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  • 1
    Electronic Resource
    Electronic Resource
    Preparation and fusion properties of protoplasts from mature pollen of Nicotiana tabacum (1995)
    Springer
    Plant cell reports 14 (1995), S. 199-203 
    Details
    ISSN: 1432-203X
    Keywords: Nicotiana tabacum ; Pollen protoplast ; Mesophyll protoplast ; Protoplast fusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A method to remove the exine from mature tobacco pollen and to release numerous intact pollen protoplasts has been developed. Post-anthesis binucleate pollen was treated with water, buffered with MES at pH 5.5, for two hours. Rupture of the exine was caused by the force of pollen hydration exposing the intine to subsequent enzymatic maceration. The high osmotic pressure (1000 mOsm·kg-1 H2O) of pollen protoplasts required a special maceration medium, 4% KCl (w/v). Action of an enzyme solution containing 1% (w/v) Macerozyme and 1% (w/v) Cellulase gave rise to viable protoplasts within 4 hours. When cultured in a tobacco mesophyll protoplast culture medium, the pollen protoplasts underwent regeneration of a cell wall, formation of various tube-shaped structures, and division of the generative nucleus into two nuclei. Using a PEG/Ca2+ method pollen protoplasts were fused with diploid mesophyll protoplasts. Evidence of transfer of chloroplasts into the pollen protoplasts was observed after one day of culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233633
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  • 2
    Electronic Resource
    Electronic Resource
    Amino-acid-transport mutant of Nicotiana tabacum L. (1985)
    Springer
    Planta 166 (1985), S. 141-144 
    Details
    ISSN: 1432-2048
    Keywords: Amino acid uptake ; Leaf (amino acid uptake) ; Mutant (valine-resistant) ; Nicotiana (amino acid transport) ; Transport (membrane) ; Valine resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The uptake rates of 16 amino acids were measured in leaf discs from Nicotiana tabacum L., cv. Xanthi (wild type) and from two valine-resistant mutants, Valr-1 and Valr-2. For all amino acids tested the uptake rates in Valr-1 were similar to those in the wild type. The Valr-2 mutant showed a reduced uptake of neutral and acidic amino acids, but uptake of the basic amino acids was only slightly lower than in the wild type. It is argued that two systems for amino-acid transport are present: one for neutral and acidic amino acids and the other for basic amino acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397397
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  • 3
    Electronic Resource
    Electronic Resource
    Altered feedback sensitivity of acetohydroxyacid synthase from valine-resistant mutants of tobacco (Nicotiana tabacum L.) (1986)
    Springer
    Planta 169 (1986), S. 46-50 
    Details
    ISSN: 1432-2048
    Keywords: Acetohydroxyacid synthase ; Amino acid (branched-chain) ; Feedback regulation ; Mutant (Nicotiana) ; Nicotiana ; Valine resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acetohydroxyacid synthase (EC 4.1.3.18) has been extracted from leaves of three valine-resistant (Valr) tobacco (Nicotiana tabacum) mutants, and compared with the enzyme from the wild-type. The enzyme from all three mutants is appreciably less sensitive to inhibition by leucine and valine than the wild-type. Two of the mutants, Valr-1 and Valr-6, have very similar enzymes, which under all conditions are inhibited by less than half that found for the wild-type. The other mutant, Valr-7, has an enzyme that only displays appreciably different characteristics from the wild-type at high pyruvate or inhibitor concentrations. Enzyme from Valr-7 also has a higher apparent Km for pyruvate, threefold greater than the value determined for the wild-type and the other mutants. The sulphonylurea herbicides strongly inhibit the enzyme from all the lines, though the concentrations required for half-maximal inhibition of enzyme from Valr-1 and Valr-6 are higher than for Valr-7 or the wildtype. No evidence has been found for multiple isoforms of acetohydroxyacid synthase, and it is suggested that the valine-resistance of these mutant lines is the result of two different mutations affecting a single enzyme, possibly involving different subunits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01369774
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  • 4
    Electronic Resource
    Electronic Resource
    Cellular genetic study of a somatic instability in a tobacco mutant: in vitro isolation of valine-resistant spontaneous mutants (1989)
    Springer
    Theoretical and applied genetics 77 (1989), S. 482-488 
    Details
    ISSN: 1432-2242
    Keywords: Somatic instability ; Valine resistance ; Nicotiana tabacum ; Protoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A chlorophyll-deficient mutant line of tobacco (Nicotiana tabacum), named tl, displays spontaneously on leaves green, white, and twinned green/white somatic variations at high frequencies (10−3 to 10−2). The frequency of cell events leading to the somatic variations has been shown to be closely dependent on the stage of differentiation of cells during plant development. The activity of transposable elements is suspected in the tl genotype, and a study of its mutagenic ability was performed by selecting in vitro new mutant cellular types. The cellular marker chosen was the resistance to toxic doses of valine conferred by a permeation deficiency. A reproducible method allowing efficient selection of valine-resistant mutant clones from haploid tobacco mesophyll protoplast-derived cells was used. In 10 out of 12 experiments, the frequency of spontaneous valine-resistant clones obtained with the wild-type control was null for cell populations tested to the 106. On the other hand, spontaneous valine-resistant clones were repeatedly isolated at variable and sometimes high frequencies (greater than 10−3) from cell populations of the tl type. Valine resistance of plants regenerated from these clones was transmitted to the progeny as a single monogenic mutation. These results indicate an increased mutagenic ability of the tl genotype, as compared to the wild-type line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00274267
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  • 5
    Electronic Resource
    Electronic Resource
    Selection for spontaneous tomato haploids using a conditional lethal marker (1993)
    Springer
    Theoretical and applied genetics 86 (1993), S. 657-664 
    Details
    ISSN: 1432-2242
    Keywords: Tomato ; Haploid ; Selectable marker ; Indole acetamide/naphthalene acetamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We describe a method for the isolation of spontaneous haploid tomato plants from greenhousegrown seedlings obtained from crosses involving a transgenic parental line in which a counter-selectionable chimeric gene has been introduced. Transgenic seeds transformed with the aux2 gene, a gene of Agrobacterium rhizogenes that transforms naphthalene acetamide (NAM) into naphthalene acetic acid (NAA), did not develop roots in the presence of NAM, whereas wildtype tomato seeds developed a normal rooting system in its presence. Transgenic plants homozygous for aux2 (cv ‘UC82b’) were used to pollinate male-sterile (ms322) tomato plants (cv ‘Apedice’). Using NAM as a toxic substrate to kill heterozygous diploid plants carrying aux2, we selected for three maternal haploid plants resulting from the development of the female nucleus without fertilization. Maternal haploid selection using the aux2 marker was less efficient than the visual screening of haploid plants displaying recessive morphological markers of the female parent, but provided evidence for the feasibility of haploid selection in species for which no morphological markers are available.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222653
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  • 6
    Electronic Resource
    Electronic Resource
    Direct selection of cybrids by streptomycin and valine resistance in tobacco (1986)
    Springer
    Theoretical and applied genetics 72 (1986), S. 11-14 
    Details
    ISSN: 1432-2242
    Keywords: Cybrid ; Streptomycin resistance ; Valine resistance ; Tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Direct selection of cybrids by simultaneous selection for “donor” chloroplasts and for the “recipient” nuclei is described. Mesophyll protoplasts of two tobacco (Nicotiana tabacum) mutants, SR1 (streptomycin resistant) and Valr-2 (valine resistant), were fused by polyethylene glycol treatment. Streptomycin resistance in the SR1 mutant is a maternally inherited chloroplast trait while valine resistance is a Mendelian (nuclear) digenic recessive character. The fused protoplast population was cultured and colonies were selected for resistance to valine (1 mM) and streptomycin (343 μM). The efficiency of selection has been confirmed in three clones by demonstrating seed transmission of both streptomycin and valine resistances. In one subclone both streptomycin resistant and sensitive plants were obtained indicating that the streptomycin sensitive chloroplasts had not been totally eliminated by growth on the selective medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261447
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  • 7
    Electronic Resource
    Electronic Resource
    Sexual and somatic hybridization in the genusLycopersicon (1993)
    Springer
    Theoretical and applied genetics 86 (1993), S. 533-546 
    Details
    ISSN: 1432-2242
    Keywords: Lycopersicon ; Sexual hybridization ; Somatic hybridization ; Cybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In recent years, a large number of reports have been published on the recovery of somatic hybrids in the genusLycopersicon and their potential use as a tool in plant breeding programs. Somatic hybridization as a way of enabling the incompatibility barriers which exist within the genusLycopersicon to be bypassed has attracted great interest. WildLycopersicon species harbor numerous interesting agronomic characteristics, which could be transferred to tomato by somatic hybridization. In particular, the production of asymmetric hybrids is explored as an approach to obtain the transfer of only a part of the nuclear genome of wildLycopersicon species. Considerable information is available on the fate of chloroplasts and mitochondria in fusion products inLycopersicon, and unfortunately, cybridization (transfer of chloroplasts and/or mitochondria) seems often difficult to achieve.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00838706
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