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1.
Arabinogalactan-proteins (AGPs) are abundant plant proteoglycans that react with (β-d-Glc)3 but not (β-d-Man)3 Yariv reagent. We report here that treatment with (β-d-Glc)3 Yariv reagent caused inhibition of root growth of Arabidopsis thaliana (L.) Heynh. seedlings. Moreover, the treated roots exhibited numerous bulging epidermal cells. Treatment with (β-d-Man)3 Yariv reagent did not have any such effects. These results indicate a role for AGPs in root growth and control of epidermal
cell expansion. Because treatment with (β-d-Glc)3 Yariv reagent phenocopies the reb1 (root epidermal cell bulging) mutant of Arabidopsis, AGPs were extracted from the reb1-1 mutant and compared with those of the wild type. The reb1-1 roots contained an approximately 30% lower level of AGPs than the wild type. More importantly, while the profile of AGPs
from wild-type roots showed two major peaks upon crossed electrophoresis, the profile of AGPs from reb1-1 roots exhibited only one of the major peaks. Therefore, the reb1 phenotype appears to be a result of defective or missing root AGPs. Taken together, this pharmacological and genetic evidence
strongly indicates a function of AGPs in the control of root epidermal cell expansion.
Received: 13 February 1997 / Accepted: 1 April 1997 相似文献
2.
Arabinogalactan-proteins (AGPs) are proteoglycans with a high level of galactose and arabinose. Their current functions in
plant development remain speculative. In this study, (β-D-glucosyl)3 Yariv phenylglycoside [(β-D-Glc)3] was used to perturb AGPs at the plasmalemma-cell wall interface in order to understand their functional significance in
cell wall assembly during pollen tube growth. Lily (Lilium longiflorum Thunb.) pollen tubes, in which AGPs are deposited at the tip, were used as a model. Yariv phenylglycoside destabilizes the
normal intercalation of new cell wall subunits, while exocytosis of the secretory vesicles still occurs. The accumulated components
at the tip are segregated between fibrillar areas of homogalacturonans and translucent domains containing callose and AGPs.
We propose that the formation of AGP/(β-D-Glc)3 complexes is responsible for the lack of proper cell wall assembly. Pectin accumulation and callose synthesis at the tip
may also change the molecular architecture of the cell wall and explain the lack of proper cell wall assembly. The data confirm
the importance of AGPs in pollen tube growth and emphasize their role in the deposition of cell wall subunits within the previously
synthesized cell wall.
Received: 14 August 1997 / Accepted: 9 September 1997 相似文献
3.
Juliana Bello Baron Maurer Adaucto Bellarmino Pereira-Netto Filomena Angela Pettolino Yolanda Maria Gaspar Antony Bacic 《Trees - Structure and Function》2010,24(2):391-398
Arabinogalactan-proteins (AGPs) are a family of highly glycosylated hydroxyproline-rich glycoproteins implicated in several
aspects of plant growth and development. (β-d-glucosyl)3 Yariv phenylglycoside (β-GlcY), commonly known as Yariv reagent, selectively binds AGPs. We treated cell suspension cultures
of Araucaria
angustifolia, the Brazilian pine, with β-GlcY and observed inhibition of biomass increase in a culture medium with 50 μM β-GlcY. However,
the growth was not inhibited by (α-d-galactosyl)3 Yariv phenylglycoside (α-GalY) which does not bind AGPs. Fluorescein diacetate staining of cells indicated that β-GlcY severely
affected cell viability. However, cell swelling, bursting and release of cellular contents, all characteristics of necrotic
cell death, were not observed in β-GlcY-treated cells. Instead, programmed cell death (PCD) structural changes such as cytoplasmic
shrinkage and condensation were observed in β-GlcY-treated cells. In addition, callose accumulation, which is another marker
of PCD, was also observed in β-GlcY-treated cells. The use of both, Ac-VEID-CHO, an inhibitor of caspase-like proteolytic
activity related to PCD, and phenyl methyl sulphonyl fluoride (PMSF), a protease inhibitor known to suppress PCD, in the culture
medium did not reverse the growth inhibition caused by β-GlcY. These data indicate that the β-GlcY-induced inhibition of Araucaria cell’s growth is related to AGP perturbation, and also that this growth inhibition is due to increased cell death not driven
by necrosis. 相似文献
4.
Summary. Arabinogalactan proteins (AGPs) are a class of highly glycosylated proteins widely distributed in higher plants and thought
to be involved in plant growth and development. In the present paper, Western blotting with the monoclonal antibodies JIM4,
JIM13, and LM2 showed that JIM13 reacted best with total protein extracts from flowers and siliques of Arabidopsis thaliana. This monoclonal antibody was therefore used as a probe to localize the AGP epitope in zygotic embryos at different developmental
stages. Immunofluorescent labeling with JIM13 showed that AGPs were mainly distributed in the embryo proper and the top 1
to 2 cells and basal part of suspensors. The results of immunogold labeling confirmed the JIM13 epitope distribution in the
different cells of the suspensor. AGP immunofluorescence was also observed at the shoot apex meristem during transition from
the globular to the heart embryo stage, but this gradually disappeared after the torpedo stage. After (β-D-Glc)3 Yariv phenylglycoside (βGlcY), a synthetic reagent that specifically binds to AGPs, was added to A. thaliana ovule culture medium, the survival rate and frequency of development of ovules at the zygote stage decreased in a concentration-dependent
manner, with complete inhibition at 100 μM. The frequency of embryo differentiation from the globular stage to heart or later
stages also decreased sharply. When βGlcY was removed 24 h after inoculation, the inhibitory effects were reversible in a
concentration-dependent and time-dependent manner. The results show that βGlcY can inhibit embryo development and differentiation
in A. thaliana, and the inhibitory effects are concentration dependent and reversible, indicating that AGPs are involved in embryo differentiation
and shoot meristem formation. The possible roles of AGPs in A. thaliana zygotic embryo development are also discussed.
Correspondence and reprints: Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life
Sciences, Wuhan University, Wuhan 430072, People’s Republic of China. 相似文献
5.
Jacqueline Capataz-Tafur Gabriela Trejo-Tapia Mario Rodríguez-Monroy Gabriela Sepúlveda-Jiménez 《Plant Cell, Tissue and Organ Culture》2011,106(1):169-177
Arabinogalactan proteins (AGPs) are glycoproteins present at cell surfaces. Although exact functions of AGPs remain elusive,
they are implicated in plant growth and development. The aim of this study was to evaluate the role of AGPs in the process
of cell aggregation of Beta vulgaris L. suspension cultures. It was observed that B. vulgaris suspension cultures accumulated AGPs in parallel form to its cell growth. The AGPs maximum content in the stationary phase
was 0.330 mg g−1 dry weight (DW) in the cell wall (CW) and 1.534 mg g−1 DW in the culture medium (CM), generating cell aggregates >500 μm (93.21% DW). The addition of tunicamycin (TM) caused a
reduction of AGPs content in CW and CM of 46 and 64%, respectively. These changes were associated with inhibition of growth
and the reduction of the cell aggregates >500 μm (50.0% DW). When TM was removed from the CM, cell growth, aggregation, and
AGPs content on CW and CM were recovered. Precipitation of AGPs with Yariv reagent generated a reduction of 61.14% of AGPs
content in CW and a total inhibition of AGPs secretion in CM. This Yariv treatment generated a reduction in the cell aggregates
>500 μm of 51.31% of DW. When the Yariv reagent was removed from the culture, cells did not recover their AGPs accumulation.
In addition, cell cultures did not recover their ability to grow and aggregate. These results indicate that AGPs are molecules
required in the cellular aggregation process of B. vulgaris L. suspension cultures. 相似文献
6.
Direct somatic embryogenesis was induced in root tissues of the Cichorium hybrid `474' (C. intybus L. var. sativum×C. endivia L. var. latifolia). Addition of β-d-glucosyl Yariv reagent (βGlcY), a synthetic phenylglycoside that specifically binds arabinogalactan-proteins (AGPs), to the
culture medium blocked somatic embryogenesis in a concentration-dependent manner with complete inhibition of induction occurring
at 250 μM βGlcY. The AGP-unreactive α-d-galactosyl Yariv reagent had no biological activity in this system. Upon transfer of 250 μM βGlcY-treated roots to control
conditions, somatic embryogenesis was recovered with a time course similar to that of control roots. The βGlcY penetrated
roots and bound abundantly to developing somatic embryos, to the root epidermis and the stele. Immunofluorescence and immunogold
labelling using monoclonal antibodies (JIM13, JIM16 and LM2) revealed that AGPs were localised in the outer cell walls peripheral
cells of the globular embryo. A spatio-temporal expression of AGPs appeared to be associated with differentiation events in
the somatic embryo during the transition from the globular stage to the torpedo stage. To verify βGlcY specificity, molecules
that bound βGlcY were extracted from treated conditioned medium and identified as AGPs by using the same monoclonal antibodies.
In addition, AGPs were found to be abundantly present in the medium during embryogenic culture. All of these results establish
the implication of AGPs in embryo development, and their putative role in somatic embryogenesis is discussed.
Received: 26 August 1999 / Accepted: 28 January 2000 相似文献
7.
Arabinogalactan proteins (AGPs) have been implicated in plant development including sexual plant reproduction. In this paper,
the expression of AGPs and the effects of β-glucosyl Yariv reagent (βGlcY, which binds arabinogalactan proteins) in embryo
development and cotyledon formation were investigated. Immunofluorescence assay displayed that the expression of AGPs labeled
with antibody JIM13 was developmentally regulated. In early stages, AGPs were evenly distributed in the whole embryo, except
for a short polar expression in the basal suspensor cell. In the globular stage of embryo, AGPs were condensed in the embryo
proper (EP), apex of the EP, and at the juncture of the EP and suspensor. In heart-shaped embryo, APGs were only present at
the juncture of the EP and suspensor. Immunogold labeling assay showed that the strong expression of AGPs at the juncture
of the EP and suspensor was localized in the cell wall. Provision of βGlcY to the in vitro ovule culture medium caused delayed
growth of embryos, cotyledon defect and abnormal venation pattern. Consequently, βGlcY induced the death of defective seedlings
with the characteristics of deformed or irregular single cotyledon. Our results suggested that AGPs play functional roles
in embryo development, cotyledon formation and seedling morphology establishment in Nicotiana tabacum L. 相似文献
8.
In lily, adhesion of the pollen tube to the transmitting-tract epidermal cells (TTEs) is purported to facilitate the effective movement of the tube cell to the ovary. In this study, we examine the components of the extracellular matrices (ECMs) of the lily pollen tubes and TTEs that may be involved in this adhesion event. Several monoclonal antibodies to plant cell wall components such as esterified pectins, unesterified pectins, and arabinogalactan-proteins (AGPs) were used to localize these molecules in the lily pollen tube and style at both light microscope (LM) and transmission electron microscope (TEM) levels. In addition, (-d-Glc)3 Yariv reagent which binds to AGPs was used to detect AGPs in the pollen tube and style. At the LM level, unesterified pectins were localized to the entire wall in in-vivo- and in-vitro-grown pollen tubes as well as to the surface of the stylar TTEs. Esterified pectins occurred at the tube tip region (with some differences in extent in in-vivo versus in-vitro tubes) and were evenly distributed in the entire style. At the TEM level, esterified pectins were detected inside pollen tube cell vesicles and unesterified pectins were localized to the pollen tube wall. The in-vivo pollen tubes adhere to each other and can be separated by pectinase treatment. At the LM level, AGP localization occurred in the tube tip of both in-vivo- and in-vitro-grown pollen tubes and, in the case of one AGP probe, on the surface of the TTEs. Another AGP probe localized to every cell of the style except the surface of the TTE. At the TEM level, AGPs were mainly found on the plasma membrane and vesicle membranes of in-vivo-grown pollen tubes as well as on the TTE surface, with some localization to the adhesion zone between pollen tubes and style. (-d-Glc)3 Yariv reagent bound to the in-vitro-grown pollen tube tip and significantly reduced the growth of both in-vitro- and in-vivo-grown pollen tubes. This led to abnormal expansion of the tube tip and random deposition of callose. These effects could be overcome by removal of (-d-Glc)3 Yariv reagent which resulted in new tube tip growth zones emerging from the flanks of the arrested tube tip. The possible roles of pectins and AGPs in adhesion during pollination and pollen tube growth are discussed.Abbreviations AGP
arabinogalactan-protein
- ECM
extracellular matrix
- Glc
glucose
- MAbs
monoclonal antibodies
- LM
light microscope
- Man
mannose
- TEM
transmission electron microscope
- TTE
transmitting tract epidermal cell
The authors thank Michael Georgiady for assistance with the preparation of material for the TEM immunolocalization, Diana Dang for her help with the pectinase experiment, and Kathleen Eckard for assistance in all aspects of this study. The MAbs were the generous gifts of Dr. J.P. Knox. G.Y. Jauh thanks Dr. E.A. Nothnagel for assistance in making the Yariv reagent and for the gift of the control (-d-Man)3 Yariv reagent. This work is in partial fulfilment of the dissertation requirements for a PhD degree in Botany and Plant Sciences for G.Y. Jauh at the University of California, Riverside. This work was supported by National Science Foundation grant 91-18554 and an R.E.U. grant to E.M.L. 相似文献
9.
Arabinogalactan proteins (AGPs) are abundant plant cell surface proteoglycans widely distributed in plant species. Since high
concentrations of β-glucosyl Yariv reagent (βglcY), which binds selectively to AGPs, inhibited cell division of protoplast-regenerated
cells of the liverwort Marchantia polymorpha L. (Shibaya and Sugawara in Physiol Plant 130:271–279, 2007), we investigated the mechanism underlying the inability of the cells to divide normally by staining nuclei, cell walls and
β-1,3-glucan. Microscopic observation showed that the diameter of regenerated cells cultured with βglcY was about 2.8-fold
larger than that of cells cultured without βglcY. The cells cultured with βglcY were remarkably multinucleated. These results
indicated that βglcY did not inhibit mitosis but induced multinucleation. In the regenerated cells cultured with low concentrations
of βglcY (5 and 1 μg ml−1), the cell plate was stained strongly by βglcY, suggesting abundant AGPs in the forming cell plate. In these cell plates,
β-1,3-glucan was barely detectable or not detected. In multinucleated cells, cell plate-like fragments, which could not reach
the cell wall, were frequently observed and they were also stained strongly by βglcY. Our results indicated that AGPs might
have an important role in cell plate formation, and perturbation of AGPs with βglcY might result in remarkable multinucleation
in protoplast-regenerated cells of M. polymorpha.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
Arabinogalactan proteins (AGPs) are a class of highly glycosylated, widely distributed proteins in higher plants. In the previous
study, we found that the green fluorescence from JIM13-labeled AGPs was mainly distributed in embryo proper and the basal
part of suspensor but gradually disappeared after the torpedo-stage embryos in Arabidopsis. And (β-d-Glc)3 Yariv phenylglycoside (βGlcY), a synthetic reagent that specifically binds to AGPs, could inhibit embryo development. In
this study, as a continuous work, we investigated the AGP functions in embryo germination, cotyledon formation, and cell wall
deposition in Arabidopsis embryos by using immunofluorescent, immunoenzyme, transmission electron microscopy (TEM), and Fourier transform infrared
spectroscopy (FTIR) techniques. The results showed that 50 μM βGlcY caused inhibition of embryo germination, formation of
abnormal cotyledon embryos, and disorder of cotyledon vasculature. Compared with the normal embryos in vitro and in vivo,
the AGPs and pectin signals were quite weaker in the whole abnormal embryos, whereas the cellulose signal was stronger in
the shoot apical meristem (SAM) of abnormal embryo by calcofluor white staining. The FTIR assay demonstrated that the cell
wall of abnormal embryos was relatively poorer in pectins and richer in cellulose than those of normal embryos. By TEM observation,
the SAM cells of the abnormal embryos had less cytoplasm, more plastid and starch grains, and larger vacuole than that of
normal embryos. These results indicated that AGPs may play roles in embryo germination, cotyledon formation, cell wall cellulose
and pectin deposition, and cell division potentiality during embryo development of Arabidopsis. 相似文献
11.
Cultured cells of tobacco (Nicotiana tabacum L.) adapted to 428 mM NaCl exhibited a reduced rate of cell enlargement, which is probably due to decreased cell-wall extensibility. Arabinogalactan-protein (AGP) has been implicated as a cell-wall-loosening factor (Schopfer 1990). Levels of plasma membrane and extracellular AGPs that react with Yariv reagent were measured and compared between NaCl-adapted and unadapted tobacco cells. Unadapted cells contained a very high level of AGPs on the plasma membrane, which amounted to 0.16 g·g–1 membrane protein. In contrast, AGPs were virtually undetectable on the plasma membrane of NaCl-adapted cells. Accumulation of AGPs was also decreased in culture media of NaCl-adapted cells. These data support the hypothesis that AGPs participate in cell expansion. Possible mechanisms of the proposed cell-expansion role of AGPs are discussed.Abbreviations AGP
arabinogalactan-protein
- S0, S25 cells
un-adapted, NaCl-adapted tobacco cells
This work was supported in part by a Mcknight Foundation fellowship to J.K.Z. This is journal paper No. 13,569 of Purdue University Agricultural Experimental Station. The authors thank Dr. Eugene A. Nothnagel for the Yariv reagent gift and for helpful discussion. The authors also thank Glenda McClatchey for excellent technical assistance. 相似文献
12.
A biochemical investigation of arabinogalactan proteins (AGPs) in Physcomitrella
patens was undertaken with particular emphasis on the glycan chains. Following homogenization and differential centrifugation of
moss gametophytes, AGPs were obtained by Yariv phenylglycoside-induced precipitation from the soluble, microsomal membrane,
and cell wall fractions. Crossed-electrophoresis indicated that each of these three AGP fractions was a mixture of several
AGPs. The soluble AGP fraction was selected for further separation by anion-exchange and gel-permeation chromatography. The
latter indicated molecular masses of ∼100 and 224 kDa for the two major soluble AGP subfractions. The AGPs in both of these
subfractions contained the abundant (1,3,6)-linked galactopyranosyl residues, terminal arabinofuranosyl residues, and (1,4)-linked
glucuronopyranosyl residues that are typical of many angiosperm AGPs. Unexpectedly, however, the moss AGP glycan chains contained
about 15 mol% terminal 3-O-methyl-l-rhamnosyl residues, which have not been found in angiosperm AGPs. This unusual and relatively nonpolar sugar, also called
l-acofriose, is likely to have considerable effects on the overall polarity of Physcomitrella AGPs. A review of the literature indicates that the capacity to synthesize polymers containing 3-O-methyl-l-rhamnosyl residues is present in a variety of bacteria, algae and lower land plants but became less common through evolution
to the extent that this sugar has been found in only a few species of angiosperms where it occurs as a single residue on steroidal
glycosides. 相似文献
13.
Summary. Western blot analysis indicated the presence of two epitopes recognized by the anti-arabinogalactan protein antibodies JIM13
and LM2 and the absence of the JIM4 epitope in mature tobacco anthers. Immunoenzyme localization of arabinogalactan proteins
(AGPs) with JIM13 showed that AGPs accumulate mainly at the early stages of anther development. AGP content and distribution
were also investigated at the ultrastructural level in pollen tubes grown in vivo and in vitro. Abundant AGPs were present
in the transmitting tissue of styles, and the AGP content of the extracellular matrix changed during pollen tube growth. In
pollen tubes, immunogold particles were mainly distributed in the cell wall and cytoplasm, especially around the peripheral
region of the generative-cell wall. β-D-Glucosyl Yariv reagent, which specifically binds to AGPs, caused slow growth of pollen
tubes and reduced immunogold labeling of AGPs with JIM13 in vitro. These data suggest that AGPs participate in male gametogenesis
and pollen tube growth and may be important surface molecules in generative and sperm cells.
Correspondence and reprints: Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life
Sciences, Wuhan University, Wuhan 430072, People’s Republic of China. 相似文献
14.
Elena Antoshina Lawrence E. Ostrowski 《In vitro cellular & developmental biology. Animal》1997,33(3):212-217
Summary We are studying the regulation of ciliated cell differentiation using an in vitro model of tracheal regeneration. Previously, we reported that removal of growth stimulating compounds such as epidermal growth
factor (EGF) and cholera toxin reduced DNA synthesis and cell number while increasing ciliated cell differentiation (Clark
et al., 1995). This result suggested that the induction of growth arrest may stimulate terminal differentiation of airway
epithelial cells into ciliated cells. Transforming growth factor βs (TGFβs) inhibit epithelial cell proliferation and have
also been shown to stimulate epithelial cell differentiation. In this study, the effect of TGFβ1 on growth and ciliated cell differentiation of rat tracheal epithelial (RTE) cells was examined. TGFβ1 inhibited [3H]thymidine incorporation by RTE cells in a dose-dependent manner. A 40% inhibition was observed after a 24-h incubation with
10 pM TGFβ1. Continuous treatment with TGFβ1 (1–50 pM) also reduced cell number during the time when ciliogenesis occurs. This reduction resulted in part from a loss of cells
through exfoliation, in addition to the inhibition of proliferation. The exfoliated cells exhibited several morphological
features characteristic of apoptosis, including shrunken cells, condensed and fragmented nuclei, and intact organelles. In
addition, electrophoretic analysis of genomic DNA analysis isolated from exfoliated cells demonstrated the presence of a nucleosomal
ladder. However, in contrast to the removal of EGF, treatment with TGFβ1 for 7 d did not increase ciliated cell differentiation. TGFβ1 is, therefore, capable of inhibiting proliferation and increasing
apoptosis in RTE cells without stimulating ciliated cell differentiation. 相似文献
15.
The cell wall loosening enzymes viz. glycosidases, polygalacturonase and xylanase were analyzed in cytoplasmic and wall bound fractions extracted from control
and hormone (GA3 NAA, PAA) treated internodes, as they are known to play a key role in cell wall metabolism. Among the glycosidases, wall
bound β-glucosidase and α-galactosidase activities were significantly correlated with age of control internodes. Cytoplasmic
α-galactosidase showed significant correlation in hormone treated internodes. Maximum correlation was observed in GA3, followed by PAA and NAA. Wall bound xylanase activity was well correlated with length only in NAA treated internodes and
less after GA3 treatment while cytoplasmic xylanase showed correlation with intrnode length only in control and after NAA treatment. Cytoplasmic
polygalacturonase showed correlation with internode length only after GA3 treatment while wall bound polygalacturonase showed correlation with internode length after NAA treatment. The possible role
of these enzymes in internode development is discussed. 相似文献
16.
Margaret Smallwood Edwin A. Yates William G. T. Willats Helen Martin J. Paul Knox 《Planta》1996,198(3):452-459
Arabinogalactan-proteins (AGPs) occurring in suspension-cultured rice (Oryza saliva L.) cells, their conditioned medium and at the rice root apex were investigated using monoclonal antibodies and the AGP-binding -glucosyl Yariv reagent ( GlcY). A monoclonal antibody, LM2, was generated that recognized an acidic carbohydrate epitope common to two soluble AGPs occurring in the conditioned medium of proliferating rice cells, membrane-associated AGPs (rmAGP) in the cultured cells and two AGPs at the rice root apex. In addition, LM2 recognized AGPs secreted by suspensioncultured carrot (Daucus carota L.) cells. The two AGPs of the rice culture medium, srAGP1 and srAGP2, were discriminated by their mobilities during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, reaction with GlcY, the presence of arabinogalactan epitopes and anion-exchange chromatography. The association of rmAGP with the plasma membrane was investigated by Triton-X-114/aqueous partitioning of both microsomal and plasma-membrane preparations and rmAGP was found to partition into the detergent phase, indicating that AGPs are hydrophobic plasma-membrane proteins in rice. This was in contrast to plasma-membrane AGPs of suspension-cultured carrot cells that partitioned into the aqueous phase. At the rice root apex most of the AGP was associated with the microsomal fraction and also partitioned into the detergent phase, although a distinct highmolecular-mass AGP entered the aqueous phase.Abbreviations AGP
arabinogalactan-protein
- GlcY
-glucosyl Yariv reagent
- ELISA
enzyme-linked immunosorbent assay
We gratefully acknowledge support from the Leverhulme Trust, the UK Biotechnology and Biological Sciences Research Council and the Royal Society. 相似文献
17.
Uncoupling secretion and tip growth in lily pollen tubes: evidence for the role of calcium in exocytosis 总被引:7,自引:0,他引:7
Stéphane J. Roy Terena L. Holdaway-Clarke Grant R. Hackett Joseph G. Kunkel Elizabeth M. Lord Peter K. Hepler 《The Plant journal : for cell and molecular biology》1999,19(4):379-386
Cytoplasmic calcium concentration ([Ca2+]i) and extracellular calcium (Ca2+o) influx has been studied in pollen tubes of Lilium longliflorum in which the processes of cell elongation and exocytosis have been uncoupled by use of Yariv phenylglycoside ((β-D-Glc)3). Growing pollen tubes were pressure injected with the ratio dye fura-2 dextran and imaged after application of (β-D-Glc)3, which binds arabinogalactan proteins (AGPs). Application of (β-D-Glc)3 inhibited growth but not secretion. Ratiometric imaging of [Ca2+]i revealed an initial spread in the locus of the apical [Ca2+]i gradient and substantial elevations in basal [Ca2+]i followed by the establishment of new regions of elevated [Ca2+]i on the flanks of the tip region. Areas of elevated [Ca2+]i corresponded to sites of pronounced exocytosis, as evidenced by the formation of wall ingrowths adjacent to the plasma membrane. Ca2+o influx at the tip of (β-D-Glc)3-treated pollen tubes was not significantly different to that of control tubes. Taken together these data indicate that regions of elevated [Ca2+]i, probably resulting from Ca2+o influx across the plasma membrane, stimulate exocytosis in pollen tubes independent of cell elongation. 相似文献
18.
Dose-related influence of sodium selenite on apoptosis in human thyroid follicles in vitro induced by iodine, EGF, TGF-β, and H2O2 总被引:1,自引:0,他引:1
Lehmann P Rank P Hallfeldt KL Krebs B Gärtner R 《Biological trace element research》2006,112(2):119-130
Apoptosis of thyroid follicular cells is induced by high doses of iodide, epidermal growth factor (EGF), transforming growth
factor-β (TGF-β), as well as H2O2 and might be attenuated by antioxidants. Therefore, we examined the apoptotic index induced by these substances in selenium-treated
vs untreated human thyroid follicular cells. Reconstituted human thyroid follicles were incubated with sodium selenite (10
or 100 nM) for 72 h; controls received none. The follicles were then distributed to 24-well plates and incubated with potassium iodide
(5, 10, or 20 nM), EGF (5 ng/mL), TGF-β (5 ng/mL), or H2O2 (100 μM). Apoptosis was determined by a mitochondrial potential assay and the number of apoptotic cells counted by two independent,
experienced technicians and the glutathione peroxidase (GPx) activity was determined. A significant increase of apoptic cells
was obtained in control thyroid follicles treated with iodine (5, 10, or 20 μM), thyroid-stimulating hormone (TSH) 1, or 10 mU/mL in combination with 5 and 10 μM iodine, EGF (5 ng/mL) and TGF-β (5 ng/mL), or H2O2 (100 μM) (p<0.001). In contrast, in thyroid follicles preincubated with 10 or 100 nM sodium selenite, the apoptototic index was identical to the basal rate. In H2O2-treated follicles, the apoptotic index was still significantly elevated but 50% lower compared to control cells. The GPx
activity increased from 1.4±0.2 to 2.25±0.4 mU/μg DNA with 10 nM selenite and 2.6+0.4 mU/μg DNA with 100 nM selenite. Sodium selenite might increase the antioxidative potential in human thyroid follicles in vitro and therefore diminish
the apoptosis induced by TGF-β, EGF, iodide, and even H2O2 相似文献
19.
Developmental expression and perturbation of arabinogalactan-proteins during seed germination and seedling growth in tomato 总被引:4,自引:0,他引:4
Arabinogalactan-proteins (AGPs) are a family of highly glycosylated hydroxyproline-rich glycoproteins present throughout the plant kingdom. A synthetic chemical reagent, ( β - d -Gal)3 Yariv reagent, specifically binds AGPs and can be used for histochemical staining, isolating and probing the function of AGPs. Here, the role of AGPs in tomato ( Lycopersicon esculentum Mill. cv. UC82B) seed germination and seedling growth was examined by following expression of AGPs during these events and by treatment with ( β - d -Gal)3 Yariv to perturb AGP function. AGP expression changed during germination and seedling development both quantitatively and qualitatively as revealed by analysis of total AGP content, crossed electrophoresis patterns, RNA blots using LeAGP-1 probe, and western blots with LeAGP-1, JIM13, and MAC207 antibodies. ( β - d -Gal)3 Yariv treatment of seeds and developing seedlings did not affect percent seed germination, but markedly inhibited seedling growth in roots and to a lesser degree in shoots. Root growth inhibition encompassed reductions in overall root length, epidermal root cell elongation, root cell numbers and root hair formation. This growth inhibition was reversible following removal of ( β - d -Gal)3 Yariv. In a related experiment, water uptake by tomato seedlings was greatly inhibited by ( β - d -Gal)3 Yariv treatment. Based on these experiments, AGPs are clearly associated with tomato seedling development and likely to function in root growth, more specifically in cell elongation, cell proliferation, root hair formation and water uptake. 相似文献
20.
Barley endosperm begins development as a syncytium where numerous nuclei line the perimeter of a large vacuolated central cell. Between 3 and 6 days after pollination (DAP) the multinucleate syncytium is cellularized by the centripetal synthesis of cell walls at the interfaces of nuclear cytoplasmic domains between individual nuclei. Here we report the temporal and spatial appearance of key polysaccharides in the cell walls of early developing endosperm of barley, prior to aleurone differentiation. Flowering spikes of barley plants grown under controlled glasshouse conditions were hand-pollinated and the developing grains collected from 3 to 8 DAP. Barley endosperm development was followed at the light and electron microscope levels with monoclonal antibodies specific for (1→3)-β-d-glucan (callose), (1→3,1→4)-β-d-glucan, hetero-(1→4)-β-d-mannans, arabino-(1→4)-β-d-xylans, arabinogalactan-proteins (AGPs) and with the enzyme, cellobiohydrolase II, to detect (1→4)-β-d-glucan (cellulose). Callose and cellulose were present in the first formed cell walls between 3 and 4 DAP. However, the presence of callose in the endosperm walls was transient and at 6 DAP was only detected in collars surrounding plasmodesmata. (1→3,1→4)-β-d-Glucan was not deposited in the developing cell walls until approximately 5 DAP and hetero-(1→4)-β-d-mannans followed at 6 DAP. Deposition of AGPs and arabinoxylan in the wall began at 7 and 8 DAP, respectively. For arabinoxylans, there is a possibility that they are deposited earlier in a highly substituted form that is inaccessible to the antibody. Arabinoxylan and heteromannan were also detected in Golgi and associated vesicles in the cytoplasm. In contrast, (1→3,1→4)-β-d-glucan was not detected in the cytoplasm in endosperm cells; similar results were obtained for coleoptile and suspension cultured cells. 相似文献