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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)
Endoplasmic reticulum (ER) organization in the dividing cells of the pterophyte Asplenium nidus and of the gymnosperms Pinus brutia and Pinus nigra has been studied by immunolocalization techniques using the monoclonal antibody 2E7, which recognizes luminar ER resident proteins containing C-terminal HDEL sequences. In the pterophyte, the ER reorganization(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)
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 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)
The past three years have witnessed the birth and propagation of a provocative idea in the plant sciences. Its proponents have suggested that higher plants have nerves, synapses, the equivalent of a brain localized somewhere in the roots, and an intelligence. The idea has attracted a number of adherents, to the extent that meetings have now been held in(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 A resolution show that the protein has a beta-barrel structure characteristic for outer membrane proteins, and that it does not(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)
The endoplasmic reticulum (ER) of onion bulb scale epidermis cells consists of long, tubular strands lying deep in the cytoplasm which move quickly and a less mobile peripheral network of tubules and cisternae that change in position, shape and size but that also have immobile, fixed, sites (IFSs). IFSs occur in junctions, at vertexes and at blind endings(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)