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At least 451 records · Page 25Linked to original sources

PubMed2002

[Disruption of organization of mitotic microtubules in root meristem cells of Allium cepa induced by chloral hydrate].

Data are presented on the effect of chlorahydrate on microtubule organization in the root meristem of Allium cepa. Our studies show that an incomplete preprophase band commonly appears during G2-prophase transition, yet the major effect is the lack of perinuclear microtubules, leading to inhibition of the prophase spindle formation and transition to C-mitosis. Upon chloralhydrate treatment of metaphase cells, we found cells with chromosomes regularly aligned within the metaphase plate and differently disorganized mitotic spindles. Concurrently, C-metaphase cells with remnants of kinetochore fibers were present. In addition, normal bipolar and abnormal irregular types of chromosome segregation were detected, this representing multipolar and diffuse anaphases. The major difference between them is the presence of polar microtubules during multipolar anaphase, and their lacking during diffuse anaphase. Alternatively, microtubule clusters between segregated groups of chromosomes are typical for cells with diffuse anaphase. During bipolar anaphase, excessive aster-like microtubules emanate from the spindle poles, and in telophase accessory phragmoplasts are observed at the cell periphery. The formation of incomplete phragmoplasts was observed after normal bipolar and abnormal chromosome segregation. We conclude that chloralhydrate may affect the nuclear surface capability to initiate the growth of perinuclear microtubules, thus blocking the prophase spindle formation. It also disturbs the spatial interaction between microtubules, which is crucial for the formation and functioning of various microtubular systems (preprophase band, spindle and phragmoplast).

Allium↗

PubMedDate not supplied

[Peculiarities of the influence of chemical and physical factors on cytogenetic indices of root meristem in Pisum sativum L].

The results of comparative analysis of cytogenetic effects of various chemical and physical factors on meristemic cells of field pea (Pisum sativum L.) are presented. Cytogenetic effects of aluminum, cadmium and selenium compounds as well as X-ray irradiation were studied. Cytogenetic indices were investigated for different doses of the above factors and peculiarities of their influence on the ratio of mitotic phases were analyzed. The increasing in the proportion of cells at the specific mitotic stage was revealed. There were anaphase stage for aluminum chloride, prophase stage for cadmium chloride, meta- and anaphase stages for sodium selenate, and telophase stage for X-rays. Investigated chemical elements may be ranged according to their ability to induce the aberrant anaphase frequency in the row: Se (from 3.75 x 10(-6) M) > A1 (from 3.86 x 10(-5) M) > Cd (from 8.44 x 10(-5) M). Maximal experimental dose of X-ray irradiation (9.03 x 10(-3) C/kg) induces the frequency of chromosome aberration similar to those induced by maximal experimental doses of aluminum and selenium (3.86 x 10(-4) M and 8.34 x 10(-6) M).

Aluminum Chloride↗

PubMedDate not supplied

[Effect of separate radioactive and chemical pollutants on the yield of cytogenetic disruptions in the intercalary meristem in spring barley].

Dependencies of the yield of cytogenetic disturbances within intercalary meristem cells of spring barley on the soil level of 137Cs (1.48-14.8 MBq/m2), Cd, Pb (2-50 and 30-300 mg per kilogram of the soil) and 2.4-D herbicide (1 or 2 kg/ha) had a non-linear character in the studied range. At low concentrations the yield of cytogenetic disturbances grew faster than at higher ones. Concentrations of lead in soil (at the level of maximum concentration limit) and doses of 2.4-D recommended for agricultural use resulted in the increase in the rate of aberrant cells. The observed rate of cytogenetic disturbances was comparable with the effect of the maximum studied level or the radioactive soil pollution. The heaviest damage to aberrant cells was found in the presence of 137Cs.

2,4-Dichlorophenoxyacetic Acid↗

PubMedDate not supplied

[Effect of combined radioactive and chemical (heavy metals, herbicides) pollution on the yield of cytogenetic disruptions in the intercalary meristem of spring barley].

The yield of aberrant cells and their loading with lesions of intercalary meristem of spring barley in conditions of the combined action of 137Cs, heavy metals and 2.4-D herbicide was studied. At simultaneous insertion of 137Cs and Cd into the soil, the type of non-linearity of the yield of aberrant cells was determined by radioactive pollution: in a range of low concentrations the synergistic effects took place, in a range of higher ones the antagonistic effects did. In the presence of cadmium, the severity of radiation induced damage to aberrant cells was significantly less. The interaction in 137Cs-Pb pair had an antagonistic character. The yield of aberrant cells was determined mainly by lead, whereas the radioactive pollution played the main role in loading of the aberrant cells with lesions. At the combined pollution with 137Cs and other contaminants, the antagonistic effects were more pronounced with Pb than with Cd, and further increased with the herbicide, both in the test on frequency of aberrant cells and the test on the loading of aberrant cells with lesions. In case of combination of the chemical agents the non-linear effects in test on loading of aberrant cells with lesions were mainly synergistic, whereas in the test on frequency of aberrant cells they were antagonistic. Only Pb-Cd pair and only in the test on loading of aberrant cells with lesions no significant non-linear effects were found. The results show high rate of the induction of synergistic and antagonistic effects in conditions of the combined action of low concentrations of the investigated agents on plants. These effects substantially determined the yield of cytogenetic disturbances in the studied range.

2,4-Dichlorophenoxyacetic Acid↗

PubMedDate not supplied

Polyamines and fatty acids in sucrose precultured banana meristems and correlation with survival rate after cryopreservation.

Polyamines and fatty acids were studied in proliferating meristem cultures of 3 banana cultivars with high (Cachaco), medium (Williams Bronze free) and low (Mbwazirume) survival rates after cryopreservation. A 2-week preculture on medium containing 0.4 M sucrose which is essential to obtain survival after cryopreservation resulted in increased polyamine levels, especially putrescine. This increase in putrescine content was positively correlated with the survival rate after simple freezing or after vitrification. The total fatty acid content also increased after a 0.4 M sucrose pretreatment. However, only the ratio of unsaturated/saturated fatty acids correlated positively with the survival rate after cryopreservation. This is the first report showing a correlation of both putrescine increase and level of unsaturation of membrane lipids after sucrose treatment with survival rate after cryopreservation.

Cell Survival↗

PubMed2003

A protocol for shoot multiplication from foliar meristem of Vanda spathulata (L.) Spreng.

Leaf explants collected from flowering plants of Vanda spathulata were cultured in Mitra medium with combinations of 6-benzyladenine (BA; 13.2-88.8 microM) and indole-3-acetic acid (IAA; 0.0 -85.6 microM). Combination of BA (66.6 microM) and IAA (28.5 microM) induced maximum shoots (17.33) from foliar meristems (leaf base). BA individually did not induce caulogenesis in leaf explants. For optimized multiplication, BA:IAA (2:1 microM) was essential at 22.2- 88.8 microM of BA. Re-cultured leaf explants produced lesser number of shoots compared to original explants and were nearly equal at combinations of 22.2-44.4 microM of BA and 5.7-28.5 microM of IAA. Rooting of shoots (> 95%) occurred in medium containing banana pulp (75 gl(-1)) and IAA (5.7 microM) within 3-9 weeks. Plantlets with 2-5 roots of 2-5 cm length established easily in community pots at 80-90% rates without hardening.

Adenine↗

PubMedDate not supplied

[Expression of delta1- and delta3-cyclin genes in pea (pisum sativum L.) root meristem during clinorotation].

Using in situ hybridization the delta1- and delta3-cyclin gene expression has been shown in pea (Pisum sativum L.) root meristem cells under slow horizontal clinorotation and in the stationary conditions. The clinorotation effect on expression of these genes during pea root germination was detected. The delay of degradation of cyclin subunits is the cause of G1-phase prolongation under clinorotation leading to delay of pea seed germination. This may explain the increase of cell cycle duration.

Cyclins↗

PubMed1998

Cell cycle control protein p34cdc2 homologue and its phase specific accumulation in synchronized onion (Allium cepa L.) root meristem cells.

A key regulator of the cell cycle is a highly conserved protein kinase whose catalytic subunit, p34cdc2, is encoded by cdc2 gene. Immunoblotting with a polyclonal antibody raised against PSTAIRE sequence (found in the N-terminal region of all cdc2 and cdc2 related proteins throughout the phylogenetic scale including higher plants), was used to study the presence of p34cdc2 in onion scale leaves and root tip cells. p34cdc2 homologues are beyond the detection level in scale leaves. PSTAIRE antibody was used to estimate p34cdc2 kinase protein levels during cell cycle in highly synchronous population of Allium cepa L. root meristem cells. p34cdc2 kinase protein showed gradual increase in their levels from S phase to G2 phase boundary. Immunoprecipitation followed by in vitro histone H1 kinase assays also depicted that its kinase activity increased parallel to the increase in p34cdc2 level.

Amino Acid Sequence↗

PubMed1983

Chromosomal aberrations and delays in cell progression induced by X-rays in Tradescantia clone 02 meristems.

In root meristems of Tradescantia clone 02 (developed by Sparrow and his colleagues for mutation studies), X-rays interfere with the progression of cells through the cell cycle and induce chromosomal aberrations in a dose-dependent manner consistent with linear-quadratic kinetics. Sequential mitotic cell accumulations after irradiation indicate that sensitivity to aberration induction is probably greatest in cells from late S to early G2, with chromatid interchanges the most frequent aberration type and all aberrations consistent with initiation from the interaction between two lesions. The ratio of the coefficients in the linear (alpha) and the quadratic (beta) terms (alpha/beta) is equal to the dose average of specific energy produced by individual particles in the site where interaction takes place. The ratio alpha/beta for chromosomal aberrations is similar to that previously found for X-ray-induced mutation in Tradescantia stamen hairs, supporting the proposal that radiation-induced mutational events are due to chromosomal aberrations with interaction distances of about 1 micron. Abrahamson and co-workers have noted that both alpha/beta ratios appear to be related to nuclear target size and are similar for chromosomal and mutational endpoints in the same organism. These findings support this concept; however, it is apparent that any situation which diminishes yield at high doses (eg, mitotic delay) will primarily affect the beta component, resulting in low assessments of interaction site diameters.

Cell Cycle↗

PubMed1994

An S18 ribosomal protein gene copy at the Arabidopsis PFL locus affects plant development by its specific expression in meristems.

In Arabidopsis, mutation at PFL causes pointed first leaves, reduced fresh weight and growth retardation. We have cloned the wild-type PFL gene by T-DNA tagging, and demonstrate that it complements the mutant phenotype. PFL codes for ribosomal protein S18, based on the high homology with rat S18 and on purification of S18-equivalent peptides from plant ribosomes. pfl represents the first mutation in eukaryotic S18 proteins or their S13 prokaryotic counterparts, involved in translation initiation. Arabidopsis contains three S18 gene copies dispersed in the genetic map; they are all transcribed and code for completely identical proteins. No transcript is detected from the mutated gene, S18A. The activity of the S18A promoter is restricted to meristems, with a markedly high expression at the embryonic heart stage, and to wounding sites. This means that plants activate an extra copy of this ribosomal protein gene in tissues with cell division activity. We postulate that in meristematic tissues plants use transcriptional control to synthesize extra ribosomes to increase translational efficiency. In analogy with this, an additional, developmentally regulated gene copy might be expected for all ribosomal proteins.

Amino Acid Sequence↗

PubMed2026

Zea mays Drought-Overly Sensitive1/TUBA4 Is Wilty3, and Transcriptome Co-Expression Analysis of Shoot Meristem Mutant Tissues Reveals Wilty2/TUB6:Wi3 Interactions Associated With Stem Vascular Bundle Development.

Plant vasculature is essential for the transport of water, nutrients, and signaling molecules across organs, while also providing critical mechanical support for growth and development. Disruptions in vascular bundle formation can therefore lead to severe physiological and developmental defects. In maize, ethyl methanesulfonate (EMS)-induced dominant nonallelic Wilty mutants exhibit a pronounced wilting phenotype even under well-watered conditions, indicating underlying defects in vascular function. In this study, we characterized the Wi3 mutant, identified as ZmDrought-Overly-Sensitive1/DOS1, and compared it with the previously described Wi2 mutant to uncover shared mechanisms underlying their phenotypes. We provide evidence, by bulk segregant resequencing linkage disequilibrium of SNPs adjacent to the causal Wilty SNPs in respective ß- and α-tubulin genes, for the personal communication from Gerry Neuffer that Wi2/ß-tub6 provenance is from ACR-related stock, whereas Wi3/α-tub4 allele is from Mo17, not B73 as claimed by the authors who cloned Dos1. Histochemical staining and Fourier-transform infrared (FTIR) spectroscopy of vascular bundles in Wi3 indicated apparent alterations in cellulose and lignin content consistent with those observed in Wi2. Transcriptome analysis of shoot meristems further indicated that similar sets of genes and pathways are differentially expressed in both mutants, suggesting convergence on common biological pathways. Using bulk-segregant whole-genome resequencing, we identified alpha-tubulin4 (TUA4) as the causal gene in Wi3 (ZmDOS1), harboring a C-to-T substitution within the N-terminal GTPase-binding domain. This mutation results in a glutamic acid196-to-lysine substitution. Given that α- and β-tubulin subunits heterodimerize, and in many plants and animal mutant alleles are dominant-negative gains-of-function, we infer Wi2, Wi3, and likely Wi4, based on very similar FTIR biophysical difference spectra, may act as effectors of vascular bundle cell wall deposition, potentially involving vesicle trafficking as recently shown for asymmetric cell divisions in maize stomatal development. Together, these findings highlight the functional interdependence of tubulin subunits and provide a plausible mechanistic framework for the striking biophysical, transcriptomic, and phenotypic similarities observed between Wi2, Wi3/ZmDOS1, and Wi4 mutants.

bulk segregant analysis↗

PubMed1993

Localization of MPM-2 recognized phosphoproteins and tubulin during cell cycle progression in synchronized Vicia faba root meristem cells.

MPM-2 antibody reacts with a subset of mitotic phosphoproteins. We followed localization of MPM-2 immunoreactive material and localization of microtubules during cell cycle progression in a highly synchronous population of Vicia faba root meristem cells and isolated nuclei. The MPM-2 antibody labelling showed significant cell cycle dependence. MPM-2 nuclear reactivity was weak and homogeneous in G1 and S phase of the cell cycle and became stronger and heterogeneous during G2, resembling staining of the nuclear matrix, with maximum staining at the G2/M interface. Similarly the staining intensity of nucleoli increased from late G1 phase to nucleoli dispersion in early prophase. During mitosis MPM-2 immunoreactivity was associated with spindle configurations and the brightest signal was localized in kinetochores from prophase to metaphase.

Antibodies, Monoclonal↗

PubMed2002

Competence of oat ( Avena sativa L.) shoot apical meristems for integrative transformation, inherited expression, and osmotic tolerance of transgenic lines containing hva1.

Three oat ( Avena sativa L.) cultivars have been successfully transformed using an efficient and reproducible in vitro culture system for differentiation of multiple shoots from shoot apical meristems. The transformation was performed using microprojectile bombardment with two plasmids (pBY520 and pAct1-D) containing linked ( hva1-bar) and non-linked ( gus) genes. The hva1 and bar genes cointegrated with a frequency of 100% as expected, and 61.6% of the transgenic plants carried all three genes. Molecular and biochemical analyses in R0, R1 and R2 progenies confirmed stable integration and expression of all transgenes. Localization of the GUS protein in R0 and R1 plants revealed that high-expression of gus occurred in vascular tissues and in the pollen grains of mature flowers. The constitutive expression of HVA1 protein was observed at all developmental stages of transgenic plants, and was particularly stronger during the early seedling stages. R2 progeny of five independent transgenic lines was tested in vitro for tolerance to osmotic (salt and mannitol) stresses. As compared to non-transgenic control plants, transgenic plants maintained a higher growth and showed significantly ( P < 0.05) increased tolerance to stress conditions. Less than 10% of transgenic plants showed symptoms of wilting or death of leaves and, when these symptoms present were delayed in transgenic plants as compared to 80% of non-transgenic plants, either wilted or died. These symptoms confirmed the increased in vitro tolerance in hva1-expressing transgenic plants to non-transgenic plants, providing strong evidence that the HVA1 protein may play an important role in the protection of oats against salinity and possible water-deficiency stress conditions.

Journal Article↗

PubMed2003

Fertile transgenic pearl millet [ Pennisetum glaucum (L.) R. Br.] plants recovered through microprojectile bombardment and phosphinothricin selection of apical meristem-, inflorescence-, and immature embryo-derived embryogenic tissues.

Pearl millet [ Pennisetum glaucum (L.) R. Br.] is a drought-tolerant cereal crop used for grain and forage. Novel traits from outside of the gene pool could be introduced provided a reliable gene-transfer method were available. We have obtained herbicide-resistant transgenic pearl millet plants by microprojectile bombardment of embryogenic tissues with the bar gene. Embryogenic tissues derived from immature embryos, inflorescences and apical meristems from diploid and tetraploid pearl millet genotypes were used as target tissues. Transformed cells were selected in the dark on Murashige and Skoog medium supplemented with 2 mg/l 2,4-D and 15 mg/l phosphinothricin (PPT). After 3-10 weeks in the dark, herbicide-resistant somatic embryos were induced to germinate on MS medium containing 0.1 mg/l thidiazuron and 0.1 mg/l 6-benzylaminopurine. Plants were transferred to the greenhouse after they were rooted in the presence of PPT and had passed a chlorophenol red assay (the medium turned from red to yellow). Transgenic plants were recovered from bombardments using intact pAHC25 plasmid DNA, a gel-purified bar fragment, or a mixture of pAHC25 plasmid or bar fragment and a plasmid containing the enhanced green fluorescent protein ( gfp) gene (p524EGFP.1). Analyses by the polymerase chain reaction, Southern blot hybridization, GFP expression, resistance to herbicide application, and segregation of the bar and gfp genes confirmed the presence and stable integration of the foreign DNA. Transformed plants were recovered from all three explants, although transformation conditions were optimized using only the tetraploid inflorescence. Time from culture initiation to rooted transgenic plant using the tetraploid inflorescence ranged from 3-4 months. Seven independent DNA/gold precipitations were used to bombard 52 plates, 29 of which produced an average of 5.5 herbicide-resistant plants per plate. The number of herbicide-resistant plants recovered per successful bombardment ranged from one to 28 and the frequency of co-transformation with gfp ranged from 5% to 85%.

Acetyltransferases↗

PubMed2000

Clonal Analysis Provides Evidence for Transient Initial Cells in Shoot Apical Meristems of Seed Plants.

Drift of mutated sectors in sectorial or mericlinal plant chimeras has been interpreted as indirect evidence of initial impermanence at the apex. However, the same effect may result from mutation in noninitial cells positioned close to the vertex of the apical dome. Clonal analysis of the cell packets present in the superficial layer of spruce and magnolia apices provided the library of patterns suggesting that the position and the number of initial cells, and in some cases also the meristem axis inclination, may change over time. Multicellular clones originating from a single cell have been found in the geometric center of some apices, whereas in other apices the cellular center (where three or four clonal borders meet) did not correspond to the geome

Journal Article↗

PubMed2002

Embryonic shoot apical meristem formation in higher plants.

The shoot apical meristem (SAM) is essential for organ formation in higher plants. How the SAM is formed during plant development is poorly understood, however. In this review, we focus on several recent studies that provide new insights into the mechanism of SAM formation during embryogenesis. Recently, positive and negative regulators of the class I KNOX genes, which are thought to be necessary for SAM formation, have been identified; the Arabidopsis CUP-SHAPED COTYLEDON ( CUC) genes are required for the expression of a class I KNOX gene, SHOOT MERISSTEMLES( STM) during embryogenesis, and the Arabidopsis ASYMMETRIC LEAVES1 ( AS1), AS2, and several other genes negatively regulate KNOX gene expression in cotyledon primordia. Also, several genes that are involved in the formation of the adaxial-abaxial axis of cotyledons seem to regulate embryonic SAM formation.

Journal Article↗

PubMedDate not supplied

Heat shock protection against induction of chromatid aberrations is dependent on the time span between heat shock and clastogen treatment of Vicia faba root tip meristem cells.

Variation of the time span between heat shock (hs) and clastogen treatment of V. faba root tip meristems showed that hs protection is a very quick response (effective after less than 10 min) and lasting for up to 240 min in the case of induction of chromatid aberrations by maleic hydrazide (MH). Analogous protective responses are significantly slower and shorter when TEM is used for aberration induction. This, together with absence of 'clastogenic cross-adaptation' to these agents and differential effects of benzamide (BA, an inhibitor of poly-ADP-ribosylation) pretreatment before hs on hs protection, suggests that hs before clastogen treatment triggers at least 2 clastogen-specific, protective functions which eventually result in protection against these 2 clastogens.

Chromosome Aberrations↗

PubMed1990

Involvement of phytochelatins in NiCl2-triggered protection against induction of chromatid aberrations by TEM and MH in Vicia faba root tip meristems?

Conditioning treatment of Vicia faba root tip meristem cells with NiCl2 prior to challenge treatment with triethylenemelamine (TEM) or maleic hydrazide (MH) triggered protective functions against both these clastogens, i.e., resulted in a significantly reduced yield of metaphases with chromatid aberrations. Protection was prevented by pretreatment with buthionine sulfoximine (BSI), an inhibitor of the synthesis of plant phytochelatins (PCs), indicating that the NiCl2-triggered PC synthesis may be involved in the protective functions induced by NiCl2 conditioning treatment. BSI (instead of NiCl2) conditioning treatment triggered protection against MH but not against TEM.

Buthionine Sulfoximine↗