A field study of lead phytoextraction by various scented Pelargonium cultivars.

Phytoremediation appears to be a promising technique for metal soil clean up, although its successful application on a large scale still remains a challenge. Field experiments for six scented Pelargonium cultivars, conducted on two Pb-contaminated calcareous and acidic soils, revealed vigorous plant growth, with no symptoms of morpho-phytotoxicity in spite of high Pb accumulation levels. Lead contents in the harvestable parts of all plants grown on the acidic and more contaminated soil were significantly higher than those grown on the calcareous soil. Three cultivars (Attar of Roses, Clorinda and Atomic Snowflake) are Pb-hyperaccumulator plants: they accumulated more than 1,000 mg Pb kg(-1)DW, with high biomass produced.

Effect of atmospheric pressure on sunflower (Helianthus annuus L.) protoplast division.

Sunflower protoplasts were cultured in liquid medium under high atmospheric pressure (0.2 to 0.6 MPa) and the plating efficiency, cell wall synthesis and microtubule organization were assessed. In 7-day-old cultures under a pressure of 0.4 MPa and above, the division rate was strongly reduced by more than 60% as compared to the control. Although most of the protoplasts had begun to regenerate a new cell wall they were unable to complete this process. Pressure also had an inhibitory effect on microtubule synthesis. The percentage of protoplasts showing a disassembled cortical network of microtubules was significantly increased up to 60% of the population. These effects were reversible: when protoplasts were transferred to normal pressure most of them rapidly recovered their capacity to divide and afterwards developed normally. Culturing protoplasts under a pressurized atmosphere revealed to be a good model system for studying cortical microtubule dynamics.

Phleomycin resistance as a dominant selectable marker for plant cell transformation.

Tobacco cells are sensitive to bleomycin and phleomycin. The Tn5 and the Streptoalloteichus hindustanus (Sh) bleomycin resistance ('Ble') genes conferring resistance to these antibiotics have each been inserted into two plant expression vectors. They are flanked by the nopaline synthase (nos) or the cauliflower mosaic virus (CaMV) 35S promoters on one side, and by the nos polyadenylation signal on the other. These four chimaeric genes were introduced into the binary transformation vector pGA 492, which were thereafter mobilized into Agrobacterium tumefaciens strain LBA 4404. The resulting strains were used to transform Nicotiana tabacum cv. Xanthi nc using the leaf disc transformation procedure. In all cases, phleomycin- and bleomycin-resistant tobacco plants were regenerated from transformed cells under selective conditions; however, the highest frequency of rooted plants was obtained when transformation was carried out with the 'Sh Ble' gene under the control of the 35S promoter. Phleomycin resistance was stably transmitted to sexual offspring as a dominant nuclear trait as confirmed by Southern blotting.

Beet necrotic yellow vein virus coat protein-mediated protection in sugarbeet (Beta vulgaris L.) protoplasts.

Transformed Beta vulgaris L. suspension cultures were obtained after cocultivation of sugarbeet cells with Agrobacterium tumefaciens harbouring a binary vector containing the coat protein gene of beet necrotic yellow vein virus inserted between the kanamycin resistance gene and a ß-glucuronidase reporter gene. Protoplasts were isolated both from untransformed cells, and from transformed cells expressing the viral coat protein, and both were then infected with beet necrotic yellow vein virus. Comparison of the levels of infectivity shows that the expression of the coat protein gene in sugarbeet protoplasts mediates high levels of protection against infection by beet necrotic yellow vein virus.

Antigenic analysis of the coat protein of beet necrotic yellow vein virus by means of monoclonal antibodies.

By means of monoclonal antibodies (MAbs), five (groups of) epitopes were identified on particles of beet necrotic yellow vein virus (BNYVV). Epitopes 1 and 2, which were located on the opposite extremities of virus particles, are discontinuous (SDS-labile) epitopes which were destroyed when the particles were treated with trypsin. Epitope 3 is a continuous (SDS-stable) epitope located at the same extremity as epitope 2. It was not destroyed when the particles were treated with trypsin and was present on an Escherichia coli-expressed fusion protein containing amino acids (aa) 1 to 103 of the BNYVV coat protein. The continuous epitope 4, which was located along the entire length of the particles, was found to be present on a fusion protein containing aa 104 to 188 of the BNYVV coat protein but not on trypsin-treated virus particles. In Western blots, these treated particles yielded two slightly smaller coat proteins which failed to react with MAbs specific for epitope 4 but did react with polyclonal antisera and MAbs specific for epitope 3. BNYVV coat protein has a trypsin cleavage site on the carboxyl side of arginine in position 182, so it is therefore suggested that epitope 4 is located on the exposed C terminus, which is composed of aa 183 to 188. Epitope 5 was also located along the entire length of the particles but in a more uneven distribution than epitope 4. This may be because it is a discontinuous epitope that is very sensitive to subtle changes in protein conformation.