycle and development. We found that Arabidopsis ORC genes, except AtORC5, contain binding sites for the E2F family of transcription factors. Expression of AtORC genes containing E2F binding sites peaks at the G1/S-phase. Analysis of AtORC gene expression in plants with reduced E2F activity, obtained by expressing a dominant negative version of DP, the E2F heterodimerization partner, and with increased E2F activity, obtained by inactivation of the retinoblastoma protein, led us to conclude that all AtORC genes, except AtORC5 are E2F targets. Interestingly, Arabidopsis contains two AtORC1 (a and b) genes, highly conserved at the amino acid level but with unrelated promoter sequences. AtORC1b expression is restricted to proliferating cells. However, AtORC1a is preferentially expressed in endoreplicating cells based on our analysis in endoreplicating tissues and in a mutant with altered endocycle pattern. This suggests a differential expression of the two ORC1 genes in Arabidopsis.
Collapse
Affiliation(s)
| | | | | | | | | | - Crisanto Gutierrez
- To whom correspondence should be addressed. Tel: +34 91 497 8430; Fax: +34 91 4974799;
| |
Collapse
|
158
|
Abstract
Cell-cycle regulation plays a crucial role in organogenesis, morphogenesis, growth and differentiation and conceptually offers a means to design a next generation of crop plants that outperform traditionally bred ones. However, cell-cycle regulation involves a large, highly redundant, set of genes, which complicates unravelling of function in the context of a higher plant. Nevertheless, ten years of molecular cell-cycle research, primarily in the model plant Arabidopsis, have demonstrated its potential for altering plant development.
Collapse
Affiliation(s)
- Gerrit T S Beemster
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology (VIB)/Ghent University, Technologiepark 927, Ghent, Belgium
| | | | | |
Collapse
|
159
|
Abstract
Size control has been a topic of interest to cell biologists for over a century, but insights into cell size control mechanisms have until recently been relatively sparse. Determining whether cells have a size measurement mechanism and how it might operate has proven difficult. The nucleocytoplasmic ratio is one of the few conserved features of size control but little is know about how it is measured. Models where growth and division can be uncoupled have been underexploited, but have considerable potential for gaining insights into the contribution of the nucleocytoplasmic ratio to cell size regulation.
Collapse
Affiliation(s)
- James G Umen
- Plant Biology Laboratory, The Salk Institute, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA.
| |
Collapse
|
160
|
Abstract
Plant genome projects have revealed that both the cell-cycle components and the overall cell-cycle architecture are highly evolutionarily conserved. In addition to the temporal and spatial regulation of cell-cycle progression in individual cells, multicellularity has imposed extra layers of complexity that impinge on the balance of cell proliferation and growth, differentiation and organogenesis. In contrast to animals, organogenesis in plants is a postembryonic and continuous process. Differentiated plant cells can revert to a pluripotent state, proliferate and transdifferentiate. This unique potential is strikingly illustrated by the ability of certain cells to produce a mass of undifferentiated cells or a fully totipotent embryo, which can regenerate mature plants. Conversely, plant cells are highly resistant to oncogenic transformation. This review discusses the role that cell-cycle regulators may have at the interface between cell division and differentiation, and in the context of the high plasticity of plant cells.
Collapse
Affiliation(s)
- Crisanto Gutierrez
- Centro de Biologia Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
| |
Collapse
|
161
|
Fusconi A, Lingua G, Trotta A, Berta G. Effects of arbuscular mycorrhizal colonization and phosphorus application on nuclear ploidy in Allium porrum plants. MYCORRHIZA 2005; 15:313-321. [PMID: 15565274 DOI: 10.1007/s00572-004-0338-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2004] [Accepted: 10/15/2004] [Indexed: 05/24/2023]
Abstract
Arbuscular mycorrhizal (AM) colonization can strongly affect the plant cell nucleus, causing displacement from the periphery to the center of the cell, hypertrophy and polyploidization. The hypertrophy response has been shown in a variety of AM plants whilst polyploidization has been reported only in Lycopersicon esculentum, a multiploid species with a small genome. In order to determine whether polyploidization is a general plant response to AM colonization, analyses were performed on Allium porrum, a plant with a large genome, which is much less subject to polyploidization than L. esculentum. The ploidy status of leaves, complete root systems and four zones of the adventitious roots was investigated in relation to phosphorus content, AM colonization and root differentiation in A. porrum plants grown under two different regimes of phosphate nutrition in order to distinguish direct effects of the fungus from those of improved nutrition. Results showed the presence of two nuclear populations (2C and 4C) in all treatments and samples. Linear regression analyses suggested a general negative correlation between phosphorus content and the proportion of 2C nuclei. The percentage of 2C nuclei (and consequently that of 4C nuclei), was also influenced by AM colonization, differentiation and ageing of the root cells, which resulted in earlier occurrence, in time and space, of polyploid nuclei.
Collapse
Affiliation(s)
- Anna Fusconi
- Dipartimento di Biologia Vegetale, Università di Torino, Viale Mattioli 25, 10125 Torino, Italy.
| | | | | | | |
Collapse
|
162
|
Verkest A, Manes CLDO, Vercruysse S, Maes S, Van Der Schueren E, Beeckman T, Genschik P, Kuiper M, Inzé D, De Veylder L. The cyclin-dependent kinase inhibitor KRP2 controls the onset of the endoreduplication cycle during Arabidopsis leaf development through inhibition of mitotic CDKA;1 kinase complexes. THE PLANT CELL 2005; 17:1723-36. [PMID: 15863515 PMCID: PMC1143072 DOI: 10.1105/tpc.105.032383] [Citation(s) in RCA: 202] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Exit from the mitotic cell cycle and initiation of cell differentiation frequently coincides with the onset of endoreduplication, a modified cell cycle during which DNA continues to be duplicated in the absence of mitosis. Although the mitotic cell cycle and the endoreduplication cycle share much of the same machinery, the regulatory mechanisms controlling the transition between both cycles remain poorly understood. We show that the A-type cyclin-dependent kinase CDKA;1 and its specific inhibitor, the Kip-related protein, KRP2 regulate the mitosis-to-endocycle transition during Arabidopsis thaliana leaf development. Constitutive overexpression of KRP2 slightly above its endogenous level only inhibited the mitotic cell cycle-specific CDKA;1 kinase complexes, whereas the endoreduplication cycle-specific CDKA;1 complexes were unaffected, resulting in an increase in the DNA ploidy level. An identical effect on the endoreduplication cycle could be observed by overexpressing KRP2 exclusively in mitotically dividing cells. In agreement with a role for KRP2 as activator of the mitosis-to-endocycle transition, KRP2 protein levels were more abundant in endoreduplicating than in mitotically dividing tissues. We illustrate that KRP2 protein abundance is regulated posttranscriptionally through CDK phosphorylation and proteasomal degradation. KRP2 phosphorylation by the mitotic cell cycle-specific CDKB1;1 kinase suggests a mechanism in which CDKB1;1 controls the level of CDKA;1 activity through regulating KRP2 protein abundance. In accordance with this model, KRP2 protein levels increased in plants with reduced CDKB1;1 activity. Moreover, the proposed model allowed a dynamical simulation of the in vivo observations, validating the sufficiency of the regulatory interactions between CDKA;1, KRP2, and CDKB1;1 in fine-tuning the mitosis-to-endocycle transition.
Collapse
Affiliation(s)
- Aurine Verkest
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent University, B-9052 Gent, Belgium
| | | | | | | | | | | | | | | | | | | |
Collapse
|
163
|
Weinl C, Marquardt S, Kuijt SJH, Nowack MK, Jakoby MJ, Hülskamp M, Schnittger A. Novel functions of plant cyclin-dependent kinase inhibitors, ICK1/KRP1, can act non-cell-autonomously and inhibit entry into mitosis. THE PLANT CELL 2005; 17:1704-22. [PMID: 15749764 PMCID: PMC1143071 DOI: 10.1105/tpc.104.030486] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 02/04/2005] [Accepted: 02/04/2005] [Indexed: 05/18/2023]
Abstract
In animals, cyclin-dependent kinase inhibitors (CKIs) are important regulators of cell cycle progression. Recently, putative CKIs were also identified in plants, and in previous studies, Arabidopsis thaliana plants misexpressing CKIs were found to have reduced endoreplication levels and decreased numbers of cells consistent with a function of CKIs in blocking the G1-S cell cycle transition. Here, we demonstrate that at least one inhibitor from Arabidopsis, ICK1/KRP1, can also block entry into mitosis but allows S-phase progression causing endoreplication. Our data suggest that plant CKIs act in a concentration-dependent manner and have an important function in cell proliferation as well as in cell cycle exit and in turning from a mitotic to an endoreplicating cell cycle mode. Endoreplication is usually associated with terminal differentiation; we observed, however, that cell fate specification proceeded independently from ICK1/KRP1-induced endoreplication. Strikingly, we found that endoreplicated cells were able to reenter mitosis, emphasizing the high degree of flexibility of plant cells during development. Moreover, we show that in contrast with animal CDK inhibitors, ICK1/KRP1 can move between cells. On the one hand, this challenges plant cell cycle control with keeping CKIs locally controlled, and on the other hand this provides a possibility of linking cell cycle control in single cells with the supracellular organization of a tissue or an organ.
Collapse
Affiliation(s)
- Christina Weinl
- Unigruppe am Max-Planck-Institut für Züchtungsforschung, Lehrstuhl für Botanik III, Max-Delbrück-Laboratorium, 50829 Köln, Germany
| | | | | | | | | | | | | |
Collapse
|
164
|
Raynaud C, Perennes C, Reuzeau C, Catrice O, Brown S, Bergounioux C. Cell and plastid division are coordinated through the prereplication factor AtCDT1. Proc Natl Acad Sci U S A 2005; 102:8216-21. [PMID: 15928083 PMCID: PMC1149429 DOI: 10.1073/pnas.0502564102] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The cell division cycle involves nuclear and cytoplasmic events, namely organelle multiplication and distribution between the daughter cells. Until now, plastid and plant cell division have been considered as independent processes because they can be uncoupled. Here, down-regulation of AtCDT1a and AtCDT1b, members of the prereplication complex, is shown to alter both nuclear DNA replication and plastid division in Arabidopsis thaliana. These data constitute molecular evidence for relationships between the cell-cycle and plastid division. Moreover, the severe developmental defects observed in AtCDT1-RNA interference (RNAi) plants underline the importance of coordinated cell and organelle division for plant growth and morphogenesis.
Collapse
Affiliation(s)
- Cécile Raynaud
- Institut de Biotechnologie des Plantes, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8618, Bâtiment 630, Université Paris XI, 91405 Orsay, France.
| | | | | | | | | | | |
Collapse
|
165
|
Rolletschek H, Koch K, Wobus U, Borisjuk L. Positional cues for the starch/lipid balance in maize kernels and resource partitioning to the embryo. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 42:69-83. [PMID: 15773854 DOI: 10.1111/j.1365-313x.2005.02352.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
This study tests the hypotheses that in vivo oxygen levels inside developing maize grains locally affect assimilate partitioning and ATP distribution within the kernel. These questions were addressed through combined topographical analysis (O2- and ATP-mapping), metabolite profiling, and isotope flux analysis. Internal and external oxygen levels were also experimentally altered. Under ambient conditions, mean O2 concentration immediately inside starchy endosperm dropped to only 1.4% of atmospheric saturation (approximately 3.8 microm), but was 10-fold higher in the oil-storing embryo. Increasing the O2 supply to intact kernels stimulated their O2 demand, shifted ATP localization within the kernel, and elevated their ATP/ADP ratio. Enhanced O2 availability also increased steady-state levels of glycolytic intermediates and those of the citric acid cycle, as well as some related pools of free amino acids. Subsequent analyses indicated that starch formation within endosperm, but not lipid biosynthesis within embryo, was adapted to the endogenous low oxygen. Increasing the O2 supply did not change ADP-glucose levels, activity of ADP-glucose pyrophosphorylase, 13C-labeling of ADP-glucose, or flux of 14C-sucrose into starch. In contrast, enhanced O2 availability increased 14C-label uptake into the embryo, 13C-labeling of acetyl-coenzyme A, and finally 14C-incorporation into lipids. Lipid accumulation in embryo appeared highest in regions with higher ATP. Consistent with labeling data, a decrease in O2 supply most strongly affected the embryo, whereas rising O2 levels expanded ATP-rich zones toward the starch-storing endosperm and the scutellar part of embryo. The latter might be responsible for higher 14C-label uptake into the embryo and flux toward lipid. Collectively, data indicate that the in vivo oxygen distribution in maize kernels markedly affects ATP gradients, metabolite levels, and favors assimilate partitioning toward starch within the O2-depleted endosperm. Clear advantages are thus evident for peripheral localization of the protein and lipid storing structures in maize kernels.
Collapse
Affiliation(s)
- Hardy Rolletschek
- Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK), Corrensstr. 3, 06466 Gatersleben, Germany
| | | | | | | |
Collapse
|
166
|
Zanet J, Pibre S, Jacquet C, Ramirez A, de Alborán IM, Gandarillas A. Endogenous Myc controls mammalian epidermal cell size, hyperproliferation, endoreplication and stem cell amplification. J Cell Sci 2005; 118:1693-704. [PMID: 15797928 DOI: 10.1242/jcs.02298] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The transcription factor Myc (c-Myc) plays an important role in cell growth and cell death, yet its physiological function remains unclear. Ectopic activation of Myc has been recently suggested to regulate cell mass, and Drosophila dmyc controls cellular growth and size independently of cell division. By contrast, it has been proposed that in mammals Myc controls cell division and cell number. To gain insights into this debate we have specifically knocked out Myc in epidermis. Myc epidermal knockout mice are viable and their keratinocytes continue to cycle, but they display severe skin defects. The skin is tight and fragile, tears off in areas of mechanical friction and displays impaired wound healing. Steady-state epidermis is thinner, with loss of the proliferative compartment and premature differentiation. Remarkably, keratinocyte cell size, growth and endoreplication are reduced, and stem cell amplification is compromised. The results provide new and direct evidence for a role for endogenous Myc in cellular growth that is required for hyperproliferative cycles and tissue homeostasis.
Collapse
Affiliation(s)
- Jennifer Zanet
- Institut de Génétique Moléculaire de Montpellier, CNRS/UMII, Montpellier, France
| | | | | | | | | | | |
Collapse
|
167
|
Lamboursain L, Jolicoeur M. Determination of cell concentration in a plant cell suspension using a fluorescence microplate reader. PLANT CELL REPORTS 2005; 23:665-672. [PMID: 15747158 DOI: 10.1007/s00299-004-0899-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2004] [Revised: 10/18/2004] [Accepted: 10/26/2004] [Indexed: 05/24/2023]
Abstract
Microscopic counting of plant cells is a very tedious and time-consuming process and is therefore seldom used to evaluate plant cell number on a routine basis. This study describes a fast and simple method to evaluate cell concentration in a plant cell suspension using a fluorescence microplate reader. Eschscholtzia californica cells were fixed in a mix of methanol and acetic acid (3:1) and stained with a fluorescent DNA binding dye (Hoechst 33258). Readings were done in a fluorescence microplate reader at 360/465 nm. Specific binding of the dye to double-stranded DNA was significantly favored over unspecific binding when 1.0 M Tris buffer at pH 7.5 containing 1.0 M NaCl and 75 microg ml(-1) of Hoechst 33258 was used. Fluorescence readings must be done between 4 min and 12 min following the addition of the staining solution to the sample. The microplate counting method provides a convenient, rapid and sensitive procedure for determining the cell concentration in plant cell suspensions. The assay has a linear detection range from 0.2 x 10(6) cells to 10.0 x 10(6) cells per milliliter (actual concentration in the tested cell suspension). The time needed to perform the microplate counting was 10% of that needed for the microscopic enumeration. However, this microplate counting method can only be used on genetically stable cell lines and on asynchronous cell suspensions.
Collapse
Affiliation(s)
- Laurence Lamboursain
- Canada Research Chair on the Development of Metabolic Engineering Tools, Bio-P2 Research Unit, Department of Chemical Engineering, Ecole Polytechnique de Montréal, P.O. Box 6079, Station Centre-ville, Montreal, Quebec, Canada, H3C 3A7
| | | |
Collapse
|
168
|
Yang M, Loh CS. Systemic endopolyploidy in Spathoglottis plicata (Orchidaceae) development. BMC Cell Biol 2004; 5:33. [PMID: 15341672 PMCID: PMC516767 DOI: 10.1186/1471-2121-5-33] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2004] [Accepted: 09/01/2004] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Endopolyploidy is developmentally regulated. Presence of endopolyploidy as a result of endoreduplication has been characterized in insects, mammals and plants. The family Orchidaceae is the largest among the flowering plants. Many of the members of the orchid family are commercially micropropagated. Very little has been done to characterize the ploidy variation in different tissues of the orchid plants during development. RESULTS The DNA contents and ploidy level of nuclei extracted from various tissues of a tropical terrestrial orchid Spathoglottis plicata were examined by flow cytometry. Sepals, petals and ovary tissues were found to have only a 2C (C, DNA content of the unreplicated haploid chromosome complement) peak. Columns, floral pedicels of newly open flowers and growing flower stems were observed to have an endopolyploid 8C peak in addition to 2C and 4C peaks. In developing floral pedicels, four peaks were observed for 2C, 4C, 8C and 16C. In root tips, there were 2C, 4C and 8C peaks. But in the root tissues at the region with root hairs, only a 2C peak was observed. Nuclei extracted from young leaves shown three peaks for 2C, 4C and 8C. A similar pattern was found in the vegetative tissues of both greenhouse-grown plants and tissue-cultured plantlets. In mature leaves, a different pattern of ploidy level was found at different parts of the leaves. In the leaf tips and middle parts, there were 2C and 4C peaks. Only at the basal part of the leaves, there were three peaks for 2C, 4C and 8C. CONCLUSIONS Systemic variation of cellular endopolyploidy in different tissues during growth and development of Spathoglottis plicata from field-grown plants and in vitro cultures was identified. The implication of the findings was discussed.
Collapse
Affiliation(s)
- Maocheng Yang
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Chiang Shiong Loh
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543
| |
Collapse
|
169
|
|
170
|
Kondorosi E, Kondorosi A. Endoreduplication and activation of the anaphase-promoting complex during symbiotic cell development. FEBS Lett 2004; 567:152-7. [PMID: 15165909 DOI: 10.1016/j.febslet.2004.04.075] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2004] [Accepted: 04/19/2004] [Indexed: 11/15/2022]
Abstract
Postembryonic development of plant organs requires a constant interplay between the cell cycle and the developmental programs. Upon endo- and exogenous signals, plant cells can enter, exit or modify the cell cycle. Alteration of mitotic cycles to endoreduplication cycles, where the genome is duplicated without mitosis, is common in plants and may play a role in cell differentiation. The switch from the mitotic to endocycles is regulated by Ccs52A, a plant orthologue of the yeast and animal Cdhl proteins, acting as substrate-specific activator of the anaphase-promoting complex E3 ubiquitin ligase. Here, several aspects of endoreduplication are discussed with special attention on nitrogen-fixing nodule development where endoreduplication is an integral part of symbiotic cell differentiation.
Collapse
Affiliation(s)
- Eva Kondorosi
- Institut des Sciences du Végétal, CNRS UPR 2355, Avenue de la Terrasse, 91198 Gif-sur- Yvette, France
| | | |
Collapse
|
171
|
Matsunaga S, Uchida W, Kawano S. Sex-Specific Cell Division during Development of Unisexual Flowers in the Dioecious Plant Silene latifolia. ACTA ACUST UNITED AC 2004; 45:795-802. [PMID: 15215515 DOI: 10.1093/pcp/pch081] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
We analyzed cell division patterns during the differentiation of unisexual flowers of the dioecious plant Silene latifolia using in situ hybridization with histone H4 and cyclin A1 genes. The gene expression patterns indicated that the activation of cell divisions in whorls 3 and 4 was reversed in young male and female flower buds. During maturation of flower buds, a remarkable reduction in cell division activity occurred in the male gynoecium primordium and female stamen primordia. Our analyses showed that differential activation and reduction of cell division strongly correlated with sex-specific promotion and cessation in the sex differentiation of unisexual flowers.
Collapse
Affiliation(s)
- Sachihiro Matsunaga
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 277-8562 Japan.
| | | | | |
Collapse
|
172
|
Storchova Z, Pellman D. From polyploidy to aneuploidy, genome instability and cancer. Nat Rev Mol Cell Biol 2004; 5:45-54. [PMID: 14708009 DOI: 10.1038/nrm1276] [Citation(s) in RCA: 577] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Polyploidy is a frequent phenomenon in the eukaryotic world, but the biological properties of polyploid cells are not well understood. During evolution, polyploidy is thought to be an important mechanism that contributes to speciation. Polyploid, usually non-dividing, cells are formed during development in otherwise diploid organisms. A growing amount of evidence indicates that polyploid cells also arise during a variety of pathological conditions. Genetic instability in these cells might provide a route to aneuploidy and thereby contribute to the development of cancer.
Collapse
Affiliation(s)
- Zuzana Storchova
- Department of Pediatric Oncology of The Dana-Farber Cancer Institute, Children's Hospital and Harvard Medical School, Room M621A, 44 Binney Street Boston, Massachusetts 02115, USA
| | | |
Collapse
|
173
|
Kladnik A, Vilhar B, Chourey PS, Dermastia M. Sucrose synthase isozyme SUS1 in the maize root cap is preferentially localized in the endopolyploid outer cells. ACTA ACUST UNITED AC 2004. [DOI: 10.1139/b03-143] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The structure of the maize (Zea mays L.) root cap was studied to quantitatively evaluate the relationship among the size of the cells, their endopolyploidy level, and the abundance of the sucrose synthase isozyme SUS1. Median longitudinal root cap sections were analysed using immunolocalization, quantitative DNA staining, and image cytometry. Both the immunolocalization signal for the SUS1 protein and the endopolyploidy level increased from calyptrogen towards the root cap periphery and were thus the highest in the outer cells. These cells had a nuclear DNA content of mostly 8C or higher and the largest volumes of all root cap cells. The high amount of SUS1 protein in the outer, endopolyploid cells suggests an association between endoreduplication and the abundance of this enzyme. The outer cells are involved in mucilage production; hence, there is a possibility that sucrose synthase provides monosaccharide precursors for mucilage synthesis.Key words: nuclear DNA amount, endoreduplication, immunolocalization, image cytometry, Zea mays L.
Collapse
|
174
|
Dan H, Imaseki H, Wasteneys GO, Kazama H. Ethylene stimulates endoreduplication but inhibits cytokinesis in cucumber hypocotyl epidermis. PLANT PHYSIOLOGY 2003; 133:1726-31. [PMID: 14645725 PMCID: PMC300727 DOI: 10.1104/pp.103.025783] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2003] [Revised: 06/26/2003] [Accepted: 08/18/2003] [Indexed: 05/19/2023]
Abstract
The effects of ethylene on cell division are generally considered inhibitory. In this study, we demonstrate that transient ethylene exposure, while suppressing cytokinesis, stimulates DNA synthesis. We monitored DNA synthesis and cytokinesis in the epidermis of cucumber (Cucumis sativus) hypocotyls, an organ whose post-germination development involves strictly limited cell division. During exposure to ethylene, DNA synthesis, assessed by the incorporation of the thymidine homolog 5-bromo-2'-deoxyuridine, was detected in 20% of the epidermal cells, whereas DNA synthesis was nearly undetectable in normal air. Cytofluorometric analysis of nuclei in affected cells showed an up to 8-fold increase in DNA content. During this time, new cell plate formation was not detected. However, shortly after ethylene was removed, DNA content was rapidly restored to 2C (diploid) levels in all cells, and new cell plate formation dramatically increased. These results demonstrate that ethylene promotes DNA synthesis and its endoreduplication but inhibits cytokinesis, thereby maintaining some cells in G2 phase.
Collapse
Affiliation(s)
- Haruka Dan
- Department of Biology, International Christian University, Mitaka, Tokyo 181-8585 Japan
| | | | | | | |
Collapse
|
175
|
Sugimoto-Shirasu K, Roberts K. "Big it up": endoreduplication and cell-size control in plants. CURRENT OPINION IN PLANT BIOLOGY 2003; 6:544-53. [PMID: 14611952 DOI: 10.1016/j.pbi.2003.09.009] [Citation(s) in RCA: 342] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Cells undergoing endoreduplication replicate chromosomal DNA without intervening mitoses. The resulting larger, higher-ploidy nucleus is often associated with an increase in cell size, but the molecular basis for this correlation remains poorly understood. Recent advances in characterising various mutants and transgenic plants are beginning to unravel how this unique type of cell cycling is regulated and how it contributes to cell-size control. Both cell growth (i.e. increase in cytoplasmic macromolecular mass) and cell expansion (i.e. increase in cell volume through vacuolation) contribute independently to increases in cell size in plants. A total organ-size checkpoint may also help to coordinate cell size and cell number within an organ, and can contribute to final cell-size determination in plants.
Collapse
Affiliation(s)
- Keiko Sugimoto-Shirasu
- Department of Cell and Developmental Biology, John Innes Centre, Colney, Norwich, NR4 7UH, UK.
| | | |
Collapse
|
176
|
Apse MP, Sottosanto JB, Blumwald E. Vacuolar cation/H+ exchange, ion homeostasis, and leaf development are altered in a T-DNA insertional mutant of AtNHX1, the Arabidopsis vacuolar Na+/H+ antiporter. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 36:229-39. [PMID: 14535887 DOI: 10.1046/j.1365-313x.2003.01871.x] [Citation(s) in RCA: 212] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The function of vacuolar Na+/H+ antiporter(s) in plants has been studied primarily in the context of salinity tolerance. By facilitating the accumulation of Na+ away from the cytosol, plant cells can avert ion toxicity and also utilize vacuolar Na+ as osmoticum to maintain turgor. As many genes encoding these antiporters have been cloned from salt-sensitive plants, it is likely that they function in some capacity other than salinity tolerance. The wide expression pattern of Arabidopsis thaliana sodium proton exchanger 1 (AtNHX1) in this study supports this hypothesis. Here, we report the isolation of a T-DNA insertional mutant of AtNHX1, a vacuolar Na+/H+ antiporter in Arabidopsis. Vacuoles isolated from leaves of the nhx1 plants had a much lower Na+/H+ and K+/H+ exchange activity. nhx1 plants also showed an altered leaf development, with reduction in the frequency of large epidermal cells and a reduction in overall leaf area compared to wild-type plants. The overexpression of AtNHX1 in the nhx1 background complemented these phenotypes. In the presence of NaCl, nhx1 seedling establishment was impaired. These results place AtNHX1 as the dominant K+ and Na+/H+ antiporter in leaf vacuoles in Arabidopsis and also suggest that its contribution to ion homeostasis is important for not only salinity tolerance but development as well.
Collapse
Affiliation(s)
- Maris P Apse
- Department of Pomology, University of California, One Shields Ave, Davis, CA 95616, USA
| | | | | |
Collapse
|
177
|
Abstract
• Occurrence of endopolyploidy in somatic tissues of the hybrid orchid Vanda Miss Joaquim (Vanda hookeriana × Vanda teres) was investigated with respect to tissue type and developmental stage. Effects of naphthaleneacetic acid (NAA) and gibberellic acid (GA3 ) on endopolyploidy during embryo development were also studied. • For the study of endopolyploidy, flow cytometric analysis was employed to determine nuclear DNA content of cells of somatic tissues. • Multiploid cells were observed in leaves, roots and column, but not in shoot apex, stem, perianth and pedicel. Furthermore, differential distribution of multiploid cells was found among different parts of leaves and roots. The degree of endopolyploidy in embryos increased with development. NAA was shown to induce endoreduplication in germinating embryos to a much larger extent than GA3 . • The pattern of endopolyploidy was characteristic of tissue type and developmental stage. The implications of endopolyploidy during differentiation and development, as well as the relevance of endopolyploidy to somaclonal variation, are discussed.
Collapse
Affiliation(s)
- Wan Li Lim
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Chiang Shiong Loh
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543
| |
Collapse
|
178
|
Abstract
Topoisomerase VI is a unique type II topoisomerase originally identified in archaea. Although lacking in most eukaryotic phyla, topoisomerase VI homologs have been recently identified and characterized in the plant Arabidopsis thaliana. Three new studies of Arabidopsis topoisomerase VI show that this enzyme is important to several processes involving DNA replication and gene expression.
Collapse
Affiliation(s)
- Kevin D Corbett
- Department of Molecular and Cellular Biology, 327 Hildebrand Hall #3206, University of California, Berkeley, Berkeley, CA 94720, USA
| | | |
Collapse
|
179
|
Abstract
The nucleus is the cellular organelle in which the bulk of the genomic information is stored. From studies using fluorescence microscopy with optical sections of fixed cells, a picture of an organized nuclear structure has emerged. Recently, the application of the green fluorescent protein (GFP) as a fluorescent dye allows the visualization of nuclear dynamics in live cells. Using four-dimensional fluorescence microscopy, the nuclear structures within an interphase nucleus are perceived to have dynamic domains. Structural analyses of a living plant nucleus contribute to our understanding of the genome information process in a particular cell in multicelluar systems.
Collapse
Affiliation(s)
- Naohiro Kato
- Biotechnology Center for Agriculture and the Environment, Rutgers, The State University of New Jersey, 59 Dudley Road, Foran Hall, New Brunswick, New Jersey 08901-8520, USA
| |
Collapse
|
180
|
Jasmer DP, Goverse A, Smant G. Parasitic nematode interactions with mammals and plants. ANNUAL REVIEW OF PHYTOPATHOLOGY 2003; 41:245-70. [PMID: 14527330 DOI: 10.1146/annurev.phyto.41.052102.104023] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Parasitic nematodes that infect humans, animals, and plants cause serious diseases that are deleterious to human health and agricultural productivity. Chemical and biological control methods have reduced the impact of these parasites. However, surviving environmental stages lead to persistent reinfection of host species. In addition, development of resistance to nematicides and anthelmintics by these parasites and reduced availability of some nematicides, for environmental protection, pose significant obstacles for current and future prospects of effective parasite control. Due to marked differences in host species, research on animal and plant parasitic nematodes often proceeds independently. Despite the differences between animals and plants, basic cellular properties are shared among these host organisms. Some common properties may be important for mechanisms [homologous or convergent (homoplastic)] by which nematodes successfully infect these diverse hosts or by which animal and plant hosts resist infections by these pathogens. Here we compare host/parasite interactions between plant parasitic nematodes (PPN) and animal parasitic nematodes, with an emphasis on mammalian hosts (MPN). Similarities and differences are considered in the context of progress on molecular dissection of these interactions. A comprehensive coverage is not possible in the space allotted. Instead, an illustrative approach is used to establish examples that, it is hoped, exemplify the value of the comparative approach.
Collapse
Affiliation(s)
- Douglas P Jasmer
- Department of Veterinary Microbiology, Washington State University, Pullman, Washington, 99164-7040, USA.
| | | | | |
Collapse
|
181
|
Sugimoto-Shirasu K, Stacey NJ, Corsar J, Roberts K, McCann MC. DNA topoisomerase VI is essential for endoreduplication in Arabidopsis. Curr Biol 2002; 12:1782-6. [PMID: 12401175 DOI: 10.1016/s0960-9822(02)01198-3] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Endoreduplication is a common process in eukaryotes that involves DNA amplification without corresponding cell divisions. Cell size in various organisms has been linked to endoreduplication, but the molecular mechanisms are poorly understood. We have used a genetic strategy to identify molecules involved in endocycles in Arabidopsis. We isolated two extreme dwarf mutants, hypocotyl6 (hyp6) and root hairless2 (rhl2) [3], and cells of these mutants successfully complete only the first two rounds of endoreduplication and stall at 8C. In both mutants, large cell types, such as trichomes and some epidermal cells, that normally endoreduplicate their DNA are much reduced in size. We show that HYP6 encodes AtTOP6B, a plant homolog of the archaeal DNA topoisomerase VI subunit B, and that RHL2 encodes AtSPO11-3, one of the three Arabidopsis subunit A homologs. We propose that this topoisomerase VI complex is essential for the decatenation of replicated chromosomes during endocycles and that successive rounds of endoreduplication are required for the full growth of specific cell types.
Collapse
Affiliation(s)
- Keiko Sugimoto-Shirasu
- Department of Cell and Developmental Biology, John Innes Centre, Colney, Norwich, United Kingdom
| | | | | | | | | |
Collapse
|
182
|
Beemster GTS, De Vusser K, De Tavernier E, De Bock K, Inzé D. Variation in growth rate between Arabidopsis ecotypes is correlated with cell division and A-type cyclin-dependent kinase activity. PLANT PHYSIOLOGY 2002; 129:854-64. [PMID: 12068124 PMCID: PMC161706 DOI: 10.1104/pp.002923] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2002] [Revised: 03/11/2002] [Accepted: 03/22/2002] [Indexed: 05/17/2023]
Abstract
We used a kinematic analysis to investigate the growth processes responsible for variation in primary root growth between 18 ecotypes of Arabidopsis. Root elongation rate differed 4-fold between the slowest (Landsberg erecta, 71 microm h(-1)) and fastest growing line (Wassilewskija [Ws]; 338 microm h(-1)). This difference was contributed almost equally by variations in mature cortical cell length (84 microm [Landsberg erecta] to 237 microm [Ws]) and rate of cell production (0.63 cell h(-1) [NW108] to 1.83 cell h(-1) [Ws]). Cell production, in turn, was determined by variation in cell cycle duration (19 h [Tsu] to 48 h [NW108]) and, to a lesser extent, by differences in the number of dividing cells (32 [Weiningen] to 61 [Ws]). We found no correlation between mature cell size and endoreduplication, refuting the hypothesis that the two are linked. However, there was a strong correlation between cell production rates and the activity of the cyclin-dependent kinase (CDKA). The level of the protein could explain 32% of the variation in CDKA. Therefore, it is likely that regulators of CDKA, such as cyclins and inhibitors, are also involved. These data provide a functional link between cell cycle regulation and whole-plant growth rate as affected by genetic differences.
Collapse
Affiliation(s)
- Gerrit T S Beemster
- Department of Plant Genetics, University of Gent/Flanders Institute of Biotechnology, B-9000 Gent, Belgium
| | | | | | | | | |
Collapse
|
183
|
Vilhar B, Kladnik A, Blejec A, Chourey PS, Dermastia M. Cytometrical evidence that the loss of seed weight in the miniature1 seed mutant of maize is associated with reduced mitotic activity in the developing endosperm. PLANT PHYSIOLOGY 2002; 129:23-30. [PMID: 12011334 PMCID: PMC1540223 DOI: 10.1104/pp.001826] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Affiliation(s)
- Barbara Vilhar
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Vecna pot 111, SI-1001 Ljubljana, Slovenia
| | | | | | | | | |
Collapse
|
184
|
Kudo N, Kimura Y. Nuclear DNA endoreduplication during petal development in cabbage: relationship between ploidy levels and cell size. JOURNAL OF EXPERIMENTAL BOTANY 2002; 53:1017-1023. [PMID: 11971913 DOI: 10.1093/jexbot/53.371.1017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The development of cabbage petals comprises two distinct phases: a cell division phase and a consecutive phase of cell expansion until the onset of opening. In this study, cytological changes characterizing the two phases of petal development were analysed. First, the mitotic activity and the surface area of epidermal cells during petal development were investigated. The DNA content of isolated nuclei from the different stages of petal tissues was determined by flow cytometric analysis. The results show that cell differentiation, leading to expanded cells, is characterized by endoreduplication. In the proximal part of the petal, after cell division arrest, differentiation frequently involves endoreduplication and cell enlargement. By contrast, normal diploid nuclei remained in the distal part of the lamina in the mature petal. It is suggested that the developmental programmes of the cabbage petal may be a trigger for the initiation of endoreduplication. Correlation between ploidy levels and cell size is also discussed.
Collapse
Affiliation(s)
- Nobuhiro Kudo
- Division of Plant Biotechnology, Gunma Horticultural Experiment Station, 493 Nishi-Obokata, Sawa-Azuma, Gunma 379-2224, Japan.
| | | |
Collapse
|
185
|
Mizukami Y. A matter of size: developmental control of organ size in plants. CURRENT OPINION IN PLANT BIOLOGY 2001; 4:533-9. [PMID: 11641070 DOI: 10.1016/s1369-5266(00)00212-0] [Citation(s) in RCA: 161] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The intrinsic size of plant organs is determined by developmental signals, yet the molecular and genetic mechanisms that control organ size are largely unknown. Ongoing functional analysis of Arabidopsis genes is defining important regulators involved in these mechanisms. Key features of this control are the coordinated activation of growth and cell division by growth regulators and the maintenance of meristematic competence by the ANT gene, which acts as an organ-size checkpoint. Alterations of genome size by polyploidization and endoreduplication can reset this checkpoint by ploidy-dependent, epigenetically regulated differential gene expression. In addition, the regulation of polarized growth and phytohormone signaling also affect final organ size. These findings reveal unique aspects of plant organ-size control that are distinct from animal organ-size control.
Collapse
Affiliation(s)
- Y Mizukami
- Department of Plant and Microbial Biology, University of California, 231 Koshland Hall, Berkeley, California 94720, USA.
| |
Collapse
|
186
|
Abstract
Plant cells adopt a diversity of different shapes that are adapted to their specific functions. Central to the development of specialised form is the modification of cell-wall composition and organisation. A number of recent papers emphasise the importance of the cell wall to cell shaping, in the definition of both localised regions that are expandable and regions that are more resistant to mechanical forces. The organisation and activity of the cytoskeleton, and the activity of signalling pathways, are also essential in defining regions of the cell wall that will grow and those that will not. Although turgor has long been assumed to be a rather passive contributor to cell shaping, recent reports show that, in some cells, differential changes in turgor may have a role in establishing specialised cell form.
Collapse
Affiliation(s)
- C Martin
- Department of Cell and Developmental Biology, John Innes Centre, Colney, NR4 7UH, Norwich, UK
| | | | | |
Collapse
|
187
|
Montagne J. Genetic and molecular mechanisms of cell size control. MOLECULAR CELL BIOLOGY RESEARCH COMMUNICATIONS : MCBRC 2000; 4:195-202. [PMID: 11409911 DOI: 10.1006/mcbr.2001.0284] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Since the discovery of the cell as the minimal indivisible living entity, scientists have tried to understand how all the various physiological aspects were assumed within this single functional unit. One fascinating question concerns the role of cell size and cell number in determining the overall size of an organism. During the past century, increasing knowledge in molecular genetics has allowed the characterization of a number of molecular events that influence the size of a cell. However, in spite of recent progress, precise molecular mechanisms governing cell size remain unclear. Although the existence of a master regulator is still possible, cell size may be primarily controlled by an interactive network linking gene expression with translational capacity and cell proliferation.
Collapse
Affiliation(s)
- J Montagne
- Friedrich Miescher-Institut, Maulbeerstrasse 66, Basel, CH-4058, Switzerland.
| |
Collapse
|