SEARCH · PubMed Health

Results for “Mesophyll Cells”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed1995

Actomyosin-based motility of endoplasmic reticulum and chloroplasts in Vallisneria mesophyll cells.

Intracellular localization and motile behaviour of the endoplasmic reticulum (ER), plastids and mitochondria were studied in living mesophyll cells of Vallisneria using the vital fluorochrome 3,3'-dihexyloxacarbocyanine iodide (DIOC6(3)). In quiescent cells, the ER was composed of a three-dimensional network of tubular and lamellar elements. Chloroplasts were distributed evenly throughout the cell periphery and appeared embedded within the ER network. The ER network was relatively stationary, with the exception of rare motile episodes occurring as movement of tubular ER strands and adjacent areas of the polygonal network in localized areas of the cell. During experimental induction of streaming, most of the lamellar ER elements transformed into tubules and together with the chloroplasts they began to translocate to the anticlinal walls to establish the circular streaming around the circumference of the cell. Microwave-accelerated fixation followed by immunofluorescence revealed an hitherto unknown phase of actin reorganization occurring within the cells and most interestingly at the surface of the chloroplasts during streaming induction. Myosin was localized in an ER-like pattern in quiescent as well as in streaming cells, with bright fluorescent label localized on mitochondria and proplastids. In addition, myosin label appeared on the surface of the chloroplasts, preferentially in streaming mesophyll cells. Motile activities were impeded by the actin-depolymerizing drug cytochalasin D (CD), the thioreagent N-ethylmaleimide (NEM), and thapsigargin, an inhibitor of the ER-Ca(2+)-ATPase. These inhibitors also interfered with the integrity of actin filaments, the intracellular distribution of myosin and calcium-homeostasis, respectively. These effects suggested an obligate association of at least one type of myosin with the membranes of ER and smaller organelles and are consistent with the appearance of another type of myosin on the chloroplast surface upon streaming induction.

Actins↗

PubMed2002

Visualization by comprehensive microarray analysis of gene expression programs during transdifferentiation of mesophyll cells into xylem cells.

Plants have a unique transdifferentiation mechanism by which differentiated cells can initiate a new program of differentiation. We used a comprehensive analysis of gene expression in an in vitro zinnia (Zinnia elegans L.) culture model system to gather fundamental information about the gene regulation underlying the transdifferentiation of plant cells. In this model, photosynthetic mesophyll cells isolated from zinnia leaves transdifferentiate into xylem cells in a morphogenic process characterized by features such as secondary-wall formation and programmed cell death. More than 8,000 zinnia cDNA clones were isolated from an equalized cDNA library prepared from cultured cells transdifferentiating into xylem cells. Microarray analysis using these cDNAs revealed several types of unique gene regulation patterns, including: the transient expression of a set of genes during cell isolation, presumably induced by wounding; a rapid reduction in the expression of photosynthetic genes and the rapid induction of protein synthesis-associated genes during the first stage; the preferential induction of auxin-related genes during the subsequent stage; and the transient induction of genes closely associated with particular morphogenetic events, including cell-wall formation and degradation and programmed cell death during the final stage. This analysis also revealed a number of previously uncharacterized genes encoding proteins that function in signal transduction, such as protein kinases and transcription factors that are expressed in a stage-specific manner. These findings provide new clues to the molecular mechanisms of both plant transdifferentiation and wood formation.

Asteraceae↗

PubMed1983

Glyoxylate and glutamate effects on photosynthetic carbon metabolism in isolated chloroplasts and mesophyll cells of spinach.

Addition of millimolar sodium glyoxylate to spinach (Spinacia oleracea) chloroplasts was inhibitory to photosynthetic incorporation of (14)CO(2) under conditions of both low (0.2 millimolar or air levels) and high (9 millimolar) CO(2) concentrations. Incorporation of (14)C into most metabolites decreased. Labeling of 6-P-gluconate and fructose-1,6-bis-P increased. This suggested that glyoxylate inhibited photosynthetic carbon metabolism indirectly by decreasing the reducing potential of chloroplasts through reduction of glyoxylate to glycolate. This hypothesis was supported by measuring the reduction of [(14)C]glyoxylate by chloroplasts. Incubation of isolated mesophyll cells with glyoxylate had no effect on net photosynthetic CO(2) uptake, but increased labeling was observed in 6-P-gluconate, a key indicator of decreased reducing potential. The possibility that glyoxylate was affecting photosynthetic metabolism by decreasing chloroplast pH cannot be excluded. Increased (14)C-labeling of ribulose-1,5-bis-P and decreased 3-P-glyceric acid and glycolate labeling upon addition of glyoxylate to chloroplasts suggested that ribulose-bis-P carboxylase and oxygenase might be inhibited either indirectly or directly by glyoxylate. Glyoxylate addition decreased (14)CO(2) labeling into glycolate and glycine by isolated mesophyll cells but had no effect on net (14)CO(2) fixation. Glutamate had little effect on net photosynthetic metabolism in chloroplast preparations but did increase (14)CO(2) incorporation by 15% in isolated mesophyll cells under air levels of CO(2).

Journal Article↗

PubMed1987

A plasmamembrane redox system and proton transport in isolated mesophyll cells.

Potassium ferricyanide (K(3)Fe[CN](6)) was added to aerated and stirred nonbuffered suspensions of mechanically isolated photosynthetically competent Asparagus sprengeri Regel mesophyll cells. Rates of Fe(CN)(6) (3-) reduction and H(+) efflux were measured with or without illumination. On the addition of 1 millimolar Fe(CN)(6) (3-) to nonilluminated cell suspensions acidification of the medium indicated an H(+) efflux of 1.54 nanomoles H(+)/10(6) cells per minute. Simultaneous Fe(CN)(6) (3-) reduction occurred at a rate of 1.55 nanomoles Fe(CN)(6) (3-)/10(6) cells per minute. Illumination stimulated these rates 14 to 17 times and corresponding values were 26.1 nanomoles H(+)/10(6) cells per minute and 22.9 nanomoles Fe(CN)(6) (3-)/10(6) cells per minute. These two processes appeared to be tightly coupled and were rapidly inhibited when illuminated suspensions were transferred to darkness or treated with 1 micromolar 3-(3,4-dichlorophenyl)-1,1 dimethylurea. Addition of 0.1 millimolar diethylstilbestrol eliminated ATP dependent H(+) efflux in illuminated or nonilluminated cells but had no influence on Fe(CN)(6) (3-) dependent H(+) efflux. Recent reports indicate that a transmembrane redox system spans the plasma membrane of root cells and is coupled to the efflux of H(+). The present report extends these observations to photosynthetically competent mesophyll cells. The results indicate a transport process independent of ATP driven H(+) efflux which operates with a H(+)/e(-) stoichiometry of one.

Journal Article↗

PubMed1999

SbRLK1, a receptor-like protein kinase of Sorghum bicolor (L.) Moench that is expressed in mesophyll cells.

To study the metabolic interactions between mesophyll and bundle-sheath cells of C4 plants, protein kinases possibly involved in the regulatory processes and signal transduction pathways have been cloned and characterized. A receptor-like protein kinase (RLK) cDNA clone from the C4 plant Sorghum bicolor (L.) Moench has been identified. The deduced protein was designated SbRLK1 for receptor-like protein kinase from S. bicolor. The putative cytoplasmic domain of SbRLK1 contains all amino acids that are characteristic of protein kinases. The extracellular domain contains five leucine-rich repeats. The mRNA of the SbRLK1 gene accumulated to much higher levels in mesophyll cells than in the bundle-sheath and was almost undetectable in roots. This expression pattern indicates that SbRLK1 might be involved in the regulation of specific processes in mesophyll cells.

Amino Acid Sequence↗

PubMed2006

Possible association of actin filaments with chloroplasts of spinach mesophyll cells in vivo and in vitro.

In palisade mesophyll cells of spinach (Spinacia oleracea L.) kept under low-intensity white light, chloroplasts were apparently immobile and seemed to be surrounded by fine bundles of actin filaments. High-intensity blue light induced actin-dependent chloroplast movement concomitant with the appearance of a couple of long, straight bundles of actin filaments in each cell, whereas high-intensity red light was essentially ineffective in inducing these responses. The actin organization observed under low-intensity white light has been postulated to function in anchoring chloroplasts at proper intracellular positions through direct interaction with the chloroplasts. Intact chloroplasts, which retained their outer envelopes, were isolated after homogenization of leaves and Percoll centrifugation. No endogenous actin was detected by immunoblotting in the final intact-chloroplast fraction prepared from the leaves kept under low-intensity white light or in darkness. In cosedimentation assays with exogenously added skeletal muscle filamentous actin, however, actin was detected in the intact-chloroplast fraction precipitated after low-speed centrifugation. The association of actin with chloroplasts was apparently dependent on incubation time and chloroplast density. After partial disruption of the outer envelope of isolated chloroplasts by treatment with trypsin, actin was no longer coprecipitated. The results suggest that chloroplasts in spinach leaves can directly interact with actin, and that this interaction may be involved in the regulation of intracellular positioning of chloroplasts.

Actin Cytoskeleton↗

PubMed1977

Rapid isolation of mesophyll cells from leaves of soybean for photosynthetic studies.

Mesophyll cells were rapidly isolated from soybean (Glycine max [L.]) leaves using a combined Macerase enzyme-stirring technique. About 50% to 70% of the leaf cells on a chlorophyll basis from 3 grams of leaves could be isolated in 15 minutes. The cells obtained by this method were capable of high rates of photosynthesis even after storage in the dark for periods of up to 9 hours. The CO(2)-saturated rate of photosynthesis increased from 5 mum CO(2)/mg Chl.hour at 5 C to 170 mum CO(2)/mg Chl.hour at 40 C. At atmospheric CO(2) concentration, the rate varied from 5 to 55 mum CO(2)/mg Chl.hour over this temperature range. The reduced temperature response of photosynthesis at low CO(2) concentration was due to an increased Km(CO(2)) of the cells with increasing temperature. The products of photosynthesis in the isolated cells were similar to the products of leaf photosynthesis.

Journal Article↗

PubMed1987

The Effect of pH, O(2), and Temperature on the CO(2) Compensation Point of Isolated Asparagus Mesophyll Cells.

The effect of pH, O(2) concentration, and temperature on the CO(2) compensation point (capital GHE, Cyrillic[CO(2)]) of isolated Asparagus sprengeri Regel mesophyll cells has been determined in a closed, aqueous environment by a sensitive gas-chromatographic technique. Measured values range between 10 and 100 microliters per liter CO(2) depending upon experimental conditions. The capital GHE, Cyrillic(CO(2)) increases with increasing temperature. The rate of increase is dependent upon the O(2) concentration and is more rapid at high (250-300 micromolar), than at low (30-60 micromolar), O(2) concentrations. The differential effect of temperature on capital GHE, Cyrillic(CO(2)) is more pronounced at pH 6.2 than at pH 8.0, but this pH-dependence is not attributable to a direct, differential effect of pH on the relative rates of photosynthesis and photorespiration, as the O(2)-sensitive component of capital GHE, Cyrillic(CO(2)) remains constant over this range. The capital GHE, Cyrillic(CO(2)) of Asparagus cells at 25 degrees C decreases by 50 microliters per liter when the pH is raised from 6.2 to 8.0, regardless of the prevailing O(2) concentration. It is suggested that the pH-dependence of capital GHE, Cyrillic(CO(2)) is related to the ability of the cell to take up CO(2) from the aqueous environment. The correlation between high HCO(3) (-) concentrations and low capital GHE, Cyrillic(CO(2)) at alkaline pH indicates that extracellular HCO(3) (-) facilitates the uptake of CO(2), possibly by increasing the flux of inorganic carbon from the bulk medium to the cell surface. The strong O(2)- and temperature-dependence of capital GHE, Cyrillic(CO(2)) indicates that isolated Asparagus mesophyll cells lack an efficient means for concentrating intracellular CO(2) to a level sufficient to reduce or suppress photorespiration.

Journal Article↗

PubMed1996

Flow cytometric analysis of cytosolic pH of mesophyll cell protoplasts from the crabgrass Digitaria sanguinalis.

Phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) is a key enzyme of photosynthesis in C4 plants; it is specifically localized in the cytosol of mesophyll cells and is regulated by a phosphorylation/dephosphorylation process. The light-dependent phosphorylation of PEPC is triggered by an increase in the cytosolic pH (pHc) of mesophyll cell protoplasts. An epifluorescence and confocal microscopy analysis showed that the specific pH probe 2',7'-bis-(2-carboxyethyl)-5-(and-6) carboxyfluorescein, acetoxymethyl ester (BCECF-AM), when used at low concentration, was essentially localized in the protoplast cytosol. By the nigericin null-point method and flow cytometry, the pHc of freshly isolated protoplasts was estimated to be 6.4. To observe the full activity of PEPC kinase and maximal phosphorylation of PEPC in vivo, such protoplast suspensions must first be treated with a permeant weak base. The present report shows that 20 mM NH4Cl raised the final pHc to 7.4. This method can be useful for estimating rapid changes of pHc in plant cells.

Ammonium Chloride↗

PubMed1989

Regulation of transplasmalemma electron transport in oat mesophyll cells by sphingoid bases and blue light.

Long-chain sphingoid bases inhibit transplasmalemma electron transport in certain animal cells in part by inhibiting protein phosphorylation. As a first step in determining whether similar regulatory processes exist for cell surface redox activity in plants, peeled leaf segments of Avena sativa L. cv Garry were exposed to sphingoid bases and other long chain lipids. Sphingoid bases which are the most active inhibitors of protein kinase C in animal cells inhibit transplasmalemma electron transport by mesophyll cells in the dark as measured by reduction of exogenous ferricyanide. In white light, however, the same compounds markedly stimulate redox activity. The stimulation by sphingoid bases in the light is not eliminated by the inhibitor of photosynthesis, 3-(3,4-dichlorophenyl)-1,1 dimethylurea (DCMU). Redox activity remaining in the presence of DCMU and sphingoid bases can be observed in blue but not red light. A tentative hypothesis considering the involvement of two separate redox systems is presented in an attempt of explain the disparate action of sphingoid bases on electron transport across the plasmalemma.

Journal Article↗

PubMed1971

Isolation of Mesophyll Cells and Bundle Sheath Cells from Digitaria sanguinalis (L.) Scop. Leaves and a Scanning Microscopy Study of the Internal Leaf Cell Morphology.

A technique is described for the separation of mesophyll and bundle sheath cells from Digitaria sanguinalis leaves and evidence for separation is given with light and scanning electron micrographs. Gentle grinding of fully differentiated leaves in a mortar releases mesophyll cells which are isolated on nylon nets by filtration. More extensive grinding of the remaining tissue yields bundle sheath strands which are isolated by filtration with stainless steel sieves and nylon nets. Further grinding of bundle sheath strands in a tissue homogenizer releases bundle sheath cells which are collected on nylon nets. Percentage of purity derived from cell counts and yield data on a chlorophyll basis are given.The internal leaf cell morphology is presented in scanning electron micrographs and compared with light micrographs of fully-differentiated D. sanguinalis leaves. In leaves of plants which possess the C(4)-dicarboxylic acid cycle of photosynthesis, the relationship of leaf morphology to photosynthesis in mesophyll and bundle sheath cells is considered, and the hypothesis is presented that as atmospheric CO(2) enters a leaf about 85% is fixed by the C(4)-dicarboxylic acid cycle in the mesophyll cells and 10 to 15% is fixed by the reductive pentose phosphate cycle in the bundle sheath cells.A technique also is given for the isolation of mesophyll cells from spinach leaves.

Journal Article↗

PubMed1977

Mesophyll cell protoplasts of potato: isolation, proliferation, and plant regeneration.

Mesophyll cell protoplasts were isolated from potato (Solanum tuberosum L. cv. Russet Burbank) leaves and induced to proliferate in culture. Protoplast division was observed only among preparations isolated from plants previously conditioned under short periods of low intensity illumination. Sustained growth and development of protoplast-derived calli (p-calli) occurred when they were maintained on defined media at 24 C under 500 lux lighting. Shoot bud development within p-calli was controlled by a number of factors including light, temperature, basic medium composition, nature and source of phytohormones, the continued presence of an osmoticum, low concentrations of a utilizable carbohydrate, and the developmental stage of the p-callus.

Journal Article↗

PubMed1988

Kinetics of determination in the differentiation of isolated mesophyll cells of Zinnia elegans to tracheary elements.

Mechanically isolated mesophyll cells of Zinnia elegans L. cv Envy differentiate to tracheary elements when cultured in inductive medium containing 0.5 micromolar alpha-naphthaleneacetic acid and 0.5 micromolar benzyladenine. The cells do not differentiate when cultured in medium in which the concentration of auxin and/or cytokinin has been reduced to 0.005 micromolar. Cells require an initial 24-hour exposure to inductive cytokinin and 56-hour exposure to inductive auxin for differentiation at 72 hours of culture. Freshly isolated Zinnia cells can be maintained in medium having low concentrations of both auxin and cytokinin for only 1 day without significant loss of potential to differentiate upon transfer to inductive medium. Initial culture for up to 2 days in medium having high auxin and low cytokinin, or low auxin and high cytokinin, allows full differentiation on the third day after transfer to inductive medium and potentiates the early differentiation of some cells.

Adenine↗

PubMed1988

l-Glutamate-Dependent Medium Alkalinization by Asparagus Mesophyll Cells : Cotransport or Metabolism?

Mechanically isolated Asparagus sprengeri Regel mesophyll cells cause alkalinization of the suspension medium on the addition of l-glutamate or its analog l-methionine-d,l-sulfoximine. Using a radiolabeled pH probe, it was found that both compounds caused internal acidification whereas l-aspartate did not. Fusicoccin stimulated H(+) efflux from the cells by 111% and the uptake of l-[U-(14)C]glutamate by 55%. Manometric experiments demonstrated that, unlike l-methionine-d,l-sulfoximine, l-glutamate stimulated CO(2) evolution from nonilluminated cells. Simultaneous measurements of medium alkalinization and (14)CO(2) evolution upon the addition of labeled l-glutamate showed that alkalinization was immediate and reached a maximum value after 45 minutes whereas (14)CO(2) evolution exhibited a lag before its appearance and continued in a linear manner for at least 100 minutes. Rates of alkalinization and uptake of l-[U-(14)C]glutamate were higher in the light while rates of (14)CO(2) evolution were higher in the dark. The major labeled product of glutamate decarboxylation, gamma-aminobutyric acid, was found in the cells and the suspension medium. Its addition to the cell suspension did not result in medium alkalinization and evidence indicates that it is lost from the cell to the medium. The data suggest that the origin of medium alkalinization is co-transport not metabolism, and that the loss of labeled CO(2) and gamma-aminobutyric acid from the cell result in an overestimation of the stoichiometry of the H(+)/l-glutamate uptake process.

Journal Article↗

PubMed1981

Phospholipid composition of chlorophyll-free mitochondria isolated via protoplasts from oat mesophyll cells.

Mitochondria were isolated from oat primary leaves via mesophyll protoplasts and subjected to phospholipid analysis. In mesophyll cells mitochondria account for only small proportions of cellular phospholipids (in the order of 5%) and proteins (in the order of 2%). Contamination by lipids from other membranes was insignificant as indicated by the absence or very low levels of chlorophyll, galactolipids and steryl glycosides. The absence of 3-trans-hexadecenoic acid in phosphatidylglycerol from mitochondria of green cells serves an an additional criterion of purity. The phospholipid mixture extracted from these mitochondria resembles phospholipids in mitochondria from non-green tissues regarding composition as well as fatty acid profiles. Therefore, mitochondria maintain a rather constant lipid profile and in contrast to plastids do not respond at this level to differences in the physiological status of their housing cell. Palmitic acid in mitochondrial phosphatidylcholine and phosphatidylethanolamine is primarily localized at the C-1 position of the glycerol moiety. Two enzymatic activities so far not described in mitochondria, formation of acylgalactosyl diacylglycerol and hydrolysis of acyl-CoA, were found in the purified mitochondrial fraction.

Chlorophyll↗

PubMed1996

Differential expression of three genes for different beta-tubulin isotypes during the initial culture of Zinnia mesophyll cells that divide and differentiate into tracheary elements.

Complementary DNA clones for three different beta-tubulin isotypes (ZeTubB1, ZeTubB2 and ZeTubB3) were isolated from a cDNA library generated from RNA of cultured mesophyll cells of Zinnia elegans that were differentiating into tracheary elements and/or dividing. Sequence analysis revealed that the proteins encoded by ZeTubB1 and ZeTubB3 and that encoded by ZeTubB2 were each homologous to two of three groups of beta-tubulin isotypes in Arabidopsis. RNA gel blot analysis of the expression of the ZeTubB transcripts indicated that transcripts that corresponded to each clone were differently expressed during culture of Zinnia mesophyll cells. In particular, the level of expression of ZeTubB1 and ZeTubB3 transcripts increased rapidly prior to cell division and secondary wall formation, and such expression was promoted by combinations of auxin and cytokinin that induced tracheary element differentiation as well as cell division. Results of an in situ hybridization experiment with an antisense RNA probe derived from ZeTubB1 cDNA suggested the preferential expression of ZeTubB transcripts in differentiating xylem cells, as well as in the ground meristem and the procambium, of Zinnia seedlings.

Amino Acid Sequence↗

PubMed1992

Regulatory phosphorylation of phosphoenolpyruvate carboxylase in protoplasts from Sorghum mesophyll cells and the role of pH and Ca2+ as possible components of the light-transduction pathway.

The light-dependent phosphorylation of the photosynthetic phosphoenolpyruvate carboxylase (PyrPC) was shown to occur in protoplasts from Sorghum mesophyll cells. It was accompanied by an increase in PyrPC protein-serine-kinase activity and conferred the target-specific functional properties, i.e. an increase in Vmax and apparent Ki for L-malate, as previously found with the whole leaf. The light-dependent regulatory phosphorylation of PyrPC was (a) specifically promoted by the weak bases NH4Cl and methylamine (agents which increase cytosolic pH), but not by KNO3, (b) inhibited by the cytosolic protein-synthesis inhibitor, cycloheximide, thus confirming that protein turnover is a component of the signal-transduction cascade, as reported in [4], (c) found to moderately decrease in the presence of EGTA and to be strongly depressed when the Ca(2+)-selective ionophore A23187 was added to the incubation medium together with EGTA. Addition of Ca2+, but not of Mg2+, to the Ca(2+)-depleted protoplasts partially, but significantly, relieved the inhibition. Calcium deprivation apparently affected the in-situ light-activation of the PyrPC protein kinase. These data indicated that both Ca2+ and an increase in cytosolic pH are required for the induction of PyrPC protein kinase activity/PyrPC phosphorylation in illuminated protoplasts from Sorghum mesophyll cells.

Amino Acid Sequence↗

PubMed1998

[Ultrastructural differences of RMV and TMV infected Nicotiana tabacum mesophyll cells for distinguishing virus strains].

Nine strains of ribgrass mosaic virus (RMV) and tobacco mosaic virus(TMV) from cruciferous and solanaceous plants in different geographic regions of China were used to inoculate 4-leave-old plants of Nicotiana tobacum for observation of ultrastructually pathological changes due to infection of different strains. The samples of the mesophyll cells of the plants 15 d after inoculation were prepared in a routine and examined using transmission electronic microscopy. Characteristic virion arrangement, inclusion forms, and cell structural aberrations were found different among the various strains. The virions were accumulated in cluster, arranged in ring scattered, irregularly congregated with membrane, and aggregated in angle layer or parallel layer in cytoplasm and vacuoles whereas they were not found in organelles including nuclei, chloroplasts, and mitochondria. The inclusions with bacilliform, club-shaped or granulous X-tubule varied in number and form among the viral strains investigated. The abnormality of cell wall including thickening, collapsing and distortions were also observed among the cells infected by the strains. Other distinguishable changes attributed to the strains included the number, size, shape, and clumping pattern of chloroplasts, and of starch grains and osmiphilic globules chroloplasts of mesophyll cells infected only by two of the 9 strains examined. Additionally, the increased numbers of mitochondria and endoplasmic reticulum were observed in the cells infected by some of the strains. The results indicate that the ultrastructural changes due to viral infection may be useful for distinguishing various RMV and TMV strains.

Microscopy, Electron↗