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  • 1
    Electronic Resource
    Electronic Resource
    Adenosine 5'-diphosphate binding and the active site of nucleoside diphosphate kinase (1994)
    s.l. : American Chemical Society
    Biochemistry 33 (1994), S. 459-467 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00168a010
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  • 2
    Electronic Resource
    Electronic Resource
    Lipochemistry of the progamic stage of a self-incompatible species: Neutral lipids and fatty acids of the secretory stigma during its glandular activity, and of the solid style, the ovary and the anther in Forsythia intermedia Zab. (Heterostylic species) (1977)
    Springer
    Planta 137 (1977), S. 177-184 
    Details
    ISSN: 1432-2048
    Keywords: Forsythia ; Heterostyly ; Lipids ; Reproduction, sexual
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chromatographic (thin-layer, gas column, column chromatography) analyses of neutral lipids and fatty acids of reproductive tissues of Forsythia intermedia Zab., a self-incompatible species, were performed with two objectives in mind: 1. To determine whether there is a qualitative evolution of the different classes of lipids and fatty acids that could be correlated with the three functional stages observed during previous histochemical and ultrastructural studies. The stigmatic exudate and intracellular accumulations consist mainly of neutral lipids. 2. To compare the lipid composition of the stigma (both “thrum” and “pin” forms) with that of the style, the ovary, and the anther, and to investigate the possible existence of a stigma-specific lipid compound. Stigmatic neutral lipids are found mostly in a glyceridic mixture probably containing hydrocarbons and terpenes. The fatty acids identified are between C:7 and C: 12, with the maximum unsaturated form being a C: 18. During the secretory process there is no great qualitative diference between the neutral lipids and fatty acids found in the stigmas of “thrum” and “pin” forms. Sterols are present in styles, ovaries, and anthers, but not in stigmas. They represent the only difference in the lipid composition of these various floral structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387556
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  • 3
    Electronic Resource
    Electronic Resource
    In-vitro culture of fertilized embryo sacs of maize: Zygotes and two-celled proembryos can develop into plants (1993)
    Springer
    Planta 189 (1993), S. 213-217 
    Details
    ISSN: 1432-2048
    Keywords: Embryo sac (fertilized) ; Plant regeneration (direct) ; Zea ; Zygote ; Zygotic embryo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fertilized embryo sacs of Zea mays L. surrounded by a few layers of nucellar cells were cultured in vitro. Primary expiants contained zygotes or twocelled proembryos. Embryos of various sizes and shapes were isolated from 12–48% of explants after two weeks of culture in hormone-free media supplemented with 6–12% of sucrose. Many embryos were at the transition or proembryo stages whilst the rest were either differentiated, with a scutellum, a coleoptile and a shoot apex, or had a deformed apical part. Organogenesis started in 36–89% of embryos cultured on a semisolid medium supplemented with coconut water. Most of the embryos formed only roots but up to 9% of embryos regenerated into plants. This simple method leads the way to plant regeneration from in-vitro-manipulated zygotes or proembryos of maize.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195079
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  • 4
    Electronic Resource
    Electronic Resource
    Nuclear DNA amounts in the egg and zygote of maize (Zea Mays L.) (1995)
    Springer
    Planta 197 (1995), S. 641-645 
    Details
    ISSN: 1432-2048
    Keywords: Fertilization (in vivo) ; Karyogamy ; Zea embryogenesis ; Zygotic DNA synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nuclear DNA content of isolated eggs and zygotes of maize was estimated using 4′,6-diamidino-2-phenylindole (DAPI) staining and microspectrofluorometry. The data indicate that egg nuclei contain the 1C level of DNA (basic haploid amount) at the time of karyogamy, and that, by inference, the sperm nuclei are also at 1C. Fertilization occurred in most ovules by 24–28 h post-pollination (hpp), and DNA synthesis was well underway by 27–31 hpp. By 30–34 hpp, 80% of the zygotes were at the 3C DNA level or above, and many were undergoing mitosis. This study provides information that is pertinent to experiments on the microinjection of exogenous DNA into isolated zygotes of maize, and it will serve as a comparative base for future determinations of the DNA content of zygotes produced and cultured in vitro.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191572
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Viability of Cururbita pepo pollen: biophysical and structural data (1989)
    Springer
    Planta 179 (1989), S. 165-170 
    Details
    ISSN: 1432-2048
    Keywords: Cucurbita pollen ; Dehydration (pollen) ; Plasma membrane ; Pollen (viability, water) ; Pollen wall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During ageing of the short-lived pollen grains of Cucurbita pepo L., water loss was examined in relation to viability using biophysical (1H-nuclear magnetic resonance, NMR) and cytological methods (fluorochromatic reaction test, freezefracture and scanning electron microscopy). A semi-logarithmic representation of the pollen weight loss demonstrated the complexity of the dehydration process. A the study of proton loss using 1H-NMR indicated that two major releases water of had taken place, each with different flux rates. Pulse 1H-NMR experiments showed the occurrene of non-exponential signal decay as a function of time, indicating the existence of different fractions of water in a pollen grain sample. These fractions leave the pollen grain at different times during pollen dehydration, and one of them (that of the so-called “vital water”) can be related to pollen viability. The quantity of protons giving a signal during pulse 1H-NMR experiments was very low when the pollen grains were judged to be dead according to the fluorochromatic test. Freeze-fracture replicas of these dead pollen grains (less than 25% water content) showed that the plasma membrane had become detached from the intine surface; this ultrastructural feature might therefore be involved in the loss of pollen viability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393686
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  • 7
    Electronic Resource
    Electronic Resource
    S-locus glycoproteins are expressed along the path of pollen tubes in Brassica pistils (1995)
    Springer
    Planta 196 (1995), S. 614-621 
    Details
    ISSN: 1432-2048
    Keywords: Brassica ; Pistil specific gene ; Pollination ; Self-incompatibility ; S-locus glycoproteins ; Transmitting tissue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Brassica, self-incompatibility has been correlated with S-locus glycoproteins (SLG) localized at the site of pollen rejection, the stigmatic papillae. In this paper we present immunocytochemical evidence that during development of the pistil SLG proteins accumulate not only in the stigmatic papillae, but also in the transmitting tissue of stigma, style and ovary, along the pathway followed by the pollen tube. This observation was confirmed by the biochemical characterization of stylar and ovarian SLG proteins and by the detection of SLG transcripts in style/ovary tissues by polymerase chain reaction analysis. Thus we demonstrate similarities between the pattern of SLG gene expression in Brassica (sporophytic self-incompatibility system) and that of S products in Nicotiana (gametophytic self-incompatibility system) which may reflect relationships between the self-incompatibility systems. An active role of SLG gene products during the pollen-tube growth in the pistil is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203663
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  • 8
    Electronic Resource
    Electronic Resource
    Late steps of egg cell differentiation are accelerated by pollination in Zea mays L. (2000)
    Springer
    Planta 210 (2000), S. 749-757 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Egg cell (differentiation) – Embryo sac (maturity) – Female receptivity – Pollination signal –Zea (egg cells)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract.  Egg cells were analysed cytologically during the female receptivity period in maize (Zea mays L., line A 188). Three classes of egg cell were distinguished: type A – small, non-vacuolated cells with a central nucleus; type B – larger cells with small vacuoles surrounding the perinuclear cytoplasm located in the middle of the cell; type C – big cells with a large apical vacuole and the mid-basal perinuclear cytoplasm. The less-dense cytoplasm of the vacuolated egg cells usually contained numerous cup- or bell-shaped mitochondria. The three egg types appear to correspond to three late stages of egg cell differentiation. The frequencies of each of the three egg types were monitored in developing maize ears before and after pollination. In young ears, with the silks just extending out of the husks, small A-type cells were found in about 86% of ovules. Their frequency decreased to about 58% at the optimum silk length, remained unchanged in non-pollinated ears, and fell to 16% at the end of the female receptivity period. However, after pollination and before fertilisation the frequency of these cells decreased to about 33%, and the larger vacuolated egg cells (types B and C) prevailed. At various stages of the receptivity period, pollination accelerated changes in the egg population, increasing the number of ovules bearing larger, vacuolated egg cells. Experiments with silk removal demonstrated that putative pollination signals act immediately after pollen deposition and are not species-specific.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050676
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  • 9
    Electronic Resource
    Electronic Resource
    Novel phenotypes and developmental arrest in early embryo specific mutants of maize (1999)
    Springer
    Planta 210 (1999), S. 1-8 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Embryo development ; Embryo specific mutants ; Mutant (maize ; emb) ; Mutator tagging ; Zea mays (mutants)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Embryo specific (emb) mutants exhibit aberrant embryo development without deleterious effects on endosperm development. We have analyzed five emb mutants of maize, which, based on their developmental profiles can be divided into two groups: mutants arrested at early stages and mutants with novel phenotypes. The members of the first group resemble wild-type proembryos and never reach other developmental stages. In the second group the tube-shaped mutants emb*-8522 and emb*-8535 completely lack apical-basal differentiation, while in mutant emb*-8516 a second embryo-like structure arises from the suspensor. The five emb mutations analyzed are non-allelic and two of the mutations are very likely caused by insertion of the transposon mutator, opening the door for their molecular analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050647
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  • 10
    Electronic Resource
    Electronic Resource
    Expression, purification, crystallization and preliminary X-ray analysis of the cathelicidin motif of the protegrin-3 precursor (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 1677-1679 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Numerous precursors of antibacterial peptides with unrelated sequences share a similar prosequence which belongs to the cathelicidin family of proteins. The three-dimensional structure of this cathelicidin motif, which contains two disulfide bonds, has not yet been reported. The cathelicidin motif (ProS) of the protegrin-3 precursor was overexpressed in Escherichia coli as a His-tagged protein. The His6 tag was removed by thrombin cleavage. ProS was purified to homogeneity and single crystals were obtained by the hanging-drop vapour-diffusion method at pH 3–4. Preliminary X-ray diffraction analysis indicated that these crystals belong to the hexagonal space group P6122 or P6522, with unit-cell parameters a = b = 51.42, c = 134.25 Å. These crystals diffracted beyond 2.75 Å (1.9 Å at ESRF) and contain one molecule per asymmetric unit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444901012598
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