Involvement of an acid phosphatase on cell wall regeneration of tobacco protoplasts

Tobacco protoplasts begin to regenerate their own cell walls, the major components of which are β-glucans, soon after they are transferred into an adequate medium. During the cell wall regeneration the protoplasts secrete two isoforms of acid phosphatase (APase) in time-dependent manner. We determined that one of the isoforms, the Brefeldin A (BFA) sensitive one, is the cell wall resident APase (WP-II) by immunoblotting of the isoform with anti-WP-II antibody. We hypothesized that the WP-II may participate in the deposition of β-glucan microfibrils on the protoplast surface during cell wall regeneration. In order to examine this hypothesis, the protoplasts were cultivated in the cell wall regeneration medium containing the same amount of the BFA-sensitive APase (230 µg protein) as is secreted by the observed number of protoplasts (1.4 × 10⁵ protoplasts) per plate (30-mm-diameter) during a 3-h cultivation after transfer to the cell wall regeneration medium. The addition of WP-II to the cell wall regeneration medium stimulated the deposition of β-glucan microfibrils on the surface of the protoplasts during cell wall regeneration. To determine the stimulative effect of the 60 kDa polypeptide of WP-II, protoplasts were cultivated in the medium containing the amount of anti-WP-II IgG (230 µg protein) equivalent to the BFA-sensitive APase. These results suggested that the 60 kDa polypeptide of WP-II is the BFA-sensitive APase which is responsible for the enhanced deposition of β-glucan microfibrils on the surface of the protoplasts.     

The Effects of Extracellular Calmodulin on Cell Wall Regeneration of Protoplasts and Cell Division

The effects of anti-calmodulin (CaM) serum, CaM antagonist W7-agaroseand exogenous pure CaM on cell wall regeneration of protoplastsand cell division for Angelica dahurica and other plants werestudied. Anti-CaM serum inhibited cell wall regeneration ofprotoplasts and the first cell division in dose-dependent manner,while the same amount of preimmune serum had a much less inhibitoryeffect than anti-CaM serum. The first cell division was alsoinhibited by CaM antagonist W7-agarose. The addition of exogenouspure CaM enhanced cell wall regeneration of protoplasts andthe cell division for several species of plants, while the sameamount of bovine serum albumin had no obvious effect. CaM wasdetected in the normal culture medium by means of enzyme-linkedimmunosorbent assay. Its content increased with the culturetime. The results suggest that extracellular CaM plays an importantrole in promoting cell wall regeneration of protoplasts andcell division. The possible mechanisms by which extracellularCaM achieves its effects are discussed. (Received February 24, 1994; Accepted November 14, 1994)     

植物原生质体的细胞壁再生

细胞壁作为植物细胞重要的组成部分,在决定细胞形状、维持机械支撑、吸收养分等方面发挥重要功能.因此,揭示植物细胞壁合成的调控机制具有重大的生物学意义.基于植物组织水平研究细胞壁的生物合成具有难以控制时间尺度、观察空间狭小等局限性.原生质体作为去除细胞壁的单个细胞是研究细胞壁再生的理想系统.在过去的几十年里报道了大量关于植...     

Regeneration of the cell wall in protoplasts of Candida albicans

To assess the dynamics of synthesis of the wall by regenerating Candida albicans protoplasts deposition of chitin and mannoproteins were investigated ultrastructurally using wheat germ agglutinin conjugated with either horseradish peroxidase or colloidal gold, and Concanavalin A coupled to ferritin respectively.Freshly prepared protoplasts lacked wheat germ agglutinin receptor sites but after 1–2 h of regeneration, they were detected. After 4–5 h of regeneration, the cell wall showed a discrete structure which was only labelled with wheat germ agglutinin in thin sections. At this stage of regeneration the outermost layer of the wall was labelled with clusters of Concanavalin A-ferritin particles.After 8 h regeneration, the cell wall appeared compact, and homogenously marked with wheat germ agglutinin whereas only the surface layers appeared consistently labelled with Concanavalin A-ferritin.From these observations we conclude that C. albicans protoplasts are able to regenerate in liquid medium a cell wall consisting of a network of chitin fibrils and mannoproteins at least (glucan polymers were not determined in the present cytological study). The former are the fundamental component of the inner layers at early stages of regeneration, whereas the latter molecules are predominant in the outer layers of the wall.Abbreviations WGA-HRP wheat germ agglutinin conjugated with horseradish peroxidase - WGA-Au wheat germ agglutinin conjugated with colloidal gold - Con A-ferritin Concanavalin A coupled to ferritin     

Unbiased genomic distribution of genes related to cell morphogenesis in cotton by chromosome mapping

Cell dedifferentiation, somatic embryogenesis, and cell wall regeneration are key steps in plant regeneration. In order to improve the efficiency of plant regeneration in cotton, we mapped genes related to cell morphogenesis. A total of 489 markers, including SSRs, PIPs, and sequence-specific markers related to cell dedifferentiation, somatic embryogenesis, and cell wall regeneration were developed. Only 19 markers showed polymorphism between parents of the mapping population upon high-resolution gel and SSCP analysis, and 21 polymorphic loci were generated. Thirteen loci were mapped on 9 cotton chromosomes, four of which were on Chr16. Seven of the 13 loci were mapped on the At sub-genome and six on the Dt sub-genome. This study provides an overview of the chromosome distribution of genes related to cell morphogenesis in cotton. The markers developed in this study will be useful in marker-assisted selection of better genotypes for plant regeneration in cotton.     

Cell wall enzymatic lysis of the yeast form of Pullularia pullulans and wall regeneration by protoplasts.

During the process of degradation of the cell wall of the yeast form of Pullularia pullulans by the lytic system of micromonospora chalcea samples were withdrawn at different times and observed under phase contrast and electron microscope. The progressive lysis of the walls reveals a fibrillar component inside the apparently amorphous wall. Freeze etched preparations of cells during the formation and regeneration of protoplasts show that the cellular membrane is split and this method allows the smooth external face of the membrane and other internal face covered by particles to be seen. The fact that the smooth face of the membrane is only visible during the preparation or the regeneration of protoplasts and very rarely when intact cells are fractured, suggests a strong adherence between cell wall and this external layer of the membrane. During the regeneration which takes place as in most of the yeasts and moulds, a special study of the extension of the cell wall is made and a possible mechanism for this extension of the regenerated cell wall is proposed.     

元麦叶肉原生质体细胞壁再生过程中的扫描电镜观察及过氧化物酶活性

元麦叶肉原生质体在MS培养基(附加2,4-D 1mg/L,6-BA 0.25 mg/L)中,进行液体浅层培养。用荧光增白剂(VBL)染色,培养1天出现再生壁。通过扫描电镜观察,发现随着培养时间的延长,原生质体表面逐渐出现短棒状突出物和纤维状结构;培养第5天,原生质体表面覆盖较厚的纤维层,与未脱壁的元麦叶肉细胞表面形态结构相似。用愈创木酚作氢供体测定原生质体胞壁再生过程中过氧化物酶活性,发现随着壁再生率提高,过氧化物酶活性明显下降。用聚丙烯酰胺凝胶电泳分离阳极向过氧化物酶同工酶酶谱,酶带也随着培养时间的延长而减少。由刚分离的原生质体中的8条减少到培养4天的2条,反映胞壁再生和过氧化物酶活性呈负相关。     

Modification of protoplast cell wall regeneration by membrane perturbation

Summary Protoplasts derived from cells ofBoergesenia forbesii regenerated aberrant cell walls when treated with cholesteryl hemisuccinate (CHS). Protoplasts treated with CHS, for a short period during the initial stages of cell wall regeneration, developed a patchwork cell wall, possessing regions devoid of cell wall. This effect was reversible, and treated cells ultimately developed a normal, confluent cell wall when removed from the CHS. Freeze fracture studies revealed that for CHS-treated cells, regions without microfibril impressions did possess intramembranous particles (IMP's) but that these regions contained small domains free of IMP's suggestive of lateral phase separation. The data implies that the physical characteristics of the plasma membrane lipid are important to the deposition of cell wall microfibrils during cell wall regeneration. This effect may be attributed to altered lipid-protein interactions, modified membrane fusion characteristics, or altered membrane flow.     

Cell wall enzymatic lysis of the yeast form of Pullularia pullulans and wall regeneration by protoplasts

During the process of degradation of the cell wall of the yeast form of Pullularia pullulans by the lytic system of Micromonospora chalcea samples were withdrawn at different times and observed under phase contrast and electron microscope. The progressive lysis of the walls reveals a fibrillar component inside the apparently amorphous wall. Freeze etched preparations of cells during the formation and regeneration of protoplasts show that the cellular membrane is split and this method allows the smooth external face of the membrane and other internal face covered by particles to be seen. The fact that the smooth face of the membrane is only visible during the preparation or the regeneration of protoplasts and very rarely when intact cells are fractured, suggests a strong adherence between cell wall and this external layer of the membrane. During the regeneration which takes place as in most of the yeasts and moulds, a special study of the extension of the cell wall is made and a possible mechanism for this extension of the regenerated cell wall is proposed.     

3,4-Dehydroproline inhibits cell wall assembly and cell division in tobacco protoplasts.

We investigated the function of cell wall hydroxyproline-rich glycoproteins by observing the effects of a selective inhibitor of prolyl hydroxylase, 3,4-dehydro-L-proline (Dhp), on wall regeneration by Nicotiana tabacum mesophyll cell protoplasts. Protoplasts treated with micromolar concentrations of Dhp do not develop osmotic stability and do not initiate mitosis. The architecture of regenerated cell walls was examined using deep-etch, freeze-fracture electron microscopy of rapidly frozen tobacco cells. Untreated protoplasts assemble a dense fibrillar cell wall consisting of laterally associating subelementary fibrils. In contrast, treatment of protoplasts with Dhp alters the structure of the regenerated wall fibrils in several ways: first, the microfibrils are coated with globular knobs; second, some larger fiber bundles have an open ribbon-like appearance; and third, the smallest subelementary fibrils were not visible. Tobacco cells develop an abnormal morphology as a consequence of this abnormal cell wall structure. Thus, inhibition of prolyl hydroxylase results in the regeneration of a cell wall with abnormal structural and functional properties. These data provide experimental evidence that hydroxyproline-rich glycoproteins are important for the structural integrity of primary cell walls and for the correct assembly of other wall polymers, and that wall structure is an important regulator of cell division and cell morphology.     

Effect of UV-C irradiation on mesophyll protoplasts of Cucumis sativus

In the present work we studied the effect of UV-C irradiation on short-term protoplast physiology, with the aim of identifying and assessing parameters which can provide valuable information for asymmetric fusion experiments. Protoplast viability, cell wall regeneration, density of cell suspension and intensity of DAPI signal were followed by using microscopy and by the detection of specific fluorescent or spectroscopic signals in a microplate reader. The control and irradiated mesophyll protoplasts of Cucumis sativus were used for this experiment. In contrast to control cells, viability of irradiated cells significantly decreased. Intensive cell wall regeneration was observed only in control cells, which also showed significantly higher DAPI fluorescence signal. Microscopy for determination of viability by FDA and cell wall regeneration by Calcofluor White were modified for microplate reader instrumentation. These methods are simple, fast and suitable for detection of the effectiveness of UV-C irradiation of cells intended to be used in asymmetric fusion experiments.     

The Effects of Cell Cycle Parameters on Cell Wall Regeneration and Cell Division of Cotton Protoplasts (Gossypium hirsutum L.)

Protoplasts of cotton cotyledons were isolated and culturedto undergo cell wall regeneration and cell division. DNA contentand cell cycle parameters of nuclei from cotyledons and/or protoplastswere determined by flow cytometry. The DNA content of cotton,Gossypium hirsutum L., was estimated to be 4·34±0·12pg DNA per nucleus. There was a strong positive correlation between G₂ or Sand G₂,and cell wall regeneration and cell division and a strong negativecorrelation between G₁, and cell wall regeneration and celldivision of cotton cotyledon protoplasts. The cell cycle statusof cotyledons changes during their development; as the cotyledonsenlarge, the proportion of cells in G₀ and G₁ phases of thecell cycle increases. The implication of these results in relationto protoplast growth and development is discussed. Key words: Cell cycle parameters, cell wall regeneration, cell division, flow cytometry, Gossypium     

Studies on Chlorella protoplasts

Protoplasts of Chlorella saccharophila (Krüger) Nadson were obtained by cellulase digestion of the microfibrillar inner compount of the cell wall after the resistant outermost layer had been scratched with sea sand. The absence of the cell wall was demonstrated immunologically, electron microscopically and by staining, thus confirming the protoplastic nature of the treated cells. After transfer to an enzyme-free medium regeneration of a thin cell wall was observed. The regeneration of the cell wall obviously followed the same steps as does the cell wall development of the autospores. At least 50% of the protoplasts were able to form colonies when plated on a suitable agar medium.     

Karyokinesis in growing and reverting protoplasts ofSchizosaccharomyces pombe

Division of nuclei without cytokinesis proceeds in growing protoplasts ofSchizosaccharomyces pombe. Prior to regeneration of the complete cell wall and reversion the protoplasts contain 1–7 nuclei, protoplasts with 1–2 nuclei are most frequent. When regeneration of the wall is postponed by adding snail enzymes to the growth medium, protoplasts with a higher number of nuclei (2–4) occur. Multinuclear protoplasts can revert to cells. During the first cytokinesis the protoplast with the regenerated cell wall is divided into two cells by a septum, distribution of nuclei between the two cells being probably incidental. More than only a single nucleus can pass to the revertants even during the second cytokinesis. Septation of protoplasts occurs also during a partial blockage of the wall formation by the snail enzyme preparation, however, reversion to cells can never be observed here (it occurs only after transfer of protoplasts to the medium without the enzyme preparation). The growing and reverting protoplasts represent a very good model system for studying relations among individual processes of the cell cycle, primarily growth of the cell, nuclear cycle and cytokinesis. Yeast protoplasts are often utilized as models for studying morphogenic processes, relations among regeneration of the cell wall, including division of the nucleus (karyokinesis) and cytokinesis.     

Involvement of arabinogalactan proteins in the regeneration process of cultured protoplasts of Marchantia polymorpha

Protoplasts of Marchantia polymorpha L. (liverwort) regenerated new cell walls in initial culture. However, the survival rate of regenerated cells decreased rapidly after this stage. The decrease in survival rate was suppressed by the β-glucosyl Yariv reagent (βglcY), which binds to arabinogalactan proteins (AGPs), only when it was added to culture medium during the period of incipient cell wall regeneration. The addition of βglcY after the period of incipient cell wall regeneration had no effect on the survival rate. These results suggested the involvement of AGPs in the cell wall regeneration process. After cell wall regeneration, the regenerated cells started to divide actively after being transferred to a medium with 1% activated charcoal (AC). Protoplasts that had been cultured with βglcY during the period of incipient cell wall regeneration and then transferred to the AC medium divided vigorously, and the cell division rate was remarkably increased (>80%). However, without transfer to the AC medium, βglcY at concentrations higher than 20 μg ml⁻¹ inhibited cell division. No effect on cell survival nor cell division was observed with the α-galactosyl Yariv reagent. Staining of β-1,3-glucan (callose) with aniline blue (AB) showed that a large amount of β-1,3-glucan was deposited in the regenerated cell walls of the protoplasts cultured without βglcY, while little or no β-1,3-glucan was stained by AB in protoplasts cultured with βglcY. These results suggest that AGPs and β-1,3-glucan play important roles in the survival and subsequent cell division of regenerated cells of M. polymorpha protoplast cultures.     

A study of cell wall regeneration of protoplasts inMarchantia polymorpha L.

Protoplasts ofMarchantia polymorpha L. were isolated from suspension cells. Regeneration of cell walls on the surface of the protoplasts began within a few hr of cultivation. New cell walls completely covered the surface of the protoplasts within 48 hr. Coumarin and 2,6-dichlorobenzonitrile treatment inhibited the formation of the new cell wall. In the initial stage of cell wall regeneration, endoplasmic reticula developed remarkably close to the plasma membrane in the protoplasts, but no development of Golgi bodies was observed at the same locus. This may suggest that the Golgi bodies do not play an active role in the cell wall formation, at least not in very early periods of cell wall regeneration. The development of endoplasmic reticula and an ultrastructural change of plasma membrane from smooth to rough may be important in the cell wall formation of protoplasts.     

Enzyme encapsulation in permeabilized Saccharomyces cerevisiae cells

The Saccharomyces cerevisiae cell wall provides a semipermeable barrier that can retain intracellular proteins but still permits small molecules to pass through. When S. cerevisiae cells expressing E. coli lacZ are treated with detergent to extract the cell membrane, beta-galactosidase activity in the permeabilized cells is approximately 40% of the activity of the protein in cell extract. However, the permeabilized cells can easily be collected and reused over 15 times without appreciable loss in activity. Cell wall composition and thickness can be modified using different cell strains for enzyme expression or by mutating genes involved in cell wall biosynthesis or degradation. The Sigma1278b strain cell wall is less permeable than the walls of BY4742 and W303 cells, and deleting EXG1, which encodes a 1,3-beta-glucanase, can further reduce permeability. A short Zymolyase treatment can increase cell wall permeability without rupturing the cells. Encapsulating multiple enzymes in permeabilized cells can offer kinetic advantages over the same enzymes in solution. Regeneration of ATP from AMP by adenylate kinase and pyruvate kinase encapsulated in the same cell proceeded more rapidly than regeneration using a cell extract. Combining permeabilized cells containing adenylate kinase with permeabilized cells containing pyruvate kinase can also regenerate ATP from AMP, but the kinetics of this reaction are slower than regeneration using cell extract or permeabilized cells expressing both enzymes.     

Experimental inhibition of cell wall formation and of reversion inNadsonia elongata andSchizosaccharomyces pombe protoplasts

Summary The growth, cell wall regeneration, and the reversion of the protoplasts ofNadsonia elongata andSchizosaccbaromyces pombe cultivated in nutrient media containing snail enzyme was studied by light and electron microscopy. The protoplasts grew in the presence of snail enzyme and an incomplete cell wall composed of fibrils was formed on their surface. Thus, the presence of snail enzyme inhibited the completion of cell wall structure and, consequently, the reversion of the protoplasts to normal cells. The transfer of these protoplasts to medium free from snail enzyme led first to the completion of the cell wall and then to the reversion of the protoplasts to normal cells. The reported experiments confirmed that the regeneration of the complete cell wall preceded the protoplast reversion.