Hartmut Quader - Academia.edu (original) (raw)
Papers by Hartmut Quader
Journal of Plant Physiology, 1991
ABSTRACT
Journal of Plant Physiology, 1991
ABSTRACT
The endoplasmic reticulum (ER) is a non-uniform compartment in plants as regards its morphology a... more The endoplasmic reticulum (ER) is a non-uniform compartment in plants as regards its morphology and function. It extends as a highly anastomosing membranous network throughout the cytoplasm, is the major compartment of membrane biogenesis, and has been verified to function as the starting site for the secretory pathway. Early electron microscopy studies revealed three morphological ER sub-domains: the smooth ER, the rough
Plant Cell Monographs, 2006
The endoplasmic reticulum (ER) is a non-uniform compartment in plants as regards its morphology a... more The endoplasmic reticulum (ER) is a non-uniform compartment in plants as regards its morphology and function. It extends as a highly anastomosing membranous network throughout the cytoplasm, is the major compartment of membrane biogenesis, and has been verified to function as the starting site for the secretory pathway. Early electron microscopy studies revealed three morphological ER sub-domains: the smooth ER, the rough
Molecular and Cellular Aspects of Calcium in Plant Development, 1986
Protoplasma, 1990
The influence of substances interfering with the cellular calcium distribution on the organizatio... more The influence of substances interfering with the cellular calcium distribution on the organization of the endoplasmic reticulum has been investigated in live epidermal cells of onion bulb scales. The endoplasmic reticulum was visualized by vital staining with the fluorochrome DiOC6(3). It constitutes in these cells an anastomosing membrane system which is composed of three forms: cisternae, short tubules forming a peripheral network, and long tubular strands deeper in the cytoplasm. In the presence of all tested calcium interfering substances, e.g. the ionophore calcimycin (5 gM), the cryptate 221 (0.5 mM), the calmodulin antagonist calmidazolium (10 gM), the tubular ER elements disappear and huge cisternae form instead. The potassium-selective cryptate 222 (1 raM) chemically very similar to the effective cryptate 221 does not cause this change in ER pattern. Actin filaments which are indispensable for ER distribution in the epidermis cells appear to fragment in the presence of the drugs indicating some similarity with the action of cytochalasin D ). Removal of the drugs initiates a characteristic sequence of recovery. The cisternae disintegrate at their edges into tubular loops which are pulled away from this cellular site as long tubular strands. In the presence of cytochalasin D (2 gM) the disintegration of the cisternae is inhibited indicating that kinetic forces are necessary to generate and maintain the spatial distribution of at least parts of the tubular ER meshwork. For the first time the decay of cisternae is described in live cells. The effect of the calcium agents is also compared with changes in ER organization caused by other chemical or natural means.
PLANT PHYSIOLOGY, 1984
The effect of tunicamycin (TM) on the development of the cell wall in Oocystis solitaria has been... more The effect of tunicamycin (TM) on the development of the cell wall in Oocystis solitaria has been investipted. It was found that 10 micromolar TM completely stops the assembly of new microfibrils as observed at the ultrastructural level. During cell wall formation, freeze fracture replicas of the E-face of the plasma membrane reveal two major substructures: the terminal complexes (TC), paired and unpaired, and the microfibril imprints extending from unpaired TCs. In cells treated for 3 hours or longer with TM, the TCs are no longer visible, whereas microfibril imprints are still present. Because of the reported highly selective mode of action of TM, our results implicate a role for Upid-intermediates in cellulose synthesis in 0. solitana. It is assumed that TM prevents the formation of a glycoprotein which probably is a fundamental part of the TCs and may act as a primer for the assembly of the microfibrils.
Protoplasma, 1989
With an improved method to visualize the actin filament system it is possible to detect a small, ... more With an improved method to visualize the actin filament system it is possible to detect a small, peculiar accumulation of aetin filaments under the prospective area of side branch formation in Funaria protonema cells. It consists of a ring-like configuration of actin filaments from which filaments radiate, preferentially along the plasma membrane. During the transition to tip growth the arrangement becomes loosened and eventually disappears whereas the filaments are concentrated in inner regions of the cytoplasm with a maximum in the apical dome.
Physiologia Plantarum, 1994
Stisanne Liebe and Hartmut Quader Liebe, S. and Quader, H, 1994. Myosin in oniou (Altium cepa) bu... more Stisanne Liebe and Hartmut Quader Liebe, S. and Quader, H, 1994. Myosin in oniou (Altium cepa) bulb scale epidermal cells: involvement in dynamics of organelles and endop!a.smic reticulum. -Physiol. Plant. 90: 114-124.
Planta, 1975
The osmotic balance in Ochromonas malhamensis Pringsheim is achieved mainly by formation or degra... more The osmotic balance in Ochromonas malhamensis Pringsheim is achieved mainly by formation or degradation of α-galactosylglycerol (isofloridoside). The time course of the incorporation of radioactivity from (14)CO2 under conditions of high isofloridoside production suggests (Fig. 1) that isofloridoside-phosphate is indeed a precursor in the formation of isofloridoside. To study changes in relative pool sizes of intermediates cell constituents were prelabelled by assimilation of (14)CO2. Upon an increase of osmotic pressure the concentration of isofloridoside-phosphate increases rather rapidly sustaining the above conclusion. The final rate of isofloridoside formation, however, is reached long before the final concentration of the precursor is established (Fig. 2). On a decrease of osmotic pressure isofloridoside-phosphate concentration first increases and than decreases (Fig. 3). The data indicate that control of isofloridoside formation might occur at least at two steps: at the transfer of galactose to glycero-3-phosphate as well as at the dephosphorylation of isofloridoside-phosphate. Under conditions resulting in increased isofloridoside degradation the pool size of free glycerol is rapidly increased about ten fold, whereas the pool of free galactose responds to a far smaller extent (Fig. 3). This might indicate the operation of a transgalactosidase or an α-galactosidase in cooperation with an unusually potent galactose kinase.
J Mol Biol, 2001
The Escherichia coli porin OmpG, which acts as an efficient unspecific channel for mono-, di- and... more The Escherichia coli porin OmpG, which acts as an efficient unspecific channel for mono-, di- and trisaccharides, has been purified and crystallized in two dimensions. Projection maps of two different crystal forms of OmpG at 6 Å resolution show that the protein has a β-barrel structure characteristic for outer membrane proteins, and that it does not form trimers, unlike most other porins such as OmpF and OmpC, but appears in monomeric form. The size of the barrel is ∼2.5 nm, indicating that OmpG may consist of 14 β-strands. The projection map suggests that the channel is restricted by internal loops.
Protoplasma, 2016
Reactive oxygen species (ROS) are emerging players in several biological processes. The present w... more Reactive oxygen species (ROS) are emerging players in several biological processes. The present work investigates their potential involvement in plant cytokinesis by the application of reagents disturbing ROS homeostasis in root-tip cells of Triticum turgidum. In particular, the NADPH-oxidase inhibitor diphenylene iodonium, the ROS scavenger N-acetyl-cysteine, and menadione that leads to ROS overproduction were used. The effects on cytokinetic cells were examined using light, fluorescence, and transmission electron microscopy. ROS imbalance had a great impact on the cytokinetic process including the following: (a) formation of atypical "phragmoplasts" incapable of guiding vesicles to the equatorial plane, (b) inhibition of the dictyosomal and/or endosomal vesicle production that provides the developing cell plates with membranous and matrix polysaccharidic material, (c) disturbance of the fusion processes between vesicles arriving on the cell plate plane, (d) disruption of endocytic vesicle production that mediates the removal of the excess membrane material from the developing cell plate, and (e) the persistence of large callose depositions in treated cell plates. Consequently, either elevated or low ROS levels in cytokinetic root-tip cells resulted in a total inhibition of cell plate assembly or the formation of aberrant cell plates, depending on the stage of the affected cytokinetic cells. The latter failed to expand towards cell cortex and hence to give rise to complete daughter cell wall. These data revealed for the first time the necessity of ROS homeostasis for accomplishment of plant cytokinesis, since it seems to be a prerequisite for almost every aspect of this process.
Journal of Plant Physiology, 1995
European Journal of Protistology, Mar 9, 1990
Cell division in Prorocentrum micans was studied with TEM, SEM and with fluorescence microscope t... more Cell division in Prorocentrum micans was studied with TEM, SEM and with fluorescence microscope techniques to visualize cytoskeletal structures. The cleavage furrow consists of the plasma membrane and two valvar vesicles. Its leading edge is lined with actin filaments. The completion of cytokinesis (like in some other dinoflagellates) is inhibited by extremely low doses of cytochalasin D. Under the influence of this drug cleavage vesicles fuse into large cleavage cavities. New valvae are formed, however, with an irregular, warty surface, caused by a surplus of membrane material and/or lack of stretch and possibly influenced by a predetermined pattern of the cell surface. At the end of mitosis individual or small groups of chromosomes are surrounded by the nuclear envelope.
Protoplasma, 1989
A simple method is introduced to visualize actin filaments in plant cells without previous aldehy... more A simple method is introduced to visualize actin filaments in plant cells without previous aldehyde fixation and/or additional extraction procedures. The concentration dependence of differently modified phallotoxins was examined. Displacement and competition experiments were performed to demonstrate the differences between phallotoxins, unlabeled or labeled with different fluorochromes. The procedure is valid for several plant cells.
Journal of Plant Physiology, 1991
ABSTRACT
Journal of Plant Physiology, 1991
ABSTRACT
The endoplasmic reticulum (ER) is a non-uniform compartment in plants as regards its morphology a... more The endoplasmic reticulum (ER) is a non-uniform compartment in plants as regards its morphology and function. It extends as a highly anastomosing membranous network throughout the cytoplasm, is the major compartment of membrane biogenesis, and has been verified to function as the starting site for the secretory pathway. Early electron microscopy studies revealed three morphological ER sub-domains: the smooth ER, the rough
Plant Cell Monographs, 2006
The endoplasmic reticulum (ER) is a non-uniform compartment in plants as regards its morphology a... more The endoplasmic reticulum (ER) is a non-uniform compartment in plants as regards its morphology and function. It extends as a highly anastomosing membranous network throughout the cytoplasm, is the major compartment of membrane biogenesis, and has been verified to function as the starting site for the secretory pathway. Early electron microscopy studies revealed three morphological ER sub-domains: the smooth ER, the rough
Molecular and Cellular Aspects of Calcium in Plant Development, 1986
Protoplasma, 1990
The influence of substances interfering with the cellular calcium distribution on the organizatio... more The influence of substances interfering with the cellular calcium distribution on the organization of the endoplasmic reticulum has been investigated in live epidermal cells of onion bulb scales. The endoplasmic reticulum was visualized by vital staining with the fluorochrome DiOC6(3). It constitutes in these cells an anastomosing membrane system which is composed of three forms: cisternae, short tubules forming a peripheral network, and long tubular strands deeper in the cytoplasm. In the presence of all tested calcium interfering substances, e.g. the ionophore calcimycin (5 gM), the cryptate 221 (0.5 mM), the calmodulin antagonist calmidazolium (10 gM), the tubular ER elements disappear and huge cisternae form instead. The potassium-selective cryptate 222 (1 raM) chemically very similar to the effective cryptate 221 does not cause this change in ER pattern. Actin filaments which are indispensable for ER distribution in the epidermis cells appear to fragment in the presence of the drugs indicating some similarity with the action of cytochalasin D ). Removal of the drugs initiates a characteristic sequence of recovery. The cisternae disintegrate at their edges into tubular loops which are pulled away from this cellular site as long tubular strands. In the presence of cytochalasin D (2 gM) the disintegration of the cisternae is inhibited indicating that kinetic forces are necessary to generate and maintain the spatial distribution of at least parts of the tubular ER meshwork. For the first time the decay of cisternae is described in live cells. The effect of the calcium agents is also compared with changes in ER organization caused by other chemical or natural means.
PLANT PHYSIOLOGY, 1984
The effect of tunicamycin (TM) on the development of the cell wall in Oocystis solitaria has been... more The effect of tunicamycin (TM) on the development of the cell wall in Oocystis solitaria has been investipted. It was found that 10 micromolar TM completely stops the assembly of new microfibrils as observed at the ultrastructural level. During cell wall formation, freeze fracture replicas of the E-face of the plasma membrane reveal two major substructures: the terminal complexes (TC), paired and unpaired, and the microfibril imprints extending from unpaired TCs. In cells treated for 3 hours or longer with TM, the TCs are no longer visible, whereas microfibril imprints are still present. Because of the reported highly selective mode of action of TM, our results implicate a role for Upid-intermediates in cellulose synthesis in 0. solitana. It is assumed that TM prevents the formation of a glycoprotein which probably is a fundamental part of the TCs and may act as a primer for the assembly of the microfibrils.
Protoplasma, 1989
With an improved method to visualize the actin filament system it is possible to detect a small, ... more With an improved method to visualize the actin filament system it is possible to detect a small, peculiar accumulation of aetin filaments under the prospective area of side branch formation in Funaria protonema cells. It consists of a ring-like configuration of actin filaments from which filaments radiate, preferentially along the plasma membrane. During the transition to tip growth the arrangement becomes loosened and eventually disappears whereas the filaments are concentrated in inner regions of the cytoplasm with a maximum in the apical dome.
Physiologia Plantarum, 1994
Stisanne Liebe and Hartmut Quader Liebe, S. and Quader, H, 1994. Myosin in oniou (Altium cepa) bu... more Stisanne Liebe and Hartmut Quader Liebe, S. and Quader, H, 1994. Myosin in oniou (Altium cepa) bulb scale epidermal cells: involvement in dynamics of organelles and endop!a.smic reticulum. -Physiol. Plant. 90: 114-124.
Planta, 1975
The osmotic balance in Ochromonas malhamensis Pringsheim is achieved mainly by formation or degra... more The osmotic balance in Ochromonas malhamensis Pringsheim is achieved mainly by formation or degradation of α-galactosylglycerol (isofloridoside). The time course of the incorporation of radioactivity from (14)CO2 under conditions of high isofloridoside production suggests (Fig. 1) that isofloridoside-phosphate is indeed a precursor in the formation of isofloridoside. To study changes in relative pool sizes of intermediates cell constituents were prelabelled by assimilation of (14)CO2. Upon an increase of osmotic pressure the concentration of isofloridoside-phosphate increases rather rapidly sustaining the above conclusion. The final rate of isofloridoside formation, however, is reached long before the final concentration of the precursor is established (Fig. 2). On a decrease of osmotic pressure isofloridoside-phosphate concentration first increases and than decreases (Fig. 3). The data indicate that control of isofloridoside formation might occur at least at two steps: at the transfer of galactose to glycero-3-phosphate as well as at the dephosphorylation of isofloridoside-phosphate. Under conditions resulting in increased isofloridoside degradation the pool size of free glycerol is rapidly increased about ten fold, whereas the pool of free galactose responds to a far smaller extent (Fig. 3). This might indicate the operation of a transgalactosidase or an α-galactosidase in cooperation with an unusually potent galactose kinase.
J Mol Biol, 2001
The Escherichia coli porin OmpG, which acts as an efficient unspecific channel for mono-, di- and... more The Escherichia coli porin OmpG, which acts as an efficient unspecific channel for mono-, di- and trisaccharides, has been purified and crystallized in two dimensions. Projection maps of two different crystal forms of OmpG at 6 Å resolution show that the protein has a β-barrel structure characteristic for outer membrane proteins, and that it does not form trimers, unlike most other porins such as OmpF and OmpC, but appears in monomeric form. The size of the barrel is ∼2.5 nm, indicating that OmpG may consist of 14 β-strands. The projection map suggests that the channel is restricted by internal loops.
Protoplasma, 2016
Reactive oxygen species (ROS) are emerging players in several biological processes. The present w... more Reactive oxygen species (ROS) are emerging players in several biological processes. The present work investigates their potential involvement in plant cytokinesis by the application of reagents disturbing ROS homeostasis in root-tip cells of Triticum turgidum. In particular, the NADPH-oxidase inhibitor diphenylene iodonium, the ROS scavenger N-acetyl-cysteine, and menadione that leads to ROS overproduction were used. The effects on cytokinetic cells were examined using light, fluorescence, and transmission electron microscopy. ROS imbalance had a great impact on the cytokinetic process including the following: (a) formation of atypical "phragmoplasts" incapable of guiding vesicles to the equatorial plane, (b) inhibition of the dictyosomal and/or endosomal vesicle production that provides the developing cell plates with membranous and matrix polysaccharidic material, (c) disturbance of the fusion processes between vesicles arriving on the cell plate plane, (d) disruption of endocytic vesicle production that mediates the removal of the excess membrane material from the developing cell plate, and (e) the persistence of large callose depositions in treated cell plates. Consequently, either elevated or low ROS levels in cytokinetic root-tip cells resulted in a total inhibition of cell plate assembly or the formation of aberrant cell plates, depending on the stage of the affected cytokinetic cells. The latter failed to expand towards cell cortex and hence to give rise to complete daughter cell wall. These data revealed for the first time the necessity of ROS homeostasis for accomplishment of plant cytokinesis, since it seems to be a prerequisite for almost every aspect of this process.
Journal of Plant Physiology, 1995
European Journal of Protistology, Mar 9, 1990
Cell division in Prorocentrum micans was studied with TEM, SEM and with fluorescence microscope t... more Cell division in Prorocentrum micans was studied with TEM, SEM and with fluorescence microscope techniques to visualize cytoskeletal structures. The cleavage furrow consists of the plasma membrane and two valvar vesicles. Its leading edge is lined with actin filaments. The completion of cytokinesis (like in some other dinoflagellates) is inhibited by extremely low doses of cytochalasin D. Under the influence of this drug cleavage vesicles fuse into large cleavage cavities. New valvae are formed, however, with an irregular, warty surface, caused by a surplus of membrane material and/or lack of stretch and possibly influenced by a predetermined pattern of the cell surface. At the end of mitosis individual or small groups of chromosomes are surrounded by the nuclear envelope.
Protoplasma, 1989
A simple method is introduced to visualize actin filaments in plant cells without previous aldehy... more A simple method is introduced to visualize actin filaments in plant cells without previous aldehyde fixation and/or additional extraction procedures. The concentration dependence of differently modified phallotoxins was examined. Displacement and competition experiments were performed to demonstrate the differences between phallotoxins, unlabeled or labeled with different fluorochromes. The procedure is valid for several plant cells.