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
