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Diedrik Menzel

Publications and source records attributed to Diedrik Menzel.

At least 19 recordsLinked to original sources
PubMed2007

Microtubule dynamics in root hairs of Medicago truncatula.

The microtubular cytoskeleton plays an important role in the development of tip-growing plant cells, but knowledge about its dynamics is incomplete. In this study, root hairs of the legume Medicago truncatula have been chosen for a detailed analysis of microtubular cytoskeleton dynamics using GFP-MBD and EB1-YFP as markers and 4D imaging. The microtubular cytoskeleton appears mainly to be composed of bundles which form tracks along which new microtubules polymerise. Polymerisation rates of microtubules are highest in the tip of growing root hairs. Treatment of root hairs with Nod factor and latrunculin B result in a twofold decrease in polymerisation rate. Nonetheless, no direct, physical interaction between the actin filament cytoskeleton and microtubules could be observed. A new picture of how the plant cytoskeleton is organised in apically growing root hairs emerges from these observations, revealing similarities with the organisation in other, non-plant, tip-growing cells.

Actins↗
PubMed2006

Vesicular trafficking, cytoskeleton and signalling in root hairs and pollen tubes.

Root hairs and pollen tubes show strictly polar cell expansion called tip growth. Recent studies of tip growth in root hairs and pollen tubes have revealed that small GTPases of the Rab, Arf and Rho/Rac families, along with their regulatory proteins, are essential for spatio-temporal regulation of vesicular trafficking, cytoskeleton organization and signalling. ROP/RAC GTPases are involved in a multiplicity of functions including the regulation of cytoskeleton organization, calcium signalling and endocytosis in pollen tubes and root hairs. One of the most exciting recent discoveries is the preferential localization of vesicles of the trans-Golgi network (TGN), defined by specific RAB GTPases, in the apical "clear zone" and the definition of TGN as a bona fide organelle involved in both polarized secretion and endocytosis. The TGN is thought to serve the function of an early endosome in plants because it is involved in early endocytosis and rapid vesicular recycling of the plasma membrane in root epidermal cells.

Actins↗
PubMed2006

Functional expression of the green fluorescent protein in the ectomycorrhizal model fungus Hebeloma cylindrosporum.

Hebeloma cylindrosporum is a model fungus for mycorrhizal studies because of its fast growth rate, simple nutritional requirements, and completion of its life cycle in vitro, and because it is amenable to transformation. To advance cell biological research during establishment of symbiosis, a tool that would enable the direct visualisation of fusion proteins in the different symbiotic tissues [namely, the expression of reporter genes such as Green Fluorescent Protein (GFP)] was still a missing tool. In the present study, H. cylindrosporum was transformed using Agrobacterium carrying the binary plasmid pBGgHg containing the Escherichia coli hygromycin B phosphotransferase (hph) and the EGFP genes, both under the control of the Agaricus bisporus glyceraldehyde-3-phosphate dehydrogenase promoter. EGFP expression was successfully detected in transformants. The fluorescence was uniformly distributed in the hyphae, while no significant background signal was detected in control hyphae. The suitability of EGFP for reporter gene studies in Hebeloma cylindrosporum was demonstrated opening up new perspectives in the Hebeloma genetics.

Agrobacterium tumefaciens↗
PubMed2006

Cytokinesis in plant and animal cells: endosomes 'shut the door'.

For many years, cytokinesis in eukaryotic cells was considered to be a process that took a variety of forms. This is rather surprising in the face of an apparently conservative mitosis. Animal cytokinesis was described as a process based on an actomyosin-based contractile ring, assembling, and acting at the cell periphery. In contrast, cytokinesis of plant cells was viewed as the centrifugal generation of a new cell wall by fusion of Golgi apparatus-derived vesicles. However, recent advances in animal and plant cell biology have revealed that many features formerly considered as plant-specific are, in fact, valid also for cytokinetic animal cells. For example, vesicular trafficking has turned out to be important not only for plant but also for animal cytokinesis. Moreover, the terminal phase of animal cytokinesis based on midbody microtubule activity resembles plant cytokinesis in that interdigitating microtubules play a decisive role in the recruitment of cytokinetic vesicles and directing them towards the cytokinetic spaces which need to be plugged by fusing endosomes. Presently, we are approaching another turning point which brings cytokinesis in plant and animal cells even closer. As an unexpected twist, new studies reveal that both plant and animal cytokinesis is driven not so much by Golgi-derived vesicles but rather by homotypically and heterotypically fusing endosomes. These are generated from cytokinetic cortical sites defined by preprophase microtubules and contractile actomyosin ring, which induce local endocytosis of both the plasma membrane and cell wall material. Finally, plant and animal cytokinesis meet together at the physical separation of daughter cells despite obvious differences in their preparatory events.

Actomyosin↗
PubMed2006

Neutral red as a probe for confocal laser scanning microscopy studies of plant roots.

BACKGROUND AND AIMS: Neutral red (NR), a lipophilic phenazine dye, has been widely used in various biological systems as a vital stain for bright-field microscopy. In its unprotonated form it penetrates the plasma membrane and tonoplast of viable plant cells, then due to protonation it becomes trapped in acidic compartments. The possible applications of NR for confocal laser scanning microscopy (CLSM) studies were examined in various aspects of plant root biology. METHODS: NR was used as a fluorochrome for living roots of Phaseolus vulgaris, Allium cepa, A. porrum and Arabidopsis thaliana (wild-type and transgenic GFP-carrying lines). The tissues were visualized using CLSM. The effect of NR on the integrity of the cytoskeleton and the growth rate of arabidopsis primary roots was analysed to judge potential toxic effects of the dye. KEY RESULTS: The main advantages of the use of NR are related to the fact that NR rapidly penetrates root tissues, has affinity to suberin and lignin, and accumulates in the vacuoles. It is shown that NR is a suitable probe for visualization of proto- and metaxylem elements, Casparian bands in the endodermis, and vacuoles in cells of living roots. The actin cytoskeleton and the microtubule system of the cells, as well as the dynamics of root growth, remain unchanged after short-term application of NR, indicating a relatively low toxicity of this chemical. It was also found that NR is a useful probe for the observation of the internal structures of root nodules and of fungal hyphae in vesicular-arbuscular mycorrhizas. CONCLUSIONS: Ease, low cost and absence of tissue processing make NR a useful probe for structural, developmental and vacuole-biogenetic studies of plant roots with CLSM.

Microscopy, Confocal↗
PubMed2005

GFP-FABD2 fusion construct allows in vivo visualization of the dynamic actin cytoskeleton in all cells of Arabidopsis seedlings.

In vivo visualization of filamentous actin in all cells of Arabidopsis thaliana seedlings is essential for understanding the numerous roles of the actin cytoskeleton in diverse processes of cell differentiation. A previously introduced reporter construct based on the actin-binding domain of mouse talin proved to be useful for unravelling some of these aspects in cell layers close to the organ surface. However, cells more deeply embedded, especially stelar cells active in polar transport of auxin, show either diffuse or no fluorescence at all due to the lack of expression of the fusion protein. The same problem is encountered in the root meristem. Recently introduced actin reporters based on fusions between A. thaliana fimbrin 1 and GFP gave brilliant results in organs from the root differentiation zone upwards to the leaves, however failed to depict the filamentous actin cytoskeleton in the transition zone of the root, in the apical meristem and the root cap. To overcome these problems, we have prepared new transgenic lines for the visualization of F-actin in vivo. We report here that a construct consisting of GFP fused to the C-terminal half of A. thaliana fimbrin 1 reveals dynamic arrays of F-actin in all cells of stably transformed A. thaliana seedlings.

Actins↗
PubMed2005

Actin-based motility of endosomes is linked to the polar tip growth of root hairs.

Plant tip growth has been recognized as an actin-based cellular process requiring targeted exocytosis and compensatory endocytosis to occur at the growth cone. However, the identity of subcellular compartments involved in polarized membrane trafficking pathways remains enigmatic in plants. Here we characterize endosomal compartments in tip-growing root hair cells. We demonstrate their presence at the growing tip and differential distribution upon cessation of tip growth. We also show that both the presence of endosomes as well as their rapid movements within the tip region depends on an intact actin cytoskeleton and involves actin polymerization. In conclusion, actin-propelled endosomal motility is tightly linked to the polar tip growth of root hairs.

Actins↗
PubMed2005

The endocytic network in plants.

Endocytosis and vesicle recycling via secretory endosomes are essential for many processes in multicellular organisms. Recently, higher plants have provided useful experimental model systems to study these processes. Endocytosis and secretory endosomes in plants play crucial roles in polar tip growth, a process in which secretory and endocytic pathways are integrated closely. Plant endocytosis and endosomes are important for auxin-mediated cell-cell communication, gravitropic responses, stomatal movements, cytokinesis and cell wall morphogenesis. There is also evidence that F-actin is essential for endocytosis and that plant-specific myosin VIII is an endocytic motor in plants. Last, recent results indicate that the trans Golgi network in plants should be considered an integral part of the endocytic network.

Cell Compartmentation↗
PubMed2005

Plant synapses: actin-based domains for cell-to-cell communication.

For many years it has been known that plants perform rapid long-distance signalling using classical action potentials that have impacts on diverse processes in plants. Plants also synthesize numerous neuronal molecules and fulfill some criteria for intelligent behaviour. Analysis of recent breakthrough data from ecophysiology studies has revealed that plant roots can discriminate between 'self' and 'non-self'; in animals, this ability to discriminate is dependent on the activities of neuronal synapses. Here, we propose that plant cells establish modes of information exchange between each other that have properties in common with neuronal synapses. Moreover, plants also assemble adhesive contacts that orchestrate cell-to-cell communication between the host cells when challenged with pathogens, parasites and potential symbionts. We propose that these adhesive contacts resemble the immunological synapses found in animals.

Action Potentials↗
PubMed2004

The actin-interacting protein AIP1 is essential for actin organization and plant development.

Cell division, growth, and cytoplasmic organization require a dynamic actin cytoskeleton. The filamentous actin (F-actin) network is regulated by actin binding proteins that modulate actin dynamics. These actin binding proteins often have cooperative interactions. In particular, actin interacting protein 1 (AIP1) is capable of capping F-actin and enhancing the activity of the small actin modulating protein, actin depolymerising factor (ADF) in vitro. Here, we analyze the effect of the inducible expression of AIP1 RNAi in Arabidopsis plants to assess AIP1s role in vivo. In intercalary growing cells, the normal actin organization is disrupted, and thick bundles of actin appear in the cytoplasm. Moreover, in root hairs, there is the unusual appearance of actin cables ramifying the root hair tip. We suggest that the reduction in AIP1 results in a decrease in F-actin turnover and the promotion of actin bundling. This distortion of the actin cytoskeleton causes severe plant developmental abnormalities. After induction of the Arabidopis RNAi lines, the cells in the leaves, roots, and shoots fail to expand normally, and in the severest phenotypes, the plants die. Our data suggest that AIP1 is essential for the normal functioning of the actin cytoskeleton in plant development.

Actins↗
PubMed2004

Getting connected: actin-based cell-to-cell channels in plants and animals.

It has been known for more than one hundred years that plant cells are interconnected by cytoplasmic channels called plasmodesmata. This supracellularity was generally considered to be an exotic feature of walled plants containing immobile cells that are firmly enclosed within robust walls. Unexpectedly, intercellular channels in mobile animal cells have been discovered recently. These are extremely dynamic and sensitive to mechanical stress, which causes their rapid breakage and retraction. Both plasmodesmata and nanotubular cell-to-cell channels are supported by the actin cytoskeleton and exclude microtubules. In this article, we discuss the relevance of cell-to-cell channels not only for intercellular communication but also for the development and morphogenesis of multicellular organisms. We also suggest possible parallels between the cell-to-cell transport of endosomes and intracellular pathogens.

Actins↗
PubMed2003

Polar transport of auxin: carrier-mediated flux across the plasma membrane or neurotransmitter-like secretion?

Auxin (indole-3-acetic acid) has its name derived from the Greek word auxein, meaning 'to increase', and it drives plant growth and development. Auxin is a small molecule derived from the amino acid tryptophan and has both hormone- and morphogen-like properties. Although there is much still to be learned, recent progress has started to unveil how auxin is transported from cell-to-cell in a polar manner. Two recent breakthrough papers from Gerd Jürgens' group indicate that auxin transport is mediated by regulated vesicle trafficking, thus encompassing neurotransmitter-like features.

Animals↗
PubMed2003

Class XIII myosins from the green alga Acetabularia: driving force in organelle transport and tip growth?

The green alga Acetabularia cliftonii (Dasycladales) contains at least two myosin genes, which already have been assigned class XIII of the myosin superfamily (Cope et al., 1996, Structure 4: 969-987). Here we report a complete analysis of their gene structure and their corresponding transcripts Aclmyo1 and Aclmyo2. Despite promising Northern blot data no evidence for alternative splicing could be found. Dissecting the primary structure at complementary deoxyribonucleic acid (cDNA) level we found a myosin typical organization in head, neck and variable tail region. Most striking is the extremely short tail region of Aclmyo1 with only 18 residues and the maximum number of 7 IQ motifs in Aclmyo2. Probing Acetabularia protein extracts with an antibody raised to a synthetic peptide derived from the amino terminal region in Alcmyo1 showed cross-reactivity to a polypeptide with a molecular mass of approximately 100 kD. This corresponds to the predicted molecular weight of Aclmyo1, which is 106 kD as deduced from the amino acid sequence. Additionally, the same cross-reactive protein is capable of binding F-actin as indicated by a co-sedimentation assay. Confocal laser scanning microscopy with raised antibody revealed co-localization with organelles, the budding region of lateral whorls and the cell apex suggesting involvement of putative Acetabularia myosin in organelle transport and tip growth.

3' Untranslated Regions↗
PubMed2002

Short-term boron deprivation inhibits endocytosis of cell wall pectins in meristematic cells of maize and wheat root apices.

By using immunofluorescence microscopy, we observed rapidly altered distribution patterns of cell wall pectins in meristematic cells of maize (Zea mays) and wheat (Triticum aestivum) root apices. This response was shown for homogalacturonan pectins characterized by a low level (up to 40%) of methylesterification and for rhamnogalacturonan II pectins cross-linked by a borate diol diester. Under boron deprivation, abundance of these pectins rapidly increased in cell walls, whereas their internalization was inhibited, as evidenced by a reduced and even blocked accumulation of these cell wall pectins within brefeldin A-induced compartments. In contrast, root cells of species sensitive to the boron deprivation, like zucchini (Cucurbita pepo) and alfalfa (Medicago sativa), do not internalize cell wall pectins into brefeldin A compartments and do not show accumulation of pectins in their cell walls under boron deprivation. For maize and wheat root apices, we favor an apoplastic target for the primary action of boron deprivation, which signals deeper into the cell via endocytosis-mediated pectin signaling along putative cell wall-plasma membrane-cytoskeleton continuum.

Boron↗