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  • 1
    Electronic Resource
    Electronic Resource
    Quantitative cytology of the sperm cells of Brassica campestris and B. oleracea (1987)
    Springer
    Planta 170 (1987), S. 446-452 
    Details
    ISSN: 1432-2048
    Keywords: Brassica (sperm cell) ; Cytoplasmic inheritance ; Double fertilization ; Mitochondrion ; Pollen ; Vegetative nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pollen grains of Brassica campestris L. var. acephala DC and B. oleracea L. were serially sectioned and examined using transmission electron microscopy to determine the three-dimensional organization of sperm cells within the microgametophyte and the quantity of membrane-bound organelles occurring within each cell. Sperm cells occur in pairs within each pollen grain, but are dimorphic, differing in size, morphology and mitochondrial content. The larger of the two sperm cells (Svn) is distinguished by the presence of a blunt evagination, which in B. oleracea wraps around and lies within shallow furrows on the vegetative nucleus and in B. campestris can penetrate through internal enclaves of the vegetative nucleus. This sperm cell contains more mitochondria in both species than the second sperm cell (Sua). This latter cell is linked to the first by a common cell junction with the S vn, but is not associated with the vegetative nucleus and lacks a cellular evagination. Such differences are indicative of a system of cytoplasmic heterospermy in which sperm cells possess significantly different quantities of mitochondria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402978
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative, three-dimensional ultrastructure of isolated corn (Zea mays) sperm cells (1990)
    Springer
    Protoplasma 153 (1990), S. 136-140 
    Details
    ISSN: 1615-6102
    Keywords: Cytoplasmic inheritance ; Organelle distribution ; Preferential fertilization ; In vitro fertilization ; Zea mays pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Five isolatedZea mays sperm cells, taken from the same population as used for a previous morphometric study, were serially ultrathin sectioned and computer-reconstructed to yield three-dimensional images as well as quantitative data. All cells were found to be essentially spherical and to contain a full complement of cell constituents except plastids and microtubules. The nuclei of three cells were highly curved into a “C” or “V” shape while the other two nuclei were not curved, but were more spherical to disc shaped. The three curved nuclei were heterochromatic in appearance, the other two were more euchromatic. Mitochondria were closely associated with the nuclei, were predominately in the form of large, variously shaped complexes, and ranged in number from 7 to approximately 74 per cell. Dictyosomes tended not to be close to the nucleus and ranged in number from 6 to 23 per cell. The endoplasmic reticulum was similarly not typically associated with the nucleus, and varied from extensive sheet-like areas to small membranous whorls. In addition to confirming the findings of previous studies on isolated corn sperm cells and providing new three-dimensional and distribution data, the results of the present work underscore the existence of a high degree of morphological variability amongZea mays sperm cells of a population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01353997
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  • 3
    Electronic Resource
    Electronic Resource
    Organization of the early post-fertilization megagametophyte ofPopulus deltoides (1990)
    Springer
    Protoplasma 155 (1990), S. 153-165 
    Details
    ISSN: 1615-6102
    Keywords: Cytoplasmic inheritance ; Female germ unit ; Fertilization ; Gametic fusion mechanisms ; Male gamete ; Populus ; Synergid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Gynoecia ofPopulus deltoides, 48 to 60 h after pollination, were examined using transmission electron microscopy. The mature megagametophyte contains two synergids, an egg cell, a central cell with two unfused polar nuclei and three antipodals. Pollen tube passage between cells in the styloid, on the placenta and through the micropyle does not induce degeneration of surrounding cells. Pollen tube entry into the megagametophyte occurs through the degenerated synergid immediately adjacent to the filiform apparatus. The tube grows the length of the filiform apparatus 20–30 μm into the synergid, and then discharges its contents-two sperm cells, the vegetative nucleus, and pollen tube cytoplasm. Sperm cells appear progressively hypertrophied during their passage in the pollen tube. In the degenerate synergid, the sperm nucleus is located at one end of the cell and the remaining cytoplasm is diffuse, containing a large vacuole. Following transmission of sperm nuclei into the egg and central cell, one male nucleus fuses with the egg and the other fuses with the micropylar polar nucleus. Enucleate cytoplasmic bodies of apparent sperm origin were observed within the degenerated synergid. The gametic fusion mechanism in this plant appears to involve: (1) eccentric positioning of the nucleus within the sperm cell, (2) separation of cytoplasmic and nuclear portions of the sperm cell, and (3) fusion of the nuclear portion with the egg cell. This represents a previously undescribed mechanism by which male cytoplasmic organelles are eliminated from sperm cells prior to fusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322625
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  • 4
    Electronic Resource
    Electronic Resource
    Crystallization of the RNA-binding domain of the transcriptional antiterminator protein sacy from Bacillus subtilis (1997)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 28 (1997), S. 590-594 
    Details
    ISSN: 0887-3585
    Keywords: SacY ; antiterminator ; RNA-binding motif ; crystallization ; x-ray crystallography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: SacY is the antiterminator protein involved in the induction by sucrose of the expression of the levansucrase gene (sacB) of Bacillus subtilis. In the presence of sucrose, SacY is activated and prevents premature termination of transcription by binding to a RNA-antiterminator (RAT) sequence partially overlapping with the terminator sequence. SacY consists of a RNA-binding N-terminal domain, SacY(1-55), and a regulatory domain, SacY(56-280), sensitive to the sucrose concentration. SacY(1-55) is in itself capable of binding to the RAT sequence and preventing termination independently of the sucrose concentration. In this paper we describe the overexpression, the purification, and the crystallization of SacY(1-55). We obtained six different crystal forms, some of them diffracting to high resolution (〉1.5 Å). Self rotation function calculations indicated the presence of a dimer in the asymmetric unit, which is in agreement with a proposed oligomeric state in solution as observed by high-resolution NMR measurements. The crystallization of some site-directed cysteine mutants opens the way of solving the structure by multiple isomorphous replacement. Proteins 28:590-594, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Purification, crystallization, and preliminary X-ray analysis of PepX, an X-prolyl dipeptidyl aminopeptidase from Lactococcus lactis (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 278-281 
    Details
    ISSN: 0887-3585
    Keywords: overproduction ; crystallography ; X-prolyl dipeptidyl aminopeptidase ; PepX ; Lactococcus lactis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The X-prolyl dipeptidyl aminopeptidase PepX, a serine peptidase isolated originally from Lactococcus lactis subsp lactis NCDO 763, was cloned and overproduced in Escherichia coli. The enzyme was isolated in its active form in two purification steps. Crystals of PepX were grown by the hanging drop vapor diffusion method using polyethyleneglycol 4000 as precipitant at pH 5.0. The crystals are orthorhombic with cell dimensions a = 92.8 Å, b = 102.6 Å, and c = 101.6 Å, space group P21212, and probably contain one monomer of 87.5 kDa in the asymmetric unit. The crystals, very stable under X-rays, diffract to at least 2.2 Å and are suitable for high-resolution structural analysis. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340230216
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  • 6
    Electronic Resource
    Electronic Resource
    Micro-isoelectric focusing of single pollen grains from Cucurbita pepo L (1986)
    Weinheim : Wiley-Blackwell
    Electrophoresis 7 (1986), S. 148-149 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A technique of isoelectric focusing of proteins from single pollen grains has been developed using ultrathin polyacrylamide gels. On a single gel, one hundred grains may be compared for total proteins or enzyme patterns. With this technique it was possible to reveal heterogeneity of pollen grains in a population at a genetic level and in relation to pollen viability.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150070309
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  • 7
    Electronic Resource
    Electronic Resource
    Use of a fast protein electrophoretic purification procedure for N-terminal sequence analysis to identify S-locus related proteins in stigmas of Brassica oleracea (1991)
    Weinheim : Wiley-Blackwell
    Electrophoresis 12 (1991), S. 646-653 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: In the cruciferous plant Brassica oleracea L. (cabbage), the S-locus specific glycoproteins (SLSGs) isolated only in stigmas are considered to play an important role in the normal prevention of self-fertilization. Recent molecular data have shown that the gene encoding these glycoproteins (the SLG gene) belonged to a multigenic family consisting of about 10 homologous copies among which an, other member is expressed, the S-locus related gene (SLR1gene). Our aim was to determine whether the SLR1-gene proteins were expressed in the stigmatic tissues. We first identified the putative SLSGs or SLR1-proteins by Con A-peroxidase detection of glycoproteins separated after isoelectric focusing in polyacrylamide gels. We describe a fast purification procedure for the glycoproteins of interest, based on analytical isoelectric focusing, electrophoresis, and electroblotting of proteins onto polyvinylidene difluoride membranes. Blotted proteins were sequenced for N-terminal amino acid determination. By comparison of the N-terminal sequences of the purified proteins with the peptide sequence predicted from the SLR1-cDNA, we demonstrate the expression of SLR1-like proteins in stigmas of B. oleracea.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150120909
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