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At least 595 records · Page 33Linked to original sources
PubMed2004

Ultrastructural and autoradiographic studies of the role of nucleolar vacuoles in soybean root meristem.

Ultrastructural and autoradiographic studies of nucleoli in soybean root meristematic cells in seedlings: (1) grown for 3 days at 25 degrees C (control), (2) grown for three days at 25 degrees C and for 4 days at 10 degrees C, and (3) grown as in (2) and recovered for 1 day at 25 degrees C were carried out. Control nucleoli had dense structure and a few small nucleolar vacuoles. Chilled plant nucleoli had less dense structure and no vacuoles. Nucleoli of plants recovered at 25 degrees C had big nucleolar vacuoles. In autoradiograms of squashed preparations, the labeling of nucleoli and cytoplasm after 20-min incubation in 3H-uridine was 5- and 6-fold stronger, respectively, in control than in chilled roots. Following recovery, the labeling of nucleoli and cytoplasm was much stronger than after chilling or even than in control roots. After 80-min postincubation in non-radioactive medium, average labeling of particular areas of cells was the highest in recovered plants which indicated intensification of rRNA synthesis, maturation and transport into cytoplasm resulting from the resumption of optimal conditions which was correlated with the appearance of big nucleolar vacuoles. In autoradiograms of semi-thin sections from roots of seedlings chilled for 4 days then recovered and incubated for 20 min in 3H-uridine, practically only extravacuolar parts of nucleoli were labeled. After 80-min postincubation, the labeling of nucleolar vacuoles was observed. Thus, during postincubation the labeled molecules were translocated from the nucleolar periphery into nucleolar vacuoles in cells where intensive transport of these molecules to the cytoplasm takes place. On the basis of these results, a hypothesis has been put forward that nucleolar vacuoles may be involved in the intensification of pre-ribosome transport outside nucleolus.

Autoradiography↗
PubMed2006

In vivo studies on the effect of Ocimum sanctum L. leaf extract in modifying the genotoxicity induced by chromium and mercury in Allium root meristems.

In vivo cytogenetic assay in Allium cepa root tip cells has been carried out to detect the modifying effect of Ocimum sanctum aqueous leaf extract against chromium (Cr) and mercury (Hg) induced genotoxicity. It was observed that the roots post-treated with the leaf extract showed highly significant (p < 0.001) recovery in mitotic index (MI) and chromosomal aberrations (CA) when compared to pre-treated (Cr/Hg) samples and the lower doses of the leaf extract were found to be more effective than higher doses. The present study reveals that the Ocimum sanctum leaf extract possesses the protective effect against Cr/Hg induced genetic damage.

Allium↗
PubMedDate not supplied

[Cytogenetic analysis of first two mitoses in the root meristem of stored for a prolonged time period Crepis tectorum seeds subjected to chronic irradiation in the 30-kilometer zone of the accident at the Chernobyl Atomic Power Plant].

Seeds of Crepis tectorum natural populations 1 and 3 subjected to chronic irradiation in 1986 during 4 months in 30-kilometers zone of Chernobyl were stored for 6 years in a laboratory. In 1993 a method of continuous germination of seeds in 0.01% colchicin solution was used and an analysis of chromosome aberrations in the first tetraploid cells was made as it was done in 1987 just after finishing of a dormant period of seeds. By extrapolation from the data obtained by studying cells of the second colchicine mitosis to the cells of the previous mitosis from which they derived it was shown that the frequency of chromatid type aberrations in the early dividing cells after 6 year storage remained at the level which was observed just after finishing of a dormant period. This fact supports our previous proposition that chromatid aberrations observed in early dividing cells were probably induced by the incorporated long term radioactive products during seed germination, but not during seed storage.

Magnoliopsida↗
PubMed1994

Meristem-specific gene expression directed by the promoter of the S-phase-specific gene, cyc07, in transgenic Arabidopsis.

A genomic clone for the cyc07 gene, which is expressed specifically at the S phase during the cell cycle in synchronous cultures of periwinkle (Catharanthus roseus) cells, was isolated. Determination of the nucleotide sequence of the clone revealed that the cyc07 gene consists of seven exons separated by six introns. Genomic Southern analysis indicated that the cyc07 gene is present as a single copy per haploid genome in periwinkle. Expression of related genes was detected in a wide range of other plants. Transgenic Arabidopsis plants were generated that expressed the gene for beta-glucuronidase (GUS) under the control of the promoter of the cyc07 gene. The tissue-specific pattern of expression directed by the promoter was investigated by analysis of GUS activity. Histochemical tests demonstrated that 589 bp of the 5'-upstream sequence of the cyc07 gene could direct specifical expression of the GUS reporter gene in meristematic tissues in transgenic plants. The spatial pattern of expression directed by the promoter was closely correlated with meristematic activity and cell proliferation, suggesting an association between the function of the cyc07 gene and cell proliferation.

Amino Acid Sequence↗
PubMed1994

Expression in different populations of cells of the root meristem is controlled by different domains of the rolB promoter.

Selective gene expression in different populations of cells of the root apex of transgenic tobacco could be evidenced by means of GUS constructs with deletions of the rolB promoter and fusions with the CaMV 35S minimal promoter. Five regulatory regions have been broadly identified in the rolB 5' non-coding region. The presence of all five domains (A to E) directs gene expression in the root cap, in the protoderm and in the different tissues within the root meristematic region: the dermatocalyptrogen, the cortex and the vascular cylinder. Deletion of domain A (-623 to -471) selectively suppresses expression in non-meristematic cells, i.e. the root cap and the protoderm. Deletion of either domain B (-341 to -306) or E (80 bp around the TATA box) causes loss of expression in all cells of the root apex: constructs C + D + E, B + C + D, B + C are inactive. Domain D (70 bp around the CAAT box) is necessary for gene expression in the dermatogen and in meristematic cells of the cortex but not in the innermost meristematic layer: construct B + C + E is active only in vascular meristematic cells. Domain C (-216 to -158) seems to have a double regulatory role as construct B + E is no longer expressed in meristematic cells of the vascular cylinder but is very active in the protoderm. Constructs allowing gene expression in meristematic cells are also inducible by auxin in leaf protoplasts, while activation of the regulatory elements necessary for gene expression in the non-meristematic cells of the root apex do not seem to depend upon the hormone. The connection between auxin induction and meristematic expression is discussed.

Enzyme Induction↗
PubMed2001

Cell division patterns of the protoderm and root cap in the "closed" root apical meristem of Arabidopsis thaliana.

The peripheral root cap and protoderm in Arabidopsis thaliana are organized into modular packets of cells derived from formative T-divisions of the root cap/protoderm (RCP) initials and subsequent proliferative divisions of their daughter cells. Each module consists of protoderm and peripheral root cap packets derived from the same periclinal T-division event of an RCP initial. Anatomical analyses are used to interpret the history of extensively coordinated cell divisions producing this modular construction. Within a given layer of root cap, the columella and RCP initials divided in a centrifugal sequence from the innermost columella initials toward the RCP initials. All RCP initials in the lineages around the circumference of the root divided nearly simultaneously in "waves" to form one module prior to the next wave of initial divisions forming a younger module. The peripheral root cap and protoderm packets within each module completed four rounds of proliferative divisions in the axial plane to produce, on average, 16 cells per packet in the basalmost modules in axial view. Peripheral root cap and protoderm cells predominantly in the T-type (trichoblast) lineages also underwent radial divisions as they were displaced basipetally. The regularity in the cellular pattern within the modules suggests a timing mechanism controlling highly coordinated cell division in the initials and their daughter cells.

Arabidopsis↗
PubMed2002

Cytogenetic damage in shallot ( Allium cepa) root meristems induced by oil industry "high-density brines".

Saturated water solutions of calcium chloride, calcium bromide (densities 1.30 kg x dm(-3) and 1.61 kg x dm(-3), respectively) and their 1:1 mixture have been commonly used as oil industry "high-density brines." In our experiment they were added to tap water in amounts appropriate to achieve concentrations of 0.025, 0.05, 0.075, and 0.1 mol x dm(-3) to study their cytotoxic effect on the root tip cells of shallot ( Allium cepa L. var. ascalonicum). All tested solutions in concentrations of 0.075 and 0.1 mol x dm(-3) caused significant inhibition of shallot root growth. CaBr (2) showed this effect in concentration 0.05 mol x dm(-3). The investigated solutions in all concentrations applied decreased mitotic activity in root tip cells. The most of mitotic abnormalities were the consequence of spindle failure and chromosome stickiness. Furthermore, the cell microtubules were investigated by indirect immunofluorescence to confirm that most abnormalities observed were the consequence of spindle failure. The present study, as well as previously done Lemna tests and Chlorella tests showed that investigated samples have certain effects on plants, so constant control of their presence in the environment is needed.

Bromides↗
PubMed2005

OsMADS22, an STMADS11-like MADS-box gene of rice, is expressed in non-vegetative tissues and its ectopic expression induces spikelet meristem indeterminacy.

We report the cDNA sequence and gene expression patterns of OsMADS22, a novel member of the STMADS11-like family of MADS-box genes, from rice. In contrast to previously reported STMADS11-like genes, whose expression is detected in vegetative tissues, OsMADS22 is mainly expressed during embryogenesis and flower development. In situ hybridization analysis revealed that OsMADS22 expression is localized in the L1 layer of embryos and in developing stamen primordia. Ectopic expression of OsMADS22 in transgenic rice plants resulted in aberrant floral morphogenesis, characterized by a disorganized palea, an elongated glume, and a two-floret spikelet. The results are discussed in terms of rice spikelet development and a novel non-vegetative role for a STMADS11-like gene.

Base Sequence↗