Interphase nuclear structure and heterochromatin in Cicer species
25 Mar 1989-Cytologia (Japan Mendel Society, International Society of Cytology)-Vol. 54, Iss: 1, pp 27-32
TL;DR: Interphase nuclear organization was studied in six species of Cicer and all the species showed chromocentric nuclear organization in both meristematic and differentiated cells instead of reticulate organization, which can be considered as primitive of the six Cicer species.
Abstract: Interphase nuclear organization was studied in six species of Cicer and all the species showed chromocentric nuclear organization in both meristematic and differentiated cells instead of reticulate organization. The number of chromocentres and treatment duration with acid or alkali were found to be species specific character. Percentage heterochromatin values determined by two different techniques were somewhat high in meristematic cells than those in differentiated cells. On the basis of heterochromatin values both in meristematic and differentiated cells C. reticulaturn can be considered as primitive of the six Cicer species. Nuclear organization was found to be governed by small size of chromosomes and low DNA content, but the relationship between heterochromatin values and DNA content was not clear.
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TL;DR: It is demonstrated that cycles of endoreduplication or other methods of DNA amplification are insufficient to drive giant cell expansion and that syncytium expansion was inhibited by a mitotic block.
Abstract: Root knot and cyst nematodes induce large multinucleated cells, designated giant cells and syncytia, respectively, in plant roots. We have used molecular markers to study cell cycle progression in these specialized feeding cells. In situ hybridization with two cyclin-dependent kinases and two cyclins showed that these genes were induced very early in galls and syncytia and that the feeding cells progressed through the G2 phase. By using cell cycle blockers, DNA synthesis and progression through the G2 phase, or mitosis, were shown to be essential for gall and syncytium establishment. When mitosis was blocked, further gall development was arrested. This result demonstrates that cycles of endoreduplication or other methods of DNA amplification are insufficient to drive giant cell expansion. On the other hand, syncytium development was much less affected by a mitotic block; however, syncytium expansion was inhibited.
210 citations
Cites background from "Interphase nuclear structure and he..."
...Chromocenters were also larger than those in nuclei of neighboring cells, probably because of overlapping, fusion, or polyteny (Kabir and Singh, 1989)....
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TL;DR: The current views of plant cell fate manipulation by these sedentary nematodes are integrated and an inventory of possible links between cell cycle activation and local, nematode-induced changes in auxin levels are made.
Abstract: Sedentary nematodes are important pests of crop plants. They are biotrophic parasites that can induce the (re)differentiation of either differentiated or undifferentiated plant cells into specialized feeding cells. This (re)differentiation includes the reactivation of the cell cycle in specific plant cells finally resulting in a transfer cell-like feeding site. For growth and development the nematodes fully depend on these cells. The mechanisms underlying the ability of these nematodes to manipulate a plant for its own benefit are unknown. Nematode secretions are thought to play a key role both in plant penetration and feeding cell induction. Research on plant-nematode interactions is hampered by the minute size of cyst and root knot nematodes, their obligatory biotrophic nature and their relatively long life cycle. Recently, insights into cell cycle control in Arabidopsis thaliana in combination with reporter gene technologies showed the differential activation of cell cycle gene promoters upon infection with cyst or root knot nematodes. In this review, we integrate the current views of plant cell fate manipulation by these sedentary nematodes and made an inventory of possible links between cell cycle activation and local, nematode-induced changes in auxin levels.
92 citations
Cites background from "Interphase nuclear structure and he..."
...However, chromocentres sometimes fuse resulting in fewer and larger chromocentres (Kabir and Singh, 1989)....
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01 Jan 2011
TL;DR: Microscopic expression analysis of genes that encode key regulators of the cell cycle and the use of cell cycle inhibitors demonstrate that endoreduplication cycles may play a role in both giant cell and syncytium formation, while mitosis is essential for giant cell development and synCytium expansion.
Abstract: Cell cycle activation is a key component of host plant manipulation by sedentary nematodes. It is generally believed that root-knot nematodes induce giant cells by repeated cycles of acytokinetic mitosis accompanied by endocycles while cyst nematodes induce extra rounds of DNA synthesis. Microscopic expression analysis of genes that encode key regulators of the cell cycle and the use of cell cycle inhibitors demonstrate that endoreduplication cycles may play a role in both giant cell and syncytium formation, while mitosis is essential for giant cell development and syncytium expansion (via fusion of neighbouring cells). When mitosis is blocked, gall development is completely inhibited, indicating that cycles of endoreduplication or other means of DNA amplification are insufficient to drive giant cell expansion. DNA synthesis is required for both gall and syncytium development.
24 citations
TL;DR: Chromocentre numbers in two species of Corchorus and their hybrid were more or less same, which were, however, found to reduce than the expected number of 14.
Abstract: Interphase nuclear structure and heterochromatin were studied in Corchorus olitorius, Corchorus capsularis and their F1 hybrid by HCl-Giemsa and BSG-technique. Nuclear structure was chromocentric in both the parents and the hybrid. Chromocentre numbers in two species of Corchorus and their hybrid were more or less same, which were, however, found to reduce than the expected number of 14. Heterochromatin values yielded by HCl-Giemsa technique were slightly higher than those yielded by BSG treatment. The percentage of heterochromatin in F1 was found to be closer to the male parent. DNA contents were also estimated in both the parents and their hybrid but the relationship between DNA contents and heterochromatin value was not clear.
18 citations
Cites background or methods from "Interphase nuclear structure and he..."
...This might be due fusion or overlapping of chro mocentres indicating the somatic association of chromosomes (Kabir and Singh 1989)....
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...In Phaseolus (Joshi and Ranjekar 1983) and in Cicer (Kabir and Singh 1989) the methods used...
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TL;DR: Indications of somatic association were evident in interphase, prophase and metaphase stages of root tip mitosis and possible origin of vanilla as a hybrid is suggested.
Abstract: SUMMARYAbnormal mitotic behaviour in Vanilla planifolia is analysed with special emphasis to association of somatic chromosomes. Indications of somatic association were evident in interphase, prophase and metaphase stages of root tip mitosis. Reasons for somatic association is discussed. Possible origin of vanilla as a hybrid is suggested. Role of somatic association in enriching variability is also discussed.
18 citations
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TL;DR: The present study arose from the observation that a more intense colour was sometimes produced if, instead of being heated at 1000 for 10 min., the reaction mixture was allowed to stand overnight at room temperature.
Abstract: Of the colour reactions available for the determination and identification of deoxyribonucleic acid (DNA), the reaction with diphenylamine in a mixture of acetic and sulphuric acids at 1000 (Dische, 1930) has been perhaps the most widely used. The present study arose from the observation that a more intense colour was sometimes produced if, instead of being heated at 1000 for 10 min., the reaction mixture was allowed to stand overnight at room temperature. As a result of this observation the procedure has been modified, principally by adding acetaldehyde to the reagents and by allowing the solution to stand for about 17 hr. at 30° instead of heating it at 1000. The modified method is 3-5 times as sensitive as Dische's original procedure, and several substances which interfere in the original method do not do so in the modified procedure. Some observations on the mechanism of the reaction have been made; in particular it was discovered that there is a liberation of inorganic orthophosphate from DNA during the early stages of the reaction. This finding has a bearing on the structure of DNA. The modified method has already been used in an investigation of nucleic acid metabolism during bacteriophage multiplication (Burton, 1955).
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