Journal of Experimental Botany, Vol. 51, No. 344, pp. 521-528,
March 2000
© 2000 Oxford University Press
Immunolocalization of actin in root statocytes of Lens culinaris L.
1 Université Pierre et Marie Curie, Laboratoire CEMV, case courrier 150, Bât. N2, 4 place Jussieu, F-75252 Paris Cedex 05, France
2 Hôpital Saint-Louis, Laboratoire d'Analyse d'Images en pathologie cellulaire, 1 avenue Claude Vellefaux, F-75475 Paris Cedex 10, France
3 Universiteit Antwerpen, Department of Biology, Universiteitsplein 1, B-2610 Wilrijk, Belgium
Received 2 July 1999; Accepted 25 October 1999
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Abstract |
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Lentil root statocytes show a strict structural polarity of their organelles with respect to the g vector. These cells are involved in the perception of gravity and are responsible for the orientation of the root. Actin filaments take part in the positioning of their organelles and could also be involved in the transduction of the gravitropic signal. A pre-embedding immunogold silver technique was carried out with a monoclonal antibody in order to study the distribution of actin cytoskeleton in the statocytes at the electron microscopic level. Some areas were never labelled (cell wall, vacuole, nucleoplasm, mitochondria, starch grains of the amyloplasts) or very slightly labelled (stroma of the amyloplasts). The labelling was scattered in the cytoplasm always close to, or on the nuclear and amyloplast envelopes and the tonoplast. Associations of 2 to 6 dots in file were observed, but these short files were not oriented in one preferential direction. They corresponded to a maximum distance of 0.9 µm. This work demonstrated that each statocyte organelle was enmeshed in an actin web of short filaments arranged in different ways. The images obtained by rhodamine-phalloidin staining were in accordance with those of immunogold labelling. The diffuse fluorescence of the cytoplasm could be explained by the fact that the meshes of the web should be narrow. The vicinity of actin and of the amyloplasts envelope could account for the movement of these organelles that was observed in spatial microgravity.
Key words: Actin, cytoskeleton, immunolocalization, lentil root, pre-embedding technique, statocyte.
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Introduction |
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Root statocytes, located in the centre of the cap, are responsible for gravisensing (Perbal, 1978
; Audus, 1979; Volkmann and Sievers, 1979). These cells show a strict structural polarity of their organelles with respect to the g vector (Sievers and Volkmann, 1972; Perbal, 1978; Hensel and Sievers, 1980; Olsen et al., 1984; Sack and Kiss, 1989; Perbal and Driss-Ecole, 1993): the nucleus is positioned near the wall closest to the meristem (proximal wall), whereas tubules of endoplasmic reticulum (ER) are located near the distal wall. Experiments using cytochalasin B (Hensel, 1985), which inhibits actin filament elongation (Brenner and Korn, 1979; Flanagan and Lin, 1980; Brown and Spudich, 1981), have shown that these organelles are maintained in their respective position by actin filaments. The linkage of the cytoskeleton with the amyloplasts (or statoliths) is more difficult to demonstrate since they sediment under the influence of gravity.
In addition to their role in the positioning of the statocyte organelles, actin filaments could play a role in the transduction mechanism of the gravitropic signal (Sievers et al., 1989, 1991). Another interesting feature was observed in statocytes of roots grown in microgravity, in space: a displacement of the amyloplasts occurred in microgravity (Lorenzi and Perbal, 1990; Volkmann et al., 1991). The kinetics of this movement was studied in lentil root statocytes grown on a 1 g centrifuge and placed during various periods in microgravity (Driss-Ecole et al., 2000). This movement could be due to actin filaments and motor proteins.
Evidence for the presence of actin in many plant cells (Staiger and Schliwa, 1987; Sievers et al., 1989; Tewinkel et al., 1989; Tang et al., 1989; Wada et al., 1998) has been provided using rhodamine-phalloidin staining. Nevertheless, these studies dealt with rhizoids (Chara), protonema (Funaria, Adiantum) or pollen tubes (Nicotiana) where, most of the time, actin microfilaments are organized into bundles. The images concerning actin in root statocytes are less numerous (Hensel, 1989; White and Sack, 1990; Perbal and Driss-Ecole, 1993; Baluska and Hasenstein, 1997) due to the fact that the staining is weak and diffuse.
Other attempts have been made using immunofluorescence (Hensel, 1986; 1989; Koropp and Volkmann, 1994). Koropp and Volkmann used either a new monoclonal antibody (CRA) directed against the actin antigen of cress roots or a commercially available antibody (ICN). The staining was obtained using fluorescein isothiocyanate-conjugated secondary antibody. In both cases, as with rhodamine-phalloidin staining, a diffuse labelling in the statocyte cytoplasm was observed except that the fluorescence intensity with CRA seemed to be stronger than with the ICN antibody.
A new sectioning method suitable for the analysis of microtubules has been developed (Brown et al., 1989) and modified (Vitha et al., 1997) to visualize F-actin arrays (immunofluorescence on low melting point wax sections). However, concerning the actin microfilaments of statocytes (Baluska et al., 1997; Baluska and Hasenstein, 1997), this staining provided almost the same results as those obtained by rhodamine-phalloidin (Perbal and Driss-Ecole, 1993) or by a more conventional immunofluorescence technique (Koropp and Volkmann, 1994).
The authors have chosen to adapt the pre-embedding immunogold silver technique (Holgate et al., 1983; Danscher and Rytter Nörgaard, 1983; Merdes and De Mey, 1990; Vandenbosch, 1991; Burry et al., 1992) to the material in order to visualize actin in the statocytes at the electron microscopic level. This technique permitted the location of G and F actin. Secondary antibody was coupled with 10 nm gold particles. A pretreatment with MBS has also been included (O'Sullivan et al., 1978; Sutoh, 1984) which is effective in reducing the risk of observing artificially bundled actin filaments (Sonobe and Shibaoka, 1989).
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Materials and methods |
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Dry seeds of Lens culinaris L. cv. Verte du Puy were placed on cellulose sponges in culture chambers and hydrated. The growing period was 28 h in darkness at 22 °C.
Immunoblotting
Soluble proteins from root tips (5 mm length) were prepared according to the following procedure. 100 mg of root tips were homogenized in liquid nitrogen with a mortar and a pestle. Subsequently, the powder was suspensed in 9 ml of extraction buffer (0.7 M saccharose, 0.5 M TRIS-HCl pH 7.5, 50 mM EDTA, 0.1 M KCl, 2% ß-mercaptoethanol (v/v), and 2 mM PMSF) for 10 min at 4 °C according to the phenol procedure devised earlier (Schuster and Davies, 1983). The protein pellet was washed three times with 0.1 M ammonium acetate in methanol and once with acetone (100%) and then air dried.
For electrophoresis, soluble proteins were suspended in buffer (Laemmli, 1970) and boiled for 3 min. 20–60 µg of protein were loaded to a 10% SDS-polyacrylamide gel. The low molecular range of proteins from Bio-Rad was used as a standard. Protein content was determinated using the Bio-Rad Laboratory kit. After electrophoresis (2 h at 20 mA), the proteins were transfered to nitrocellulose sheets at 50 V for 3 h at 4 °C using a Transblot cell (Bio-Rad, München, Germany). Then the part of the membrane with standard proteins was stained with Ponceau S (0.2% in 5% acetic acid) and the other part of the membrane subjected to immunostaining. The blots were soaked in blocking solution overnight at 4 °C (TBS, 5% dry milk, 0.02% NaN3), rinsed three times in TBS with 0.05% Tween-20 and then incubated for 3 h at room temperature with a mouse monoclonal antibody (Amersham N.350; anti-chicken gizzard actin; dilution 1 : 1000).The antibody was diluted in TBS, 0.05% Tween-20 and 5% dry milk. After washing three times (in TBS with 0.05% Tween-20) the blots was incubated in the secondary antibody for 1.5 h at room temperature (anti-mouse IgG-alkaline phosphatase Fab fragments; Boehringer No. 1198661; dilution: 2.5 U ml-1). After three 10 min washing periods in TBS-Tween-20 the blot was incubated in a development buffer (TRIS-MgCl2 pH 9.5) and then in a BCIP/NBT colour development solution following the Bio-Rad procedure. Controls omitted the primary antibody. No band was detected.
Pre-embedding immunogold labelling
At the end of the growing period, the seedlings were treated for 10 min with 100 µM MBS (stock solution: 100 mM in DMSO), washed in stabilizing buffer (SB: 50 mM PIPES, 5 mM EGTA, 2 mM MgSO4, pH 6.8) and were fixed in the vertical position for 3 h at 4 °C with 3% paraformaldehyde plus 0.5% glutaraldehyde in SB (according to Sonobe and Shibaoka, 1989). The roots were rinsed in SB and sectioned longitudinally and axially in two parts under a stereomicroscope with a razor blade. The two half-sections of the roots were treated for 5 min by Triton X-100 0.5% in SB, washed in SB and then treated twice with sodium borohydride (1 mg ml-1 in SB; according to Merdes et al., 1991). Then the sections were treated for 30 min in a blocking buffer (BB: 2% BSA, 1% fish gelatin, 1% NGS, 0.1% NaN3, and 0.05% Tween-20) and then in a Tween solution (0.025% in PBS). The sections were incubated overnight at 4 °C with the primary anti-actin antibody (see previous section: N-350 dilution 1=20 in BB, filtered through Whatman filter device, 0.2 µm pore size).
The sections, washed twice in filtered PBS and once in BB, were incubated with the secondary antibody gold (10 nm) conjugated goat anti-mouse IgG Sigma G-7652; dilution 1 : 20 in BB). Following several washing periods with PBS and one with BB the sections were post-fixed with 1.25% glutaraldehyde in PBS for 15 min and rinsed in excess bi-distilled water.
Silver amplification were performed in the dark for 10 min with SEM kit (Amersham). The sections were then washed in excess bi-distilled water and stained en bloc with 0.5% uranyl acetate in the dark for 10 min. Half-sections of the roots were dehydrated in ethanol and embedded in araldite. Ultra-thin sections were made for observation in electron microscopy. Controls were run by omitting the primary antibody from the first incubation: no labelling was detected on the sections.
Rhodamine-phalloidin staining
Seedlings were treated by MBS and washed in SB as described above. Then they were fixed in the vertical position for 3 h at 4 °C by 3% paraformaldehyde in SB and rinsed in SB. The roots were sectioned longitudinally and axially in two parts and the sections were placed for 3 h in the dark at room temperature in 0.22 µM rhodamine-phalloidin (Molecular Probes, Inc). After a brief wash the sections were mounted in Mowiol (Calbiochem) for examination by confocal microscopy (MRC-600, Bio-Rad).
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Results |
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Rhodamine-phalloidin staining
By using confocal microscopy it is possible optically to section the statocytes (Fig. 1A
). The section goes through the amyloplasts and makes it possible to see that the internal part of these organelles is not labelled. A diffuse fluorescence is observed in the cytoplasm located around the amyloplasts. At the proximal part of the statocyte the optical section goes tangentially to the nucleus where a bright and diffuse fluorescence can be detected as well as some short and bright small strands (small group of filaments; Fig. 1A, black arrows).
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The most external cells of the root tip (Fig. 1B) show large vacuoles crossed by thin cytoplasmic trabeculae (Fig. 1B, white arrow) which are labelled by rhodamin-phalloidin demonstrating that actin is present at this level. Some bright small strands can be seen in the cytoplasm (Fig. 1B, black arrows) and around the amyloplasts. It must be noted that typical bundles of microfilaments are not observed in these cells as in Lepidium secretory cells (Baluska et al., 1997
).
Immunoblotting and immunogold-silver staining
The monoclonal anti-actin antibody (Fig. 2) recognizes one polypeptide since only one band located at 43 kDa can be revealed. This 43 kDa polypeptide corresponds to actin.
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Figure 3A–D
shows a whole lentil root statocyte and details of the nucleus, amyloplasts and ER of other statocytes treated by the monoclonal anti actin antibody. The gold–silver particles are spread all over the cytoplasm (Fig. 3A) but the cell walls, the starch grains in the amyloplasts (Fig. 3A, C), the mitochondria (Fig. 3A–D), the nucleoplasm (Fig. 3A, B) do not show any particles. In Fig. 3B (arrow) a longitudinal section of the statocyte shows labelling in a cytoplasmic area surrounded by the nucleoplasm. The density of the cytoplasm decreases substantially upon a short extraction by Triton X-100 (Fig. 3B, C), but gold–silver particles remain located close to or on the nuclear envelope (Fig. 3B) or close to, or on the amyloplast envelope (Fig. 3A, C). A few times, dots are observed in the stroma of the amyloplasts (Fig. 3C). The remaining parts of cytoplasm are associated with labelled particles and sometimes the residues look like filaments on which the dots are lined up (Fig. 3C, arrow). Numerous dots are observed in the distal cytoplasm occupied by the ER (Fig. 3D) and the dots can be linked to the ER tubules (Fig. 3A, ER). Frequently the gold–silver particles are associated by two or three (Fig. 3B, D, arrowheads) or by four to six dots (Fig. 3D, arrow) which correspond to a distance of 0.35–0.9 µm. It must be stressed that these files of dots are not oriented in a preferential direction.
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Figure 4A
and B show cells of the external layer of the root tip identical to the cell observed in confocal microscopy (Fig. 1B). As in the statocytes, the particles are spread over the cytoplasm, and the cell walls, the nucleoplasm (Fig. 4A), the mitochondria and the starch grains in the amyloplasts (Fig. 4B) are not labelled. No dots can be detected in the vacuoles (Fig. 4A, B) but the tonoplast and the transvacuolar trabeculae of cytoplasm are labelled (Fig. 4A, B, arrow) demonstrating that actin is present at this level.
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Discussion |
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Taking account of the involvement of actin in the polarity of lentil root statocytes and of the putative role of this element of the cytoskeleton in the transduction of the gravitropic signal, it was interesting to adapt a method for the vizualization of actin in these cells at the electron microscopic level. As suggested previously (Sonobe and Shibaoka, 1989
) MBS was used prior to fixation in order to prevent the formation of artificially bundled actin filaments and the pre-embedding immunogold silver technique was adjusted to the material. Immunocytochemistry was carried out on root tips prior to their embedment in order to increase antibody access to the antigen in the absence of resin (Vandenbosch, 1991). A good ultrastructural preservation and a maximum retention of antigenicity was insured by the use of a monoaldehyde (paraformaldehyde) in addition to a small amount of glutaraldehyde (Sonobe and Shibaoka, 1989; Merdes and De Mey 1990; Merdes et al., 1991; Vandenbosch, 1991; Koropp and Volkmann, 1994). After a phenol extraction of the proteins of the root, only one band (at 43 kDa) was obtained on the Western blot which demonstrated the specificity of the antibody.
As with the rhodamine-phalloidin staining, the ultra-thin sections of the root cap cells observed after immunoreaction showed that some areas were never labelled: the cell wall, the nucleoplasm, the vacuoles, and the amyloplasts. The two methods permitted the observation that actin surrounded the nucleus as had been demonstrated in isolated cells previously (Seagull et al., 1987). In the statocytes the nucleus was enclosed in a basket of actin and was maintained at the proximal pole at least by these elements of the cytoskeleton.
The immunogold technique had the advantage of detecting labelling at the level of the organelles or in some part of them. Many dots of labelling were located in the region occupied by the ER and sometimes the dots were on the ER tubules. In plants cells (epidermal cells of onion bulb or Droseratentacles, Chara cells, leaf cells of Nicotiana) it has been established that actin was in close association with ER (Quader et al., 1987; Kachar and Reese, 1988; Lichtscheidl et al., 1990; Hepler et al., 1990; Boevink et al., 1998) and that these structural interactions were essential for intracellular movements. In statocytes from cress roots, microfilaments could play a role in the translocation of the ER from the proximal to the distal part of these cells (Hensel, 1989). In lentil root statocytes actin filaments would be necessary to maintain the internal cohesion of the ER complex and these elements of the cytoskeleton could be involved in the movement of the ER tubules from the proximal to the distal part during the differentiation of the statocytes and in the stabilization of the complex near the distal wall in mature statocytes. The interconnection between the ER tubules and the amyloplasts via actin cytoskeleton could account for a role of the ER in gravitropic process.
At the microscopic level the stroma of the amyloplasts sometimes showed some particles, but the amyloplast envelope was always associated with the gold-silver particles. The starch grains were never labelled. No dots were observed in the inner part of the mitochondria, but the labelling was close to the external membrane of this organelle. The dots were also localized on the tonoplast. Such linkage between the periphery of the vacuoles and microfilaments was reported in human epithelial carcinoma cells (Henics and Wheatley, 1997) and could account for the positioning of these organelles or for their movement in Saccharomyces cerevisiae as suggested previously (Hill et al., 1996). The association between actin microfilaments and vacuoles was also reported in pollen tubes of Pyrus communis (Tiwari and Polito, 1988).
The dots of labelling were scattered in the cytoplasm of the statocytes and could be linked to G actin since the molecule could be detected by immunogold–silver staining procedure. Nevertheless, the observation of the images obtained by transmission electron microscopy allowed the detection of associations of 2–6 particles in file corresponding to 0.08–0.9 µm. These short files always had various orientations within the cells and could be associated with actin microfilaments (F actin). This observation could fit with a randomly interconnected network of short units (according to the model proposed by Forgacs, 1995). The bright small strands which were observed with rhodamine-phalloidin should correspond to some of these interconnected fibrous units.
Taking into account that the immunogold particles were located very close to or on the membrane or on the envelope of the statocyte organelles it could be considered that these organelles were connected to the actin network. This linkage allowed the understanding that each organelle movement could be controlled. It was proposed that the disturbance of cytoskeletal microfilaments could generate the transduction step in the gravitropic phenomenon (Sievers et al., 1989, 1991). From an experiment performed in space microgravity, a very short presentation time for the lentil root (26–27 s) was obtained which was consistent with the fact that actin filaments could transduce the gravitropic signal (Perbal and Driss-Ecole, 1994). This conception could be in agreement with the more recent theories about intracellular signalling (Ingber, 1991; Forgacs, 1995; Baluska et al., 1998). In lentil root statocytes, the actin network, in association with motor proteins, could also be responsible for the movement of the amyloplasts observed in roots grown in microgravity (Driss-Ecole et al., 2000).
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Acknowledgments |
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This work was supported by the Centre National des Etudes Spatiales (CNES). TEM observations were performed at the Centre Interuniversitaire de Microscopie Electronique (CIME), Paris.
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Notes |
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4 To whom correspondence should be addressed. Fax: +33 1 44 27 45 82. E-mail:Dominique.Driss{at}snv.jussieu.fr
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Abbreviations |
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BB, Blocking buffer; BCIP/NBT, 5-bromo-4-chloro-3-indolyl phosphatase/nitroblue tetrazolium; BSA, bovine serum albumin; CRA, cress root actin antibody; DMSO, dimethylsulphoxide; EDTA, ethylenediaminetetraacetic acid; EGTA, ethyleneglycol-bis-(ß-aminoethylether)-N,N,N',N'-tetraacetic acid; ICN, anti-chicken gizzard actin IgG, Biomedicals, Meckenheim/Germany; MBS, m-maleimidobenzoyl N-hydroxysuccinimide ester; NaN3, sodium azide; NBT, (p-nitroblue tetrazolium chloride); NGS, normal goat serum; PIPES, piperazine-N,N'-bis(2-ethane-sulphonic acid); PBS, phosphate-buffered saline; PMSF, phenylmethylsulfonyl fluoride; TBS, Tris-buffered saline..
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References |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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Audus LJ.1979. Plant geosensors.Journal of Experimental Botany 30, 1051–1073.
Baluska F, Hasenstein KH.1997. Root cytoskeleton: its role in perception of and response to gravity.Planta 203, S69-S78.[Web of Science][Medline]
Baluska F, Barlow PW, Lichtscheidl IK, Volkmann D.1998. The plant cell body: a cytoskeletal tool for cellular development and morphogenesis.Protoplasma 202, 1–10.
Baluska F, Kreibaum A, Vitha S, Parker JS, Barlow PW, Sievers A.1997. Central root cap cells are depleted of endoplasmic microtubules and actin microfilament bundles: implications for their role as gravity-sensing statocytes.Protoplasma 196, 212–223.[Web of Science][Medline]
Boevink P, Oparka K, Santa Cruz S, Martin B, Betteridge A, Hawes C.1998. Stacks on tracks: the plant golgi apparatus traffics on an actin/ER network.The Plant Journal 15, 441–447.[Web of Science][Medline]
Brenner SL, Korn ED.1979. Substoichiometric concentrations of cytochalasin D inhibit actin polymerization.Journal of Biological Chemistry 254, 9982–9985.
Brown SS, Spudich JA.1981. Mechanism of action of cytochalasin: evidence that it binds to actin filament ends.Journal of Cell Biology 88, 487–491.
Brown RC, Lemmon BE, Mullinax JB.1989. Immunofluorescent staining of microtubules in plant tissues: improved embedding and sectioning techniques using polyethylene glycol (PEG) and Steedman's wax.Botanica Acta 102, 54–61.
Burry RW, Vandré DD, Hayes DM.1992. Silver enhancement of gold antibody probes in pre-embedding electron microscopic immunocytochemistry.Journal of Histochemistry and Cytochemistry 40, 1849–1856.[Abstract]
Danscher G, Rytter Nörgaard JO. 1983. Light microscopic visualization of colloidal gold on resin-embedded tissue.Journal of Histochemistry and Cytochemistry 31, 1394–1398.[Abstract]
Driss-Ecole D, Jeune B, Prouteau M, Julianus P, Perbal G.2000. Lentil root statoliths reach a stable state in microgravity.Planta (in press).
Flanagan MD, Lin S.1980. Cytochalasins block actin filament elongation by binding to high affinity sites associated with F-actin.Journal of Biological Chemistry 255, 835–838.
Forgacs G.1995. On the possible role of cytoskeletal filamentous networks in intracellular signaling: an approach based on percolation.Journal of Cell Science 108, 2131–2143.[Web of Science][Medline]
Henics T, Wheatley DN.1997. Vacuolar cytoplasmic phase separation in cultured mammalian cells involves the microfilament network and reduces motional properties of intracellular water.International Journal of Experimental Pathology 78, 343–354.[Web of Science][Medline]
Hensel W.1985. Cytochalasin B affects the structural polarity of statocytes from cress roots (Lepidium sativum L.).Protoplasma 129, 178–187.[Web of Science][Medline]
Hensel W.1986. Demonstration of microfilaments in statocytes of cress roots.Naturwissenschaften 73, 510–511.[Web of Science][Medline]
Hensel W.1989. Tissue slices living root caps as a model system in which to study cytodifferentiation of polar cells.Planta 177, 296–303.
Hensel W, Sievers A.1980. Effects of prolonged omnilateral gravistimulation on the ultrastructure of statocytes and on the graviresponse of roots.Planta 150, 338–346.[Web of Science][Medline]
Hepler PK, Palevitz BA, Lancelle SA, McCauley MM, Lichtscheidl I.1990. Cortical endoplasmic reticulum in plants.Journal of Cell Science 96, 355–373.
Hill KL, Catlett NL, Weisman LS.1996. Actin and myosin function in directed vacuole movement during cell division in Saccharomyces cerevisiae.Cell Biology 135, 1535–1549.
Holgate CS, Jackson P, Cowen PN, Bird CC.1983. Immunogold-silver staining: new method of immunostaining with enhanced sensitivity.Journal of Histochemistry and Cytochemistry 31, 938–944.[Abstract]
Ingber D.1991. Integrins as mechanochemical transducers.Current Opinion in Cell Biology 3, 841–848.[Medline]
Kachar B, Reese TS.1988. The mechanism of cytoplasmic streaming in characean algal cells: sliding of endoplasmic reticulum along actin filaments.Journal of Cell Biology 106, 1545–1552.
Koropp K, Volkmann D.1994. Monoclonal antibody CRA against a fraction of actin from cress roots recognizes its antigen in different plant species.European Journal of Cell Biology 64, 153–162.[Web of Science][Medline]
Laemmli UK.1970. Cleavage of structural proteins during the assembly of the head of bacteriophage.Nature 227, 680–685.[Medline]
Lichtscheidl IK, Lancelle SA, Hepler PK.1990. Actin-endoplasmic reticulum complexes in Drosera. Their structural relationship with the plasmalemma, nucleus, and organelles in cells prepared by high pressure freezing.Protoplasma 155, 116–126.
Lorenzi G, Perbal G.1990. Root growth and statocyte polarity in lentil seedling roots grown in microgravity or on a slowly rotating clinostat.Physiologia Plantarum 78, 532–537.
Merdes A, De Mey J.1990. The mechanism of kinetochore-spindle attachment and polewards movement analyzed in PtK2 cells at the prophase-prometaphase transition.European Journal of Cell Biology 53, 313–325.[Web of Science][Medline]
Merdes A, Stelzer EHK, De Mey J.1991. The three-dimensional architecture of the mitotic spindle, analyzed by confocal fluorescence and electron microscopy.Journal of Electron Microscopy Technique 18, 61–73.[Web of Science][Medline]
Olsen GM, Mirza JI, Maher EP, Iversen TH.1984. Ultrastructure and movements of cell organelles in the root cap of gravitropic mutants and normal seedlings of Arabidopsis thaliana.Physiologia Plantarum 60, 523–531.[Medline]
O'Sullivan MJ, Gnemmi E, Morris D, Chieregatti G, Simmons M, Simmonds AD, Bridges JW, Marks V.1978. A simple method for the preparation of enzyme-antibody conjugates.Febs Letters 95, 311–313.[Web of Science][Medline]
Perbal G.1978. The mechanism of geoperception in lentil roots.Journal of Experimental Botany 29, 631–638.
Perbal G, Driss-Ecole D.1993. Microgravité et gravitropisme racinaire.Acta Botanica Gallica 140, 615–632.[Web of Science][Medline]
Perbal G, Driss-Ecole D.1994. Sensitivity to gravistimulus of lentil seedling roots grown in space during the IML1 Mission of Spacelab.Physiologia Plantarum 90, 313–318.[Medline]
Quader H, Hofmann A, Schnepf E.1987. Shape and movement of the endoplasmic reticulum in onion bulb epidermis cells: possible involvement of actin.European Journal of Cell Biology 44, 17–26.
Sack FD, Kiss JZ.1989. Root cap structure in wild type and in a starchless mutant of Arabidopsis.American Journal of Botany 76, 454–464.
Schuster AM, Davies E.1983. Ribonucleic acid and protein metabolism in pea epicotyls.Plant Physiology 73, 809–816.
Seagull RW, Falconer MM, Weerdenburg CA.1987. Microfilaments: dynamic arrays in higher plant cells.Journal of Cell Biology 104, 995–1004.
Sievers A, Volkmann D.1972. Verursacht differentieller Druck der Amyloplasten auf ein komplexes Endomembransystem die Geoperzeption in Wurzeln?Planta 102, 160–172.
Sievers A, Kruse S, Kuo-Hang LL, Wendt M.1989. Statoliths and microfilaments in plant cells.Planta 179, 275–278.[Web of Science][Medline]
Sievers A, Buchen B, Volkmann D, Hejnowicz Z.1991. Role of the cytoskeleton in gravity perception. In: Lloyd CW, ed.The cytoskeleton basis of plant growth and form. London: Academic Press, 169–182.
Sonobe S, Shibaoka H.1989. Cortical fine actin filaments in higher plant cells vizualized by rhodamine-phalloidin after pretreatment with m-maleimidobenzoyl N-hydroxysuccinimide ester.Protoplasma 148, 80–86.[Web of Science]
Staiger CJ, Schliwa M.1987. Actin localization and function in higher plants.Protoplasma 141, 1–12.
Sutoh K.1984. Actin-actin and actin-deoxyribonuclease I contact sites in the actin sequence.Biochemistry 23, 1942–1946.[Medline]
Tang X, Lancelle SA, Hepler PK.1989. Fluorescence microscope localization of actin in pollen tubes: comparison of actin antibody and phalloidin staining.Cell Motility and the Cytoskeleton 12, 216–224.[Web of Science][Medline]
Tewinkel M, Kruse S, Quader H, Volkmann D, Sievers A.1989. Visualization of actin filament pattern in plant cells without pre-fixation. A comparison of differently modified phallotoxins.Protoplasma 149, 178–182.
Tiwari SC, Polito VS.1988. Organization of the cytoskeleton in pollen tubes of Pyrus communis: a study employing conventional and freeze-substitution electron microscopy, immunofluorescence, and rhodamine-phalloidin.Protoplasma 147, 100–112.
Vandenbosch KA.1991. Immunogold labelling. In: Hall JL, Hawes C, eds.Electron microscopy of plant cells. Academic Press Limited, 183–218.
Vitha S, Baluska F, Mews M, Volkmann D.1997. Immunofluorescence detection of F-actin on low melting point wax sections from plant tissues.Journal of Histochemistry and Cytochemistry 45, 89–95.
Volkmann D, Sievers A.1979. Graviperception in multicellular organs. In: Haupt W, Feinleib ME, eds.Encyclopedia of plant physiology, Vol. 7. Berlin: Springer-Verlag, 573–600.
Volkmann D, Buchen B, Hejnowicz Z, Tewinkel M, Sievers A.1991. Oriented movement of statoliths studied in a reduced gravitational field during parabolic flights of rockets.Planta 185, 153–161.[Web of Science][Medline]
Wada M, Nozue K, Kadota A.1998. Cytoskeletal pattern changes during branch formation in a centrifuged Adiantum protonema.Journal of Plant Research 111, 53–58.
White RG, Sack FD.1990. Actin microfilaments in presumptive statocytes of root caps and coleoptiles.American Journal of Botany 17, 17–26.
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T. L. Yoder, H.-q. Zheng, P. Todd, and L. A. Staehelin Amyloplast Sedimentation Dynamics in Maize Columella Cells Support a New Model for the Gravity-Sensing Apparatus of Roots Plant Physiology, February 1, 2001; 125(2): 1045 - 1060. [Abstract] [Full Text]
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H. Q. Zheng and L. A. Staehelin Nodal Endoplasmic Reticulum, a Specialized Form of Endoplasmic Reticulum Found in Gravity-Sensing Root Tip Columella Cells Plant Physiology, January 1, 2001; 125(1): 252 - 265. [Abstract] [Full Text]
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