End-to-end annealing of plant microtubules by the p86 subunit of eukaryotic initiation factor-(iso)4F.

The p86 subunit of eukaryotic initiation factor-(iso)4F from wheat germ exhibits saturable and substoichiometric binding to maize microtubules, induces microtubule bundling in vitro, and is colocalized or closely associated with cortical microtubule bundles in maize root cells, indicating its function as a microtubule-associated protein (MAP). The effects of p86 on the growth of short, taxol-stabilized maize microtubules were investigated. Pure microtubules underwent a gradual length redistribution, an increase in mean length, and a decrease in number concentration consistent with an end-to-end annealing mechanism of microtubule growth.

Function of the p86 subunit of eukaryotic initiation factor (iso)4F as a microtubule-associated protein in plant cells.

The isozyme form of eukaryotic initiation factor 4F [eIF-(iso)4F] from wheat germ is composed of a p28 subunit that binds the 7-methylguanine cap of mRNA and a p86 subunit having unknown function. The p86 subunit was found to have limited sequence similarity to a kinesin-like protein encoded by the katA gene of Arabidopsis thaliana. Native wheat germ eIF-(iso)4F and bacterially expressed p86 subunit and p86-p28 complex bound to taxol-stabilized maize microtubules (MTs) in vitro.

Deficient nucleation during co-polymerization of mammalian MAP2 and tobacco tubulin.

To obtain information on the functional domains of tubulin from a dicot plant, we investigated the interactions of tobacco tubulin with MAP2 from bovine brain supernatant. Taxol-stabilized tobacco and bovine brain microtubules had similar binding capacities for MAP2 (1 mol MAP2 per 8-9 mol tubulin). However, MAP2 dissociated from tobacco microtubules more readily than from bovine brain microtubules and induced the polymerization of tobacco tubulin into aberrant helical ribbon polymers, rather than microtubules.

Competitive Inhibition of High-Affinity Oryzalin Binding to Plant Tubulin by the Phosphoric Amide Herbicide Amiprophos-Methyl.

Amiprophos-methyl (APM), a phosphoric amide herbicide, was previously reported to inhibit the in vitro polymerization of isolated plant tubulin (L.C. Morejohn, D.

Unique functional characteristics of the polymerization and MAP binding regulatory domains of plant tubulin.

An understanding of the regulation of microtubule polymerization and dynamics in plant cells requires biochemical information on the structures, functions, and molecular interactions of plant tubulin and microtubule-associated proteins (MAPs) that regulate microtubule function. We have probed the regulatory domain and polymerization domain of purified maize tubulin using MAP2, an extensively characterized mammalian neuronal MAP. MAP2 bound to the surface of preformed, taxol-stabilized maize microtubules, with binding saturation occurring with one MAP2 molecule per five to six tubulin dimers, as it does with mammalian microtubules.

Rapid and Reversible High-Affinity Binding of the Dinitroaniline Herbicide Oryzalin to Tubulin from Zea mays L.

Oryzalin, a dinitroaniline herbicide, was previously reported to bind to plant tubulin with a moderate strengthe interaction (dissociation constant [Kd] = 8.4 [mu]M) that appeared inconsistent with the nanomolar concentrations of drug that cause the loss of microtubules, inhibit mitosis, and produce herbicidal effects in plants (L.C.

Characterization of the reversible taxol-induced polymerization of plant tubulin into microtubules.

Taxol has been reported to induce the polymerization of plant tubulin into microtubules, albeit weakly when compared to that of mammalian tubulin [Morejohn, L.C., & Fosket, D.

The biochemistry of compounds with anti-microtubule activity in plant cells.

The experimental use of anti-microtubule compounds has revealed essential functions of microtubules in plant cytoskeletal arrays, including the pre-prophase band, the mitotic and meiotic spindles, the phragmoplast, and the cortical array. The most commonly used plant microtubule depolymerization compounds are colchicine, and several synthetic herbicides belonging to three different chemical classes, the dinitroanilines, phosphoric amides, and N-phenyl carbamates. Taxol, a secondary plant product, is the only drug found to promote the polymerization of plant microtubules.

Oryzalin, a dinitroaniline herbicide, binds to plant tubulin and inhibits microtubule polymerization in vitro.

The effects of oryzalin, a dinitroaniline herbicide, on chromosome behavior and on cellular microtubules (MTs) were examined by light microscopy and immunogold staining, respectively, in endosperm cells from Haemanthus katherinae Bak. Brief treatments with 1.0·10(-8) M oryzalin reduced markedly the migration rate of anaphase chromosomes and 1.

Resistance of Rosa microtubule polymerization to colchicine results from a low-affinity interaction of colchicine and tubulin.

The inhibition of the polymerization of tubulin from cultured cells of rose (Rosa. sp. cv.

Inhibition of plant cell proteolytic activities that degrade tubulin.

The requirement for proteinase inhibitors during the chromatographic isolation of tubulin from cultured cells of rose (Rosa sp. cv. Paul's scarlet) was examined by NadodecylSO4-polyacrylamide gel electrophoresis, electron microscopy and immunoblotting.

Taxol-induced rose microtubule polymerization in vitro and its inhibition by colchicine.

Tubulin was isolated from cultured cells of rose (Rosa, sp.cv. Paul's scarlet) by DEAE-Sephadex A50 chromatography, and the taxol-induced polymerization of microtubules in vitro was characterized at 24 degrees C by turbidity development, sedimentation analysis, and electron microscopy.

Inhibition of Plant Microtubule Polymerization in vitro by the Phosphoric Amide Herbicide Amiprophos-Methyl.

The phosphoric amide herbicide amiprophos-methyl (APM) produced a concentration-dependent inhibition of taxol-induced rose microtubule polymerization in vitro. Parallel studies on taxol-induced assembly of bovine brain microtubules showed no effect of APM at a concentration ten times that required to give complete inhibition of rose microtubule assembly. The data indicate that (i) APM is a specific and potent antimicrotubule drug and (ii) APM directly poisons microtubule dynamics in plant cells, rather than indirectly depolymerizing microtubules through a previously proposed mechanism involving deregulation of intracellular calcium levels.

Tubulins from different higher plant species are immunologically nonidentical and bind colchicine differentially.

We have initiated immunological and drug-binding studies on the tubulins from different higher plant species. Antibodies were raised against electrophoretically separated rose (Rosa sp.) tubulin alpha- and beta-subunits and characterized by immunoblot autoradiographic assays.

The tubulins of animals, plants, fungi and protists implications for metazoan evolution.

alpha-Tubulin subunits from trout (S. gairdneri) sperm tails, sea urchin (S. purpuratus) cilia, protistan alga (C.

Differential effects of trypsin on the epidermis of Rana catesbeiana. Observations on differentiating junctions and cytoskeletons.

The filamentous cytoskeletons of epidermal cells of the bullfrog (Rana catesbeiana) were investigated by electron microscopy. Following treatment with trypsin, sheets of epithelium were removed from swatches of abdominal skin. Trypsinization produces differential effects on the ultrastructure of the various cell layers.