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At least 469 records · Page 26Linked to original sources
PubMed2002

Immuno-cytochemical localization of indole-3-acetic acid during induction of somatic embryogenesis in cultured sunflower embryos.

Immature zygotic embryos of sunflower (Helianthus annuus L.) produce somatic embryos when cultured on medium supplemented with a cytokinin as the sole source of exogenous growth regulators. The timing of the induction phase and subsequent morphogenic events have been well characterized in previous work. We address here the question of the role of endogenous indole-3-acetic acid (IAA), since auxins are known to have a crucial role in the induction of somatic embryogenesis in many other culture and regeneration systems. The fact that in the sunflower system no exogenous auxin is required for the induction of somatic embryos makes this system very suitable for the study of the internal dynamics of IAA. We used an immuno-cytochemical approach to visualize IAA distribution within the explants before, during and after the induction phase. IAA accumulated transiently throughout cultured embryos during the induction phase. The detected signal was not uniform but certain tissues, such as the root cap and the root meristem, accumulated IAA in a more pronounced manner. IAA accumulation was not restricted to the reactive zone but the kinetics of endogenous variations strikingly mimic the pulse of IAA that is usually provoked by exogenous IAA application. The direct evidence presented here indicates that an endogenous auxin pulse is indeed among the first signals leading to the induction of somatic embryogenesis.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1997

Flow cytometry, sorting and immunocharacterization with proliferating cell nuclear antigen of cycling and non-cycling cells in synchronized pea root tips.

In the 3-d-old 2-mm root tip of Pisum sativum L. cv. Lincoln the percentage of actively proliferating cells is estimated to be 70%. The remaining cells are non-cycling and arrested with 2C and 4C DNA content in G0 and in G2Q, respectively. In this work we studied the kinetic significance of these quiescent cells, using the sorting capabilities of flow cytometry and immunofluorescence techniques to detect the proliferation marker PCNA (proliferating cell nuclear antigen) inside cells within the different cell-cycle compartments. While in animal cells, PCNA is present at a high level only in actively proliferating cells, in 3-d-old pea root tips 95% of the cells are PCNA-positive. After flow cytometry and sorting of pea non-cycling nuclear populations, all G2Q nuclei appeared strongly PCNA-positive, indicating that these cells had recently left the cell cycle. By contrast, most G0 nuclei showed a low level of PCNA immunofluorescence intensity, as measured by image analysis, with about 25% of the nuclei being PCNA-negative. This small percentage was found to correspond to root cap cells, as could be observed in the root tip section. These are the only cells in the root apical region which are fully differentiated and which, therefore, lack the competence to enter the cell cycle. In contrast, the more or less PCNA-positive G0 nuclei could represent a kinetically heterogeneous population of cells competent to proliferate, but which have either recently left the cell cycle or are progressing to the G0-G1 transition.

Cell Cycle↗
PubMed1999

Effect of pectin methylesterase gene expression on pea root development.

Expression of an inducible gene with sequences common to genes encoding pectin methylesterase (PME) was found to be tightly correlated, both spatially and temporally, with border cell separation in pea root caps. Partial inhibition of the gene's expression by antisense mRNA in transgenic pea hairy roots prevented the normal separation of root border cells from the root tip into the external environment. This phenotype was correlated with an increase in extracellular pH, reduced root elongation, and altered cellular morphology. The translation product of the gene exhibited PME activity in vitro. These results are consistent with the long-standing hypothesis that the demethylation of pectin by PME plays a key role in cell wall metabolism.

Amino Acid Sequence↗
PubMed2000

[Effects of IAA and stimulated microgravity on formation of adventitious roots of Chinese cabbage].

Under the induction of indole-3-acetic acid (IAA), adventitious roots were differentiated on hypocotyl segments derived from seedlings of Chinese cabbage (Brassica campestris spp. pekinensis). IAA at concentration of 0.4-1.0 mg/L in solid MS medium incited many adventitious roots on hypocotyl segments. The earliest anatomic changes were observed on cut surface of hypocotyl segments under optical microscope 24 hours after IAA treatment: cytoplasmic and nuclear density became higher in a few of parenchytmatous cells adjacent to phloem in tissue of pericycle, followed by cell divisions. Lately, the dividing cells expanded and developed into root primordium from which root cap was differentiated. After five days, most roots protruded through hypocotyl cortex and appeared just below the cut surface. The rooting capacity of the segments derived from three regions of each hypocotyl was different. High level of IAA modified the polarity of root formation on segment inserted upside down and sucrose increased the function of IAA. Additionally, microgravity did not significantly change the rooting polarity under the condition of stimulated microgravity, but it increased the competence of explants to IAA treatment. The results presented here provided an experimental system for further investigation of molecular events associated with adventitious root initiation.

Brassica↗
PubMed1976

Autoradiographic and ultrastructural study of Cucurbita pepo root cells during their growth and differentiation.

Cortex cells of the root meristem of Cucurbita pepo (0.0-0.5 mm from the cap junction), in the 3-4, 5-6 and 7-8 mm segments above the root tip, and the cells of the first three layers of lateral part of root cap were the object of the present study. The volume of cortex cells increases more than 20 times in the 7-8 mm segment as compared with meristematic cells, and the volume of cytoplasm about sevenfold. The largest increment of the cytoplasmic volume occurs between 0.5-6.0 mm. In consecutive root segments the sustained increase of the volume of nuclei takes place. By applying autoradiography the following processess have been investigated: DNA synthesis (3H thymidine uptake), template activity of DNA (3H actinomycin D(3H AMD)-binding), RNA synthesis (3H uridine incorporation), and protein synthesis (3H leucine). In the root cap cells and in segments where meristematic activity is over, DNA is replicated by endomitosis. On the basis of nuclear labelling it appears that nuclei in the 3-4 mm segment reach 4C ploidy state, but in the 7-8 mm segment half of the nuclei reach the 8C ploidy state. Most of the root cap cells are 4C, the remaining cells are 8C. Considering the uptake of 3H thymidine into nucleoli one may suppose that in the root cap cells nucleolar DNA is underreplicated, and to a lesser degree in 5-6 and 7-8 mm segments, while in 3-4 mm segment DNA is overreplicated as compared to meristem cells. Measurements of nucleolar volume, 3H uridine uptake, 3H AMD binding and quantity of granular component, indicate that the most noticeable nucleolar activity takes place in meristematic zone and in root parts showing the highest increase of cytoplasmic volume (3-4 and 5-6 mm segments). 3H leucine is still incorporated intensely into 7-8 mm segment, in which the concentration of ribosomes is low, however they are present in the form of polysomes. Comparison of 3H thymidine uptake into nuclear DNA with 3H AMD binding and 3H uridine incorporation into nuclei indicates that endomitotic DNA replication results in an increase of DNA template activity in root cap cells as well as in 3-4 and 5-6 mm segments; in the 7-8 mm segment binding of 3H AMD slightly decreases, while 3H uridine incorporation is considerably reduced. Divergence between the ploidy state, 3H AMD binding and 3H uridine incorporation can be due to the increment of the condensed chromatin area in differentiated cells. Plastids and mitochondria reach full maturity in 3-4 mm segment. The increasing volume density of ER and diminishing volume density of Golgi structures is accompanied by differentiation of cortex cells.

Cell Differentiation↗
PubMed2004

Licochalcone-A, a novel flavonoid isolated from licorice root (Glycyrrhiza glabra), causes G2 and late-G1 arrests in androgen-independent PC-3 prostate cancer cells.

Licochalcone (LA) is a novel estrogenic flavonoid isolated from PC-SPES composition herb licorice root that was reported to show significant antitumor activity in various malignant human cell lines. To better understand its anti-CaP activities, we have investigated LA-elicited growth control and induction of apoptosis using androgen-independent p53-null PC-3 prostate cancer cells. LA induced modest level of apoptosis but had more pronounced effect on cell cycle progression arresting cells in G2/M, accompanied by suppression of cyclin B1 and cdc2. It also inhibited phosphorylation of Rb, specifically phosphorylation of S780 with no change of phosphorylation status of T821, decreased expression of transcription factor E2F concurrent with reduction of cyclin D1, down-regulation of CDKs 4 and 6, but increased cyclin E expression. These findings provide mechanistic explanation for LA activity and suggest that it may be considered as a chemopreventive agent and its anticancer properties should be further explored.

Androgens↗
PubMed1998

Characterization of LeMir, a root-knot nematode-induced gene in tomato with an encoded product secreted from the root.

A tomato gene that is induced early after infection of tomato (Lycopersicon esculentum Mill.) with root-knot nematodes (Meloidogyne javanica) encodes a protein with 54% amino acid identity to miraculin, a flavorless protein that causes sour substances to be perceived as sweet. This gene was therefore named LeMir (L. esculentum miraculin). Sequence similarity places the encoded protein in the soybean trypsin-inhibitor family (Kunitz). LeMir mRNA is found in root, hypocotyl, and flower tissues, with the highest expression in the root. Rapid induction of expression upon nematode infection is localized to root tips. In situ hybridization shows that LeMir is expressed constitutively in the root-cap and root-tip epidermis. The LeMir protein product (LeMir) was produced in the yeast Pichia pastoris for generation of antibodies. Western-blot analysis showed that LeMir expression is up-regulated by nematode infection and by wounding. LeMir is also expressed in tomato callus tissue. Immunoprint analysis revealed that LeMir is expressed throughout the seedling root, but that levels are highest at the root/shoot junction. Analysis of seedling root exudates revealed that LeMir is secreted from the root into the surrounding environment, suggesting that it may interact with soil-borne microorganisms.

Amino Acid Sequence↗
PubMed2002

MADS-box gene expression in lateral primordia, meristems and differentiated tissues of Arabidopsis thaliana roots.

Although MADS-box genes involved in flower and fruit development have been well characterized, the function of MADS-box genes expressed in vegetative structures has yet to be explored. At least seven members of this family are grouped in clades of genes that are preferentially expressed in roots of Arabidopsis thaliana (L.) Heynh.. We report here the cloning of the AGL21 MADS-box gene, which belongs to the ANR1 clade, and the mRNA in situ expression patterns of this and two other root MADS-box genes. AGL17 appears to be a lateral root cap marker in the root tip, and towards the elongation zone this gene is expressed in the epidermal cells. AGL21 is highly expressed in lateral root primordia and it has a punctate expression pattern in the primary root meristem. AGL12 also has a punctate expression pattern in the primary root meristem. AGL12 and AGL21 are also expressed in the central cylinder of differentiated roots and both are expressed in developing embryos. This study, combined with previous phylogenetic analyses, indicates that these MADS-box genes may play distinct regulatory roles during root development.

Arabidopsis↗
PubMed1990

Influence of electrical fields and asymmetric application of mucilage on curvature of primary roots of Zea mays.

Primary roots of Zea mays cv. Yellow Dent growing in an electric field curve towards the anode. Roots treated with EDTA and growing in electric field do not curve. When root cap mucilage is applied asymmetrically to tips of vertically-oriented roots, the roots curve toward the mucilage. Roots treated with EDTA curve toward the side receiving mucilage and toward blocks containing 10 mM CaCl2, but not toward "empty" agar blocks or the cut surfaces of severed root tips. These results suggest that 1) free calcium (Ca) is necessary for root electrotropism, 2) mucilage contains effector(s) that induce gravitropiclike curvature, and 3) mucilage can replace gravitropic effectors chelated by EDTA. These results are consistent with the hypothesis that the downward movement of gravitropic effectors to the lower sides of tips of horizontally-oriented roots occurs at least partially in the apoplast.

Biological Transport↗
PubMed2005

Root gravitropism requires lateral root cap and epidermal cells for transport and response to a mobile auxin signal.

Re-orientation of Arabidopsis seedlings induces a rapid, asymmetric release of the growth regulator auxin from gravity-sensing columella cells at the root apex. The resulting lateral auxin gradient is hypothesized to drive differential cell expansion in elongation-zone tissues. We mapped those root tissues that function to transport or respond to auxin during a gravitropic response. Targeted expression of the auxin influx facilitator AUX1 demonstrated that root gravitropism requires auxin to be transported via the lateral root cap to all elongating epidermal cells. A three-dimensional model of the root elongation zone predicted that AUX1 causes the majority of auxin to accumulate in the epidermis. Selectively disrupting the auxin responsiveness of expanding epidermal cells by expressing a mutant form of the AUX/IAA17 protein, axr3-1, abolished root gravitropism. We conclude that gravitropic curvature in Arabidopsis roots is primarily driven by the differential expansion of epidermal cells in response to an influx-carrier-dependent auxin gradient.

Arabidopsis↗
PubMed2001

Expression studies on AUX1-like genes in Medicago truncatula suggest that auxin is required at two steps in early nodule development.

Medicago truncatula contains a family of at least five genes related to AUX1 of Arabidopsis thaliana (termed MtLAX genes for Medicago truncatula-like AUX1 genes). The high sequence similarity between the encoded proteins and AUX1 implies that the MtLAX genes encode auxin import carriers. The MtLAX genes are expressed in roots and other organs, suggesting that they play pleiotropic roles related to auxin uptake. In primary roots, the MtLAX genes are expressed preferentially in the root tips, particularly in the provascular bundles and root caps. During lateral root and nodule development, the genes are expressed in the primordia, particularly in cells that were probably derived from the pericycle. At slightly later stages, the genes are expressed in the regions of the developing organs where the vasculature arises (central position for lateral roots and peripheral region for nodules). These results are consistent with MtLAX being involved in local auxin transport and suggest that auxin is required at two common stages of lateral root and nodule development: development of the primordia and differentiation of the vasculature.

Amino Acid Sequence↗
PubMed1997

Cytoplasmic free Ca2+ in Arabidopsis roots changes in response to touch but not gravity.

Changes in cytoplasmic Ca2+ concentration ([Ca2+]i) have been proposed to be involved in signal transduction pathways in response to a number of stimuli, including gravity and touch. The current hypothesis proposes that the development of gravitropic bending is correlated with a redistribution of [Ca2+]i in gravistimulated roots. However, no study has demonstrated clearly the development of an asymmetry of this ion during root curvature. We tested this hypothesis by quantifying the temporal and spatial changes in [Ca2+]i in roots of living Arabidopsis seedlings using ultraviolet-confocal Ca(2+)-ratio imaging and vertical stage fluorescence microscopy to visualize root [Ca2+]i. We observed no changes in [Ca2+]i associated with the graviresponse whether monitored at the whole organ level or in individual cells in different regions of the root for up to 12 h after gravistimulation. However, touch stimulation led to transient increases in [Ca2+]i in all cell types monitored. The increases induced in the cap cells were larger and longer-lived than in cells in the meristematic or elongation zone. One millimolar La3+ and 100 microM verapamil did not prevent these responses, whereas 5 mM EGTA or 50 microM ruthenium red inhibited the transients, indicating an intracellular origin of the Ca2+ increase. These results suggest that although touch responses of roots may be mediated through a Ca(2+)-dependent pathway, the gravitropic response is not associated with detectable changes in [Ca2+]i.

Arabidopsis↗
PubMed1998

Developmentally regulated organ-, tissue-, and cell-specific expression of calmodulin genes in common wheat.

Recently, we reported on the characterization of the calmodulin (CaM) gene family in wheat [44]. We classified wheat CaM genes into four subfamilies (SFs) designated SF-1 to SF-4, each representing a series of homoeoallelic loci on the homoeologous chromosomes of the three genomes of common wheat. Here we studied the expression of these wheat CaM genes in the course of wheat development. Northern blot analysis using SF-specific probes revealed differences in SF expression levels in different organs and stages of development. Subsequently, cell-specific expression of CaM SFs was investigated by in situ RNA hybridization. In developing seeds, all CaM SFs showed highest expression in the embryo and less in the aleurone and in the starchy endosperm. In primary roots, all four CaM SFs were expressed in the root cap, meristematic regions and in differentiating cells. During development of the roots, expression gradually decreased. The wheat glutenin gene, which was used as a control throughout our experiments, was found to be expressed in the starchy endosperm but not in the aleurone, embryos or vegetative tissues. In stems, at advanced stages of growth, differences in cell-specific expression of CaM SFs were found. For example, SF-2 was highly expressed in differentiating phloem fibers. Thus, CaM genes in common wheat exhibit a developmentally regulated organ-, tissue-, cell- and SF-specific expression patterns.

Blotting, Northern↗
PubMed2006

Hierarchical assembly of the siliceous skeletal lattice of the hexactinellid sponge Euplectella aspergillum.

Despite its inherent mechanical fragility, silica is widely used as a skeletal material in a great diversity of organisms ranging from diatoms and radiolaria to sponges and higher plants. In addition to their micro- and nanoscale structural regularity, many of these hard tissues form complex hierarchically ordered composites. One such example is found in the siliceous skeletal system of the Western Pacific hexactinellid sponge, Euplectella aspergillum. In this species, the skeleton comprises an elaborate cylindrical lattice-like structure with at least six hierarchical levels spanning the length scale from nanometers to centimeters. The basic building blocks are laminated skeletal elements (spicules) that consist of a central proteinaceous axial filament surrounded by alternating concentric domains of consolidated silica nanoparticles and organic interlayers. Two intersecting grids of non-planar cruciform spicules define a locally quadrate, globally cylindrical skeletal lattice that provides the framework onto which other skeletal constituents are deposited. The grids are supported by bundles of spicules that form vertical, horizontal and diagonally ordered struts. The overall cylindrical lattice is capped at its upper end by a terminal sieve plate and rooted into the sea floor at its base by a flexible cluster of barbed fibrillar anchor spicules. External diagonally oriented spiral ridges that extend perpendicular to the surface further strengthen the lattice. A secondarily deposited laminated silica matrix that cements the structure together additionally reinforces the resulting skeletal mass. The mechanical consequences of each of these various levels of structural complexity are discussed.

Animals↗
PubMed2006

Reduction of vitrification in in vitro raised shoots of Chlorophytum borivilianum Sant. & Fernand., a rare potent medicinal herb.

Reduction of vitrification in in vitro raised shoots derived from shoot bases and immature floral buds along with inflorescence axis used as explants of C. borivilianum, a rare medicinal herb is described. Shoot multiplication was obtained on MS medium with 2 mg l(-1) benzylaminopurine (BAP) + 0.1 mg l(-1) indole-3-butyric acid (IBA) and MS medium with 2 mg l(-1) kinetin (Kin) + 0.1 mg l(-1) 2,4-dichlorophenoxy acetic acid (2,4-D) from shoot bases and inflorescence axis respectively. Best multiplication rates were obtained from both the explants on MS medium with 2 mg l(-1) BAP. Vitrification of shoots in cultures appeared during the multiplication stage. Culture bottles with aerated caps reduced the vitrification to 80%. Reduction of BAP concentration from 2 mg l(-1) to zero during subsequent subcultures also minimized vitrification. Use of 0.5-2 mg l(-1) Kin produced healthy shoots when compared to BAP. In vitro raised shoots rooted on Knop salts containing iron and vitamins of MS medium, 2 mg l(-1) IBA and 0.1% activated charcoal. About 80% plantlets survived upon soil transfer. Scanning electron microscopic and image analyzer studies reveal the morphological structural differences between the leaves of normal and vitrified plantlets.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2002

[Medical consultation dynamics in Japanese cedar pollinosis patients at an office building clinic in central Tokyo].

To clarify medical consultation dynamics in Japanese cedar pollinosis patients visiting an office building clinic in an office block in central Tokyo, we surveyed number of patient at a private ENT clinic in Chiyoda-ku, Tokyo, during the Japanese cedar pollen season from 1990 to 1999. Based on questionnaires and CAP RAST tests in 1995, we studied the profiles of Japanese cedar pollinosis patients and determined positive rates of noncedar antigens. The gender ratio in 1995 was 674 men versus 501 women, most frequently men in their 40s and women in their 20s. Of these, 79.2% worked in Chiyoda-ku and Chuo-ku, but only 1.9% lived in these districts. Positive rates of noncedar antigens in 232 who received simultaneous CAP RAST tests were 64.7% for Japanese cypress, 38.3% for house dust, 35.3% for Dermatophagoides pteronyssinus, 34.4% for Epidermoptidae spp, 19.8% for mixed grasses, and 10.3% for mixed weeds (asteraceous plants). Patients positive for cedar alone were 19.0% and positive for both cedar and cypress but negative for other antigens were 23.3%; about 60% of these were suspected of multiple sensitization to antigens other than cedar and cypress. The number of pollens and patients were summarized weekly and compared. Those paying a first visit were peaked with an increase in pollen in the first week of March almost every year; second visits peaked 1 or 2 weeks later than the first visit. Little increase in first visit was noted even with increasing pollen dissemination from the latter half of March. The relationship between the number of pollen and patients each year from 1990 to 1999 correlated highly with the linear regression equation y = 0.1005x + 547.07 with R2 = 0.7562. The relationship between square roots of the number of pollen and patients each year for 5 year from 1995 to 1999 correlated very highly with the linear regression equation y = 11.167x + 376.72 with R2 = 0.9941. We concluded that the number of patients may be predicted with substantially higher accuracy based on the estimated amount of pollen in a given year.

Adult↗
PubMed1978

The structure and function of glycoproteins synthesized during slime-polysaccharide production by membranes of the root-cap cells of maize (Zea mays).

The synthesis of the maize root slime polysaccharides was investigated by using [1-3H]-fucose as a marker for slime production. Three fractions were separated by centrifugation in a CsCl density gradient. Two of these were glycoproteins and occurred within the membranes of the cells of the root tip; the third was the slime polysaccharides. Radioactive pulse-chase experiments showed that the glycoproteins were precursors of the slime polysaccharides, and the carbohydrate portion of the glycoproteins had a similar composition to that of the free slime. The linkage between the protein and the carbohydrate of one of the glycoproteins was shown to be a xylose-threonine bond. It is postulated that the slime polysaccharides are synthesized and transported on proteins within the membrane system of the root tip.

Cell Membrane↗
PubMed1996

Roles of the 35S promoter and multiple overlapping domains in the pathogenicity of the pararetrovirus cauliflower mosaic virus.

Elements associated with the 35S promoter involved in generating the pregenomic RNA (35S RNA) of the pararetrovirus cauliflower mosaic virus have been extensively studied in heterologous systems, but little is known about their role in viral pathogenicity. To investigate these elements, premature termination codons were progressively inserted into the 3' end of the adjacent gene VI to dissect it from colinear 35S enhancer sequences. The ability to cause a systemic infection in plants was retained with loss of up to 40 amino acids from the gene VI polypeptide, but truncations into a putative zinc finger proved lethal. In the 35S promoter, removal of the TATA box also abolished infectivity. However, upstream deletions encompassing the 35S enhancer showed that the sequence between -207 and -56 from the cap site comprised nonessential elements, although complete removal of this fragment caused loss of infectivity even when domain spacing was restored by linker insertion. Two separate enhancer domains (-207 to - 150 and -95 to -56) were identified, of which either one or the other, but not both, was required for infectivity. Some mutations affected the cellular levels of viral RNAs in unexpected ways, as with removal of the as-1 enhancer element causing an increase in 35S RNA. Others altered the relative abundance of nuclear and cytoplasmic viral DNAs. Mutations in promoter domains thought to be involved in regulating tissue-specific expression did not significantly affect virus accumulation in leaves versus roots, whereas gene VI mutants showed reduced root accumulation. We conclude that elements associated with the cauliflower mosaic virus 35S promoter contain extensive nonessential regions that can behave differently in their proper context than as isolated elements.

Base Sequence↗