Hartmut Quader

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The maintenance of a calcium gradient and vesicle secretion in the apex of pollen tubes is essential for growth. It is shown here that phosphatidylinositol-4,5-bisphosphate (PIP2) and D-myo-inositol-1,4,5-trisphosphate (IP3), together with phosphatidic acid (PA), play a vital role in the regulation of these processes. Changes in the intracellular(More)
In plants, tip-growing cells represent an ideal system to investigate signal transduction mechanisms, and among those, pollen tubes are one of the favourite models. Many signalling pathways have been identified during germination and tip growth, namely, Ca2+, calmodulin, phosphoinositides, cyclic AMP, and GTPases. Not surprisingly, the apical secretory(More)
Rapid activation of phospholipase A (PLA) by auxin or plant-pathogen interaction suggests a function in signal transduction for this enzyme, but the molecular identification of a cytosolic PLA carrying out this function remains open. We isolated four cDNA sequences from Arabidopsis (ecotype Columbia), AtPLA I, AtPLA IIA, AtPLA IVA, and AtPLA IVC, which are(More)
In dividing root-tip cells of Pinus brutia Ten., immunolocalization of the luminal endoplasmic reticulum (ER) proteins, which have the C-terminal HDEL sequence, reveals that the ER is reorganized during the preprophase/prophase stage. Portions of ER were arrayed into a ring-like structure at the site of the microtubule preprophase band (Mt-PPB). This(More)
In the epidermal cells of onion (Allium cepa L.) bulb scales the endoplasmic reticulum (ER) can be subdivided into three domains: a peripheral tubular network, cisternae, and long tubular strands. The latter are the form in which the ER is moved in onion cells. During cold treatment the arrangement of the three domains changes drastically. The cisternae and(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(More)
Cortical actin filament (AF) organization was studied in detail in developing stomatal complexes of the grasses Zea mays and Triticum turgidum. AF arrays during the whole stomatal complex development are dynamic, partly following the pattern of cortical microtubule (MT) organization. They also exhibit particular patterns of organization, spatially and(More)
We studied the effect of microgravity on endocytosis in growing tobacco pollen tubes by measuring the plasma membrane retrieval employing the fluorescent phospholipid bis-Bodipy FL C11- phosphatidylcholine as marker. Time course experiments under 1xg condition revealed a localised and relatively fast plasma membrane retrieval in the pollen tube tip region(More)
 Cultured suspension cells of Arabidopsis thaliana that stably express a green-fluorescent protein–α-tubulin 6 fusion protein were used to follow the development and disintegration of phragmoplasts. The development and disintegration of phragmoplasts in the living cultured cells could be successively observed by detecting the green-fluorescent protein(More)
The localization and orientation of cytoskeletal elements in developing cotton fibres were studied by the indirect immunofluorescence and the dry cleaving technique. Microtubules are transversely arranged to the cell axis, most probably in a flat helix, in the cortex of expanding fibres. Since the innermost deposited cellulose microfibrils always show(More)