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Results for “Endoreduplication”

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At least 145 records · Page 8Linked to original sources
PubMed2003

Ethylene stimulates endoreduplication but inhibits cytokinesis in cucumber hypocotyl epidermis.

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.

Cell Division↗
PubMed2004

The immunophilin-interacting protein AtFIP37 from Arabidopsis is essential for plant development and is involved in trichome endoreduplication.

The FKBP12 (FK506-binding protein 12 kD) immunophilin interacts with several protein partners in mammals and is a physiological regulator of the cell cycle. In Arabidopsis, only one specific partner of AtFKBP12, namely AtFIP37 (FKBP12 interacting protein 37 kD), has been identified but its function in plant development is not known. We present here the functional analysis of AtFIP37 in Arabidopsis. Knockout mutants of AtFIP37 show an embryo-lethal phenotype that is caused by a strong delay in endosperm development and embryo arrest. AtFIP37 promoter::beta-glucuronidase reporter gene constructs show that the gene is expressed during embryogenesis and throughout plant development, in undifferentiating cells such as meristem or embryonic cells as well as highly differentiating cells such as trichomes. A translational fusion with the enhanced yellow fluorescent protein indicates that AtFIP37 is a nuclear protein localized in multiple subnuclear foci that show a speckled distribution pattern. Overexpression of AtFIP37 in transgenic lines induces the formation of large trichome cells with up to six branches. These large trichomes have a DNA content up to 256C, implying that these cells have undergone extra rounds of endoreduplication. Altogether, these data show that AtFIP37 is critical for life in Arabidopsis and implies a role for AtFIP37 in the regulation of the cell cycle as shown for FKBP12 and TOR (target of rapamycin) in mammals.

Amino Acid Sequence↗
PubMed1993

Role of Auxin in Maize Endosperm Development (Timing of Nuclear DNA Endoreduplication, Zein Expression, and Cytokinin).

The timing of developmental events and regulatory roles of auxin were examined in maize (Zea mays L.) endosperms. Zeatin, zeatin riboside, and indole-3-acetic acid (IAA) levels were determined by enzyme-linked immunosorbent (ELISA). Zeatin and zeatin riboside increased to maximal concentrations at an early stage (9 d after pollination [DAP]), corresponding to the stage when cell division rate was maximal. In contrast, IAA concentration was low at 9 DAP and abruptly increased from 9 to 11 DAP, thus creating a sharp decline in the cytokinin to auxin ratio. Coincident with the increase in IAA was an increase in DNA content per nucleus, attributed to postmitotic DNA replication via endoreduplication. Exogenous application of 2,4-dichlorophenoxyacetic acid (2,4-D) at 5 or 7 DAP hastened the time course of DNA accumulation per nucleus and increased the average nuclear diameter, whereas 2-(para-chlorophenoxy)isobutyric acid delayed such development. Exogenously applied 2,4-D hastened the accumulation of the zein polypeptides of apparent molecular masses of 12, 14, and 16 kD and the expression of mRNA hybridizing with a zein DNA probe. We conclude that an abrupt increase in auxin induces cellular differentiation events in endosperm, including endoredupliction and expression of particular zein storage proteins.

Journal Article↗
PubMed2005

Cell expansion and endoreduplication show a large genetic variability in pericarp and contribute strongly to tomato fruit growth.

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.

Cell Enlargement↗
PubMed1979

Inherited aplastic anaemia with increased endoreduplications: a new syndrome of Fanconi's anaemia variant?

Two sisters with aplastic anaemia without other congenital anomalies are described. Peripheral blood cytogenetic studies revealed an increase in endoreduplications in the absence of other unstable chromosome anomalies. Increased expression of T-antigen following SV40 virus infection in vitro was demonstrated in both sisters, as well as other normal family members. We feel that these patients represent a variant of Fanconi's anaemia. The importance of performing chromosome studies in idiopathic aplastic anaemia is emphasized.

Adolescent↗
PubMed1976

Evidence for chromosome endoreduplication in Eudorina californica, a colonial alga.

Several nuclear events seen during the cleavage period in Eudorina suggest that chromosome endoreduplication, proportional to the number of cells to be produced, may occur in the gonidia prior to cleavage. Presumably the DNA concentration is reduced to the haploid level during rapid, successive divisions of the cleavage period. To test this hypothesis, I determined DNA content of gonidia as they grew from 4 mum to 38 mum in diameter between cleavage periods. During growth from 4 mum to 8 mum in diameter, the DNA concentration remained at the haploid level of 0.17 pg/cell. As gonidia in 64 cell colonies continued to grow from 8 mum to 33 mum in diameter, their DNA concentrations increased 60-fold. Analysis of the Eudorina DNA by equilibrium centrifugation in CsCl showed only 2 bands with buoyant densities of 1.721 g/cm3 and 1.699 g/cm3, presumed to be nuclear and chloroplast, respectively, on the basis of labelling with 3H-thymidine and 3H-adenine. The 8:2 ratio of the two bands did not change with increase in cell size and no other bands were detected, suggesting that both nuclear and chloroplast DNAs were synthesised proportionately prior to the cleavage period.

Cell Division↗
PubMed2004

Histone mRNAs do not accumulate during S phase of either mitotic or endoreduplicative cycles in the chordate Oikopleura dioica.

Metazoan histones are generally classified as replication-dependent or replacement variants. Replication-dependent histone genes contain cell cycle-responsive promoter elements, their transcripts terminate in an unpolyadenylated conserved stem-loop, and their mRNAs accumulate sharply during S phase. Replacement variant genes lack cell cycle-responsive promoter elements, their polyadenylated transcripts lack the stem-loop, and they are expressed at low levels throughout the cell cycle. During early development of some organisms with rapid cleavage cycles, replication-dependent mRNAs are not fully S phase restricted until complete cell cycle regulation is achieved. The accumulation of polyadenylated transcripts during this period has been considered incompatible with metazoan development. We show here that histone metabolism in the urochordate Oikopleura dioica does not accord with some key tenets of the replication-dependent/replacement variant paradigm. During the premetamorphic mitotic phase of development, expressed variants shared characteristics of replication-dependent histones, including the 3' stem-loop, but, in contrast, were extensively polyadenylated. After metamorphosis, when cells in many tissues enter endocycles, there was a global downregulation of histone transcript levels, with most variant transcripts processed at the stem-loop. Contrary to the 30-fold S-phase upregulation of histone transcripts described in common metazoan model organisms, we observed essentially constant histone transcript levels throughout both mitotic and endoreduplicative cell cycles.

Amino Acid Sequence↗
PubMed1985

Studies on endoreduplication. V. A three-dimensional scheme for diplo- and quadruple chromosomes and a model for DNA replication.

The metaphase appearance of quadruple chromosomes in colchicine-treated CHO cells was compared between air-dried and gently squashed preparations. A marked difference in morphology between the two methods suggested that the planar alignment of quadruple chromosomes is an artifact of the spreading process and that quadruple chromosomes are organized within the nucleus in a three-dimensional configuration. By analyzing the alignment of the original and replicated strands, using BrdU incorporation, the three-dimensional orientation of the chromatids in quadruple chromosomes could be traced. This analysis led to a new model for DNA replication. According to this model, an opening of a DNA base pair which rotates about 90 degrees with respect to the deoxyribose phosphate backbone precedes DNA replication, resulting in the formation of the newly replicated strands perpendicular to the original plane of the base pair. This model, although derived from endoreduplication, may be applicable to a general scheme for DNA replication during normal chromosome duplication.

Animals↗
PubMedDate not supplied

[Effect of parental age on endoreduplication of giant chromosomes and some quantitative traits in Drosophila melanogaster descendants].

We studied the influence of parental age on the degree of polyteny of giant chromosomes and expressivity of mutation eyeless in Drosophila melanogaster descendants. The parental age equal to six days exerted an adverse effect on the function of endoreduplication of giant chromosomes in strain eyeless. The highest degree of polyteny was observed in descendants of four- and ten-day imago. The maximum reduction of eye facets was observed in descendants of four-day imago, while in the progeny of older parents, the mutation expressivity was sharply reduced. Relations between the changes in chromosome polyteny, expressivity of mutation eyeless, and earlier studied components of adaptation were statistically analyzed in descendants of aging parents of this Drosophila strain.

Aging↗