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  • 1
    Electronic Resource
    Electronic Resource
    Glutamine synthetase: activity and localization in cyanobacteria of the cycadsCycas revoluta andZamia skinneri (1986)
    Springer
    Planta 169 (1986), S. 1-7 
    Details
    ISSN: 1432-2048
    Keywords: Cyanobacterium ; Cycad ; cyanobacterium symbiosis ; Cycas ; Glutamine synthetase ; Symbiosis ; Zamia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen-fixing cyanobacteria inhabit the zone between the inner and outer cortex of cycad coralloid roots. In the growing tip of such roots the cyanobacterial heterocyst frequency, nitrogenase activity (C2H2-reduction) and glutamine synthetase activity (both transferase and biosynthetic) were comparable to those found in freeliving cyanobacteria. The relative level of glutamine synthetase protein and its pattern of cellular/subcellular localization in heterocysts and vegetative cells were also similar to those of free-living cyanobacteria. However, there was a progressive decline in nitrogenase activity along the coralloid root with maximum reduction occurring in the regions farthest from the growing tip. A similar but less pronounced pattern was observed for glutamine synthetase activity. Distribution of glutamine synthetase protein in cyanobacteria in the first 2–3 mm of the root tip indicated a slight decrease in the heterocysts and vegetative cells. However, the overall level of cyanobacterial glutamine synthetase protein did not change because of a drastic increase in the numbers of heterocysts, which contain a proportionally higher level of glutamine synthetase than the vegetative cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01369768
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  • 2
    Electronic Resource
    Electronic Resource
    Absence of the glutamine-synthetase-linked methylammonium (ammonium)-transport system in the cyanobiont of Cycas-cyanobacterial symbiosis (1986)
    Springer
    Planta 169 (1986), S. 379-381 
    Details
    ISSN: 1432-2048
    Keywords: Ammonium transport ; Anabaena ; Cycad-cyanobacterium symbiosis ; Cyanobacterium ; Cycas ; Methylammonium transport ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using the ammonium analogue 14CH3NH 3 + , ammonium transport was studied in the cyanobiont cells freshly isolated from the root nodules of Cycas revoluta. An L-methionine-dl-sulphoximine (MSX)-insensitive ammonium-transport system, which was dependent on membrane potential (ΔΨ), was found in the cyanobiont. However, the cyanobiont was incapable of metabolizing exogenous 14CH3NH 3 + or NH 4 + because of the absence of another ammonium-transport system responsible for the uptake of ammonium for assimilation via glutamine synthetase (EC 6.3.1.2). Such a modification seems to be the result of symbiosis because the free-living cultured isolate, Anabaena cycadeae, has been shown to possess both the ammonium-transport systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392134
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    Paper (German National Licenses)
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