Joop E. M. Vermeer

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Phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] functions as a site-specific signal on membranes to promote cytoskeletal reorganization and membrane trafficking. Localization of PtdIns(4,5)P2 to apices of growing root hairs and pollen tubes suggests that it plays an important role in tip growth. However, its regulation and mode of action remain(More)
Polarized expansion of root hair cells in Arabidopsis thaliana is improperly controlled in root hair-defective rhd4-1 mutant plants, resulting in root hairs that are shorter and randomly form bulges along their length. Using time-lapse fluorescence microscopy in rhd4-1 root hairs, we analyzed membrane dynamics after labeling with RabA4b, a marker for(More)
Polyphosphoinositides (PPIs) became famous for their role in inositol-1,4,5-trisphosphate (InsP3) mediated-Ca(2+) signalling in mammalian cells, generated through signal-activated phospholipase C (PLC) hydrolysis of the minor membrane lipid, phosphatidylinositol-4,5-bisphosphate. For many years, the plant field followed the same paradigm, however, slowly a(More)
The regulation of pH in cellular compartments is crucial for intracellular trafficking of vesicles and proteins and the transport of small molecules, including hormones. In endomembrane compartments, pH is regulated by vacuolar H+-ATPase (V-ATPase), which, in plants, act together with H+-pyrophosphatases (PPase), whereas distinct P-type H+-ATPases in the(More)
Polarized epithelia are fundamental to multicellular life. In animal epithelia, conserved junctional complexes establish membrane diffusion barriers, cellular adherence and sealing of the extracellular space. Plant cellular barriers are of independent evolutionary origin. The root endodermis strongly resembles a polarized epithelium and functions in(More)
Summary There is evidence that the necrotrophic fungal pathogen Botrytis cinerea is exposed to oxidative processes within plant tissues. The pathogen itself also generates active oxygen species and H(2)O(2) as pathogenicity factors. Our aim was to study how the pathogen may defend itself against cellular damage caused by the accumulation of H(2)O(2) and the(More)
Lateral root formation in plants can be studied as the process of interaction between chemical signals and physical forces during development. Lateral root primordia grow through overlying cell layers that must accommodate this incursion. Here, we analyze responses of the endodermis, the immediate neighbor to an initiating lateral root. Endodermal cells(More)
Heat stress induces an array of physiological adjustments that facilitate continued homeostasis and survival during periods of elevated temperatures. Here, we report that within minutes of a sudden temperature increase, plants deploy specific phospholipids to specific intracellular locations: phospholipase D (PLD) and a phosphatidylinositolphosphate kinase(More)
To investigate PtdIns3P localization and function in plants, a fluorescent PtdIns3P-specific biosensor (YFP-2xFYVE) was created. On lipid dot blots it bound specifically and with high affinity to PtdIns3P. Transient expression in cowpea protoplasts labelled vacuolar membranes and highly motile structures undergoing fusion and fission. Stable expression in(More)
Polyphosphoinositides represent a minor group of phospholipids, accounting for less than 1% of the total. Despite their low abundance, these molecules have been implicated in various signalling and membrane trafficking events. Phosphatidylinositol 4-phosphate (PtdIns4P) is the most abundant polyphosphoinositide. (32)Pi-labelling studies have shown that the(More)