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  • Neurospora crassa  (2)
  • Maytenus europaeus  (1)
  • Theobroma cacao  (1)
  • Springer  (4)
  • Nature Publishing Group
  • 1995-1999  (4)
  • 1965-1969
Collection
Publisher
  • Springer  (4)
  • Nature Publishing Group
Years
  • 1995-1999  (4)
  • 1965-1969
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 96 (1998), S. 621-627 
    ISSN: 1432-2242
    Keywords: Key words Cacao ; Theobroma cacao ; Genetic diversity ; Crop evolution ; RAPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Neotropical tree crops are affected by a combination of biological and human factors that complicate the study of genetic diversity and crop evolution. Genetic diversity and relationships among southern Mexican populations and horticultural collections of Theobroma cacao (chocolate, cocoa, cacao) are examined in light of the agricultural practices of the Maya. Collections of cacao were obtained from the extremes of its geographic range including archeological sites in southern Mexico where cacao was first domesticated. Genetic diversity was assayed by 57 informative random amplified polymorphic DNA (RAPD) marker loci. A unique sample of the total diversity found in this study exists in the southern Mexican populations. These populations are significantly different from all other cacao with regards to their profile of RAPD bands, including the ‘criollo’ variety, their morphological and geographical group. A population of cacao found in a sinkhole (cenote) in northern Yucatan with genetic affinities to populations in Chiapas suggests the Maya maintained plants far away from their native habitat. This finding concurs with known agroforestry practices of the Maya. Modern efforts to increase germplasm of tropical tree crops such as cacao should carefully examine archeological sites where genetic diversity, either deliberately or by chance, was collected and maintained by ancient cultures.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Neurospora crassa ; Mitochondria ; Complex I ; Assembly ; Gene disruption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nuclear gene coding for the 20.8-kDa subunit of the membrane arm of respiratory chain NADH:ubiquinone reductase (Complex I) fromNeurospora crassa, nuo-20.8, was localized on linkage group I of the fungal genome. A genomic DNA fragment containing this gene was cloned and a duplication was created in a strain ofN. crassa by transformation. To generate RIP (repeat-induced point) mutations in the duplicated sequence, the transformant was crossed with another strain carrying an auxotrophic marker on chromosome I. To increase the chance of finding an isolate with a non-functionalnuo-20.8 gene, random progeny from the cross were selected against this auxotrophy since RIP of the target gene will only occur in the nucleus carrying the duplication. Among these, we isolated and characterised a mutant strain that lacks the 20.8 kDa mitochondrial protein, indicating that this cysteine-rich polypeptide is not essential. Nevertheless, the absence of the 20.8-kDa subunit prevents the full assembly of complex I. It appears that the peripheral arm and two intermediates of the membrane arm of the enzyme are still formed in the mutant mitochondria. The NADH:ubiquinone reductase activity of sonicated mitochondria from the mutant is rotenone insensitive. Electron microscopy of mutant mitochondria does not reveal any alteration in the structure or numbers of the organelles.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-9710
    Keywords: environmental impact ; Maytenus europaeus ; dunes vegetation ; birds diversity ; restoration of degraded areas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: The development of a greenhouse agriculture in the traditionally impoverished region of Poniente de Almería, on the Mediterranean coast of Spain, has caused an enormous rise in living standards. However, the environmental impact of this badly-planned growth threatens the every dynamics of the exploitation system. A special examination must be made of the use of the three major resources responsible for the functioning of greenhouse production and its impact on the ecosystems and particularly on the vegetation. These resources are: clayey soils, sand from fossil dunes and ground water. While the use of the clayey soils and sand have negative effects on the conservation of ecologically valuable communities found nowhere else in Europe, ground water overexploitation has produced an increase in salinity in most of the aquifers. Of these, sand has been by far the best monitored resource and restoration programmes have been implemented in the extraction zones. This survey deals with the recent evolution of areas where the arto (Maytenus senegalensis subsp. europaeus) and the sabina (Juniperus phoenicea subsp. turbinata) have long been the dominant species, although the presence of the former is nowadays notoriously diminished. The study is based on aerial photographs taken in 1957, 1977 and 1985, together with our own field work. Curiously enough, all this man-made process of degradation has stimulated ornithological diversity. Finally, we propose here some measures which aim to preserve the most important enclaves of these Mediterranean shrub formations, specially those of the arto, since sabina-dominated communities already belong to existing conservation areas.
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  • 4
    ISSN: 1617-4623
    Keywords: Key words Mitochondria ; Complex I ; Gene disruption ; Mutants ; Neurospora crassa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated and characterised the nuclear gene that codes for the 30.4-kDa subunit of the peripheral arm of complex I from Neurospora crassa. The single-copy gene was localised on chromosome VI of the fungal genome by restriction fragment length polymorphism mapping. An extra copy of the gene was introduced into a strain of N. crassa by transformation. This strain was crossed with another strain in order to inactivate, by repeat-induced point mutations, both copies of the duplication carried by the parental transformant. Ascospore progeny from the cross were analysed and a mutant strain lacking the 30.4-kDa protein, nuo30.4, was isolated and further characterised. The mutant appears to assemble the membrane arm of complex I, while formation of the peripheral arm is prevented. Nevertheless, the mutant grows reasonably well – indicating that this well conserved protein is not essential for vegetative growth – and is able to mate with other strains both as male or female. Strains with multiple mutations are readily obtained from heterozygous crosses between different complex I mutants of N. crassa. On the other hand, homozygous crosses between several mutants, including nuo30.4, fail to produce ascospores. These results suggest that complex I plays an essential role during the sexual phase of the life cycle of the fungus.
    Type of Medium: Electronic Resource
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