Role of nuclear analytical probe techniques in biological trace-element research

Many biomedical experiments require the qualitative and quantitative localization of trace elements with high sensitivity and good spatial resolution. The feasibility of measuring the chemical form of the elements, the time course of trace element metabolism, and conducting experiments in living biological systems are also important requirements for biological trace element research. Nuclear analytical techniques that employ ion or photon beams have grown in importance in the past decade and have led to several new experimental approaches. Some of the important features of these methods are reviewed here along with their role in trace element research. Examples of their use are given to illustrate potential for new research directions. It is emphasized that the effective application of these methods necessitates a closely integrated multidisciplinary scientific team.     

Functional analysis of the Agrobacterium tumefaciens octopine Ti-plasmid left and right T-region border fragments

Summary Border fragments of the octopine Ti-plasmid were tested for their ability to restore tumorigenicity of an avirulent mutant carrying a deleted right border. It was found that neither introduction of left border fragments nor that of small right border fragments at the position of the deletion resulted in a complete restoration of oncogenicity. However, insertion of a larger right border fragment in the deletion mutant gave fully oncogenic strains. In the latter case sequences to the right side of the right border repeat were found to be responsible for a complete restoration of oncogenicity. Also a left border repeat inserted together with this enhancer sequence fully restored the oncogenicity of the deletion mutant. The enhancer-sequence on itself was not able to mediate the transfer of the T-region to the plant cell. Border fragments inserted in inverted orientation in the deletion mutant were able to mediate the transfer of the T-region to the plant cell, but at a reduced frequency.     

Chromosomal nodulation genes: Sym-plasmid containing Agrobacterium strains need chromosomal virulence genes (chvA and chvB) for nodulation

Summary The chromosomal genes chvA and chvB of Agrobacterium tumefaciens, which mediate attachment to plant cells, were found to be essential not only for tumour induction but also for the formation of root nodules on plants.     

Paternal inheritance of chloroplast DNA in Larix

Restriction enzyme analysis was used to determine the inheritance of chloroplast DNA in conifers. The plant material studied included five individual trees of European larch (Larix decidua Mill.) and Japanese larch (Larix leptolepis Sieb. & Zucc.) and six hybrids from controlled crosses between these species. The chloroplast DNA fragment patterns generated by Bam-HI and Bcl-I were species-specific. Paternal inheritance of chloroplast DNA patterns was found in most Larix crosses. One hybrid showed maternal chloroplast DNA patterns. In addition, two other hybrids had mixed Bam-HI patterns suggesting recombination between maternal and paternal chloroplast DNA. The mechanisms favoring paternal inheritance in conifers are not known. Paternal inheritance of chloroplast DNA is suggested it to be a general phenomenon in conifers.     

Plant regeneration from protoplasts of the monocotyledonous Haworthia magnifica v. Poelln.

Calli were initiated from flower buds, gynoecia and inflorescence segments of Haworthia magnifica v. Poelln. and subcultured on solid medium. Two liquid culture steps were necessary to prepare the calli for the isolation of protoplasts capable of sustained cell divisions. Plants were regenerated from protoplast-derived calli. The influence of both the osmolality of the culture media and exudates on the viability of protoplasts and protoplast-derived cell colonies is briefly discussed.     

Somaclonal variation from Sorghum bicolor (L.) Moench cell culture

Plant Cell, Tissue and Organ Culture (PCTOC) - Sorghum bicolor (L.) Moench, plants were regenerated from 4 to 5 month old callus cultures originally derived from seedling explants. Somaclonal...     

Phaseollin production in cell suspensions and whole plants of Phaseolus vulgaris

Production of phaseollin was measured in cell suspension cultures and whole plants of Phaseolus vulgaris. In suspension cultures phaseollin appeared when there was no further increase in cell mass. Cells transferred to a medium without auxins yielded three times higher phaseollin concentrations than cells grown in their presence. Addition of autoclaved fungal mycelia or polysaccharides as elicitors resulted in an increased phaseollin concentration in the cell suspension.In whole plants phaseollin could be detected only after the plants were challenged by a fungus which caused lesions (browning) of the upper root neck region, Rhizoctonia solani. Treatment of non-infected plants with autoclaved fungal mycelia or other elicitors did not induce phaseollin production. However, when they were added before or together with the pathogenic fungus, the elicitors further increased phaseollin concentration in the root neck regions of the plants. This indicated that the pathogenic fungus was important for the penetration of the elicitors to inner plant tissues where phaseollin (and probably other phytoalexins) is produced.     

In vitro proliferation of saffron (Crocus sativus L.) stigma

Excised young intact stigmas plus ovaries of Crocus sativus L. were cultured on Linsmaier-Skoog media supplemented with either a cytokinin or an auxin alone or in combinations. Benzyladenine and kinetin at concentrations of 0.1, 1, and 5 mgl^-1 supported growth, and crocin was biosynthesized in the stigmas in vitro. Auxins had little effect. Young excised single stigmas or half ovaries were also cultured so as to form stigma-like structures in order to explore a possible new approach to industrial production of the spice, saffron. On Linsmaier-Skoog and Nitsch media supplemented with kinetin at concentration of 1 or 5 mgl^-1 and alpha-naphthalene acetic acid or indole-butyric acid at concentration of 0.1 or 10 mgl^-1 in combinations, stigma-like structures appeared directly and indirectly (through meristematic tissue), grew and matured. The maximum number of structures were 75 per half ovary. Three kinds of yellow pigments including crocin were tentatively identified by TLC in the stigma-like structures as was the case for the in vivo grown natural stigma, although the contents were lower.Abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxy-acetic acid - IAA indole-acetic acid - IBA indole-butyric acid - NAA alpha-naphthalene-acetic acid - TLC thin layer chromatography     

Zebra stripes and tiger stripes: the spatial frequency distribution of the pattern compared to that of the background is significant in display and crypsis

Some striped animals are camouflaged in their natural environment, whereas others are conspicuous. Mammals are known to have spatial frequency analysers in their visual mechanism, and it is suggested that the spatial characteristics of a striped pattern are different in camouflaged and conspicuous animals. Fourier analysis of the stripes of the zebra shows spatial frequencies in the pattern that are unlikely to be present so strongly in their natural background scene. A similar analysis of the camouflaging stripes of a tiger show that the distribution of spatial frequencies are similar to that in the background scene.