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  • 1
    Electronic Resource
    Electronic Resource
    Low variability in a Y-linked plant gene and its implications for Y-chromosome evolution (2000)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 404 (2000), S. 388-390 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Sex chromosomes have evolved independently in several different groups of organisms, but they share common features, including genetic degeneration of the Y chromosome. Suppression of recombination between ancestral proto-X and proto-Y chromosomes is thought to have led to their gradual ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35006057
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  • 2
    Electronic Resource
    Electronic Resource
    Polyethylene glycol-mediated direct gene transfer in Nicotiana spp. (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 85 (1992), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Direct gene transfer to protoplasts is a widespread experimental procedure. In this review, it is discussed in relation to the fate and expression of transforming DNA and its genetic transmission upon integration, and expression (in)stability during successive meiotic generations. The results suggest that the major differences between Nicotiana plumbaginifolia and N. tabacum were not in DNA uptake but rather in the specific fate of the transforming DNA. Differences between integrative transformation versus transient gene expression are discussed. Transient gene expression experiments with cotransformed independent constructs enable accurate assays of gene activity modulation, including both activation and repression. The study of the time of integration of foreign DNA using haploid mesophyll protoplasts showed that foreign DNA integration took place during the first two division cycles of the protoplasts. Most of the transfomants inherited the foreign genes as a monogenic trait: N. plumbaginifolia exhibited a higher proportion of multiple insertions compared with N. tabacum. Furthermore, gene integration occurs as a random process. Compared to ‘simple’ transformation, cotransformation with independent constructs showed a higher level of rearrangement of the inserted DNA. Foreign gene transmission, followed through different generations, indicated that inactivation of the inserted gene could happen through a variety of processes. These results open up a series of questions concerning the applied aspects of direct gene transfer to plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1992.tb04745.x
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  • 3
    Electronic Resource
    Electronic Resource
    Sex organ determination and differentiation in the dioecious plant Melandrium album (Silene latifolia): a cytological and histological analysis (1997)
    Springer
    Sexual plant reproduction 10 (1997), S. 155-167 
    Details
    ISSN: 1432-2145
    Keywords: Key words Dioecious plant ; Melandrium album ; Development ; Sex determination ; Organ differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Melandrium album (Silene alba) is a dioecious plant with heteromorphic sex chromosomes (XY system). Sexual dimorphism is a result of developmental blocks in male or female reproductive organ formation within young bipotential flower buds. Progress in understanding the genetic and molecular mechanisms controlling sex determination in this species relies on a detailed description of developmental timing in the two sexes, with emphasis on those early stages during which sexual dimorphism is established. We used a combination of histological and scanning electron microscopy analysis to refine the comparative study and description of the staging of male compared to female flower development. We show that (1) female dimorphism results from modifications in flower meristem organisation, namely a sudden arrest of cell divisions in whorl 4 of male flowers at the time when meristem partitioning is achieved between whorls 3 and 4, and (2) male dimorphism is part of the stamen differentiation process corresponding to stamen arrest at the early sporogenous stage in female flowers. Thus, Melandrium is a natural double ”mutant” that is affected in very early and distinct processes of reproductive organ differentiation. Our results are used to discuss the most likely nature of the specific functions controlling sexual dimorphism in Melandrium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050083
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  • 4
    Electronic Resource
    Electronic Resource
    Yeast RAS2 affects cell viability, mitotic division and transient gene expression in Nicotiana species (1990)
    Springer
    Plant molecular biology 14 (1990), S. 669-685 
    Details
    ISSN: 1573-5028
    Keywords: Nicotiana ; plant protoplasts ; RAS2 ; suicide gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Overexpression of the budding yeast RAS2 gene in Nicotiana plumbaginifolia cells revealed that RAS2 acted as a ‘suicide’ gene in freshly isolated protoplasts from leaves and blocked cell proliferation in cell suspension-derived protoplasts. Among a series of genes tested (such as npt II, CDC35, PDE2), RAS2 was the only one to block the expression of the cat gene, as measured in a transient gene expression assay. Another ras gene, v-Ha-ras, had similar effects. Furthermore, the RAS2 effect was species-specific and depended on the modulation of hormonal metabolism in the transfected cells, while no differences were noticed between the normal and the activated val19 gene. Transfected plant cells are shown to synthesize a RAS2 protein of the same electrophoretic mobility as the yeast RAS2 product. The results are discussed in the broader context of the evolutionarily conserved ras genes involved in vital cellular functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016500
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  • 5
    Electronic Resource
    Electronic Resource
    Progress in cellular engineering of plants: biochemical and genetic assessment of selectable markers from cultured cells (1984)
    Springer
    Plant molecular biology 3 (1984), S. 289-302 
    Details
    ISSN: 1573-5028
    Keywords: selectable markers ; biochemical and genetic analysis ; alien gene introgression ; egg transformation ; protoplast fusion ; irradiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Recent availability of stable and well characterized selectable markers and ability to combine alien genomes parasexually have contributed to the development of molecular biology in higher plants, including gene expression and genetic manipulation. Several types of biochemical mutants (resistant to inhibitory concentrations of aminoacid(s) or aminoacid analogs as well as deficient for enzyme activity) have recently been isolated and characterized biochemically and genetically. Among them, mutants with alterations in the nitrogen and aminoacid metabolism, or in the activity of alcohol dehydrogenases are being used in the development of more efficient techniques of gene transfer. The manipulation of whole genomes by sexual or somatic cell fusion offers new potential in this field, but refinement of transfer techniques is desirable. The new set of selectable markers obtained through advanced cellular technology, as well as our ability to regenerate plants from manipulated cell lines are expected to play a major role in cellular engineering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017783
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  • 6
    Electronic Resource
    Electronic Resource
    Biochemical characterisation of Nicotiana plumbaginifolia auxotrophs that require branched-chain amino acids (1986)
    Springer
    Plant cell reports 5 (1986), S. 223-226 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The biochemical lesions in six amino acid-requiring auxotrophic lines of Nicotiana plumbaginifolia have been investigated, by means of feeding experiments with [14C] and unlabelled substrates, and enzyme analysis. Three of the lines require isoleucine for growth, are unable to synthesise 2-oxobutyrate in vivo and have no detectable threonine dehydratase (E.C.4.2.1.16) in vitro. The other three lines require (isoleucine + valine), accumulate [14C] dihydroxymethylvalerate when fed [14C]-L-threonine, and contain no detectable dihydroxyacid dehydratase (E.C.4.2.1.9).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00269125
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  • 7
    Electronic Resource
    Electronic Resource
    DNA methylation of sex chromosomes in a dioecious plant, Melandrium album (1993)
    Springer
    Molecular genetics and genomics 239 (1993), S. 219-224 
    Details
    ISSN: 1617-4623
    Keywords: DNA methylation ; In situ nick-translation ; Lyon hypothesis ; Sex chromosomes ; Melandrium album
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Melandrium album, a dioecious plant species, has two heteromorphic sex chromosomes with the XY constitution typical for male and the XX for female plants. This plant represents an experimental model system of sex determination in which the Y chromosome plays a strongly dominant male role. We present data on the overall transcriptional activities of M. album sex chromosomes. DNA methylation patterns were analysed directly at the level of chromosomes using in situ nick-translation of fixed root mitotic chromosomes after nuclease digestion and in vivo labelling with S-adenosyl-l-[methyl-3H] methionine as donor of methyl groups. Both techniques revealed that the two X chromosomes of female plants had different levels of DNA methylation. Cell treatment with a DNA hypomethylating drug, 5-azacytidine, significantly influenced the labelling densities. These results imply that in female M. album plants, one of the two X chromosomes may be hypermethylated and inactive as described for mammalian cells (Lyon hypothesis). A similar analysis made on male cells displayed a similar relative levels of methylation in autosomes and sex chromosomes, thus indicating the transcriptional activity of both Y and X male chromosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00281621
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  • 8
    Electronic Resource
    Electronic Resource
    A floral third whorl-specific marker gene in the dioecious species white campion is differentially expressed in mutants defective in stamen development (1997)
    Springer
    Plant molecular biology 35 (1997), S. 1009-1014 
    Details
    ISSN: 1573-5028
    Keywords: anther ; clone CCLS4 ; dioecious ; parietal cells ; Silene latifolia ; third whorl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The CCLS4 gene of white campion is specifically expressed in anther epidermis and endothecium from pre- to post-meiotic stages. We report on a detailed in situ analysis of the gene's expression and show that it is a marker of the floral third whorl. The gene is expressed (1) in the anther (epidermis, parietal cells and the derived endothecium) in normally developing stamens and (2) in distinct sub-domains of third-whorl epidermis in mutants exhibiting aberrant states of parietal differentiation. Our results suggest that CCLS4 may fulfil different functions during pre- and post-meiotic anther development and reveal the complex role parietal cells may play during early stamen formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005864403221
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