Dinitrogenase reductase (Fe-protein) of nitrogenase in the cyanobacterial symbionts of three Azolla species: Localization and sequence of appearance during heterocyst differentiation

Abstract

Transmission electron microscopy and immunocytological labeling were used to study the distribution and ontological occurrence of dinitrogenase reductase (Fe-protein) of nitrogenase in cyanobacterial symbionts within young leaves of the water-ferns Azolla filiculoides Lamarck, A. caroliniana Willdenow, and A. pinnata R. Brown. Rabbit anti-dinitrogenase reductase antisera and goat anti-rabbit-immunoglobulin G antibody conjugated to colloidal gold were used as probes. Western blot analyses showed that a polypeptide of approx. 36 kDa (kdalton) was recognized in the symbionts of all three Azolla species and that the polyclonal sera used were monospecific. In all symbionts, nitrogenase was immunologically recognizable within heterocysts. It was absent from vegetative cells, and also from the akinetes of the A. caroliniana and A. pinnata symbionts. The differentiation of vegetative cells into heterocysts in all three symbionts was initiated by formation of additional external cell-wall layers and narrowing of the neck followed by loss of glycogen, mild vesiculation of thylakoid membranes, and the appearance of polar nodules. No nitrogenase was detected at these early stages, but it appeared in the intermediate proheterocyst stage concomitantly with the formation of contorted membranes, and reached the strongest labeling in mature heterocysts, containing extensive tightly packed membranes. Nitrogenase was evenly distributed throughout heterocysts except at the polar regions, which contained honey-comb configurations and large polar nodules. With increased age of the A. caroliniana and A. pinnata symbionts, heterocysts became highly vesiculated, with a concomitant decrease in the amount of nitrogenase detected.

The marine lichen Lichina confinis (O. F. Müll.) C. Ag.: ultrastructure and localization of nitrogenase, glutamine synthetase, phycoerythrin and ribulose 1, 5‐bisphosphate carboxylase/oxygenase in the cyanobiont

“…We tested these antibodies against Calothrix sp. extracts using western blotting (Braun-Howland et al, 1988). The results were identical to those obtained by , showing single bands of 36, 50 and 53 kDa relative molecular mass (M^) for nitrogenase Fe-protein, GS and Rubisco, respectively, and two bands of 20 and 24 kDa M, for PE (data not shown).…”

Superoxide Dismutase in the Symbiont Anabaena azollae Strasb.

“…Vegetative cell and heterocyst ultrastructure was very similar to that of symbiont A. filiculoides (5) or free-living A.…”

Occurrence and Localization of Phycoerythrin in Symbiotic Nostoc of Cycas revoluta and in the Free-Living Isolated Nostoc 7422

“…Free-living Nostoc 7422 (PCC 7422, ATCC 29132), originally isolated from the cycad Cycas sp., was obtained from the Pasteur Culture Collection (Paris, France). Cells were grown and harvested as described earlier (16 (6) except that the nitrocellulose-membranes were incubated with primary antiserum against C-phycoerythrin purified from the cyanobacterium Phormidium persicinum (rabbit anti-C-phyroerythrin antiserum, 1:500 dilution) (8).…”

“…In filamentous heterocystous cyanobacteria differentiation of a vegetative cell to a heterocyst leads to pronounced rearrangement of the thylakoid membranes as well as a high protease activity (6,9). Atmospheric N2 is fixed by the enzyme complex nitrogenase, cellularly localized to heterocysts only (5,6,23).…”

“…Atmospheric N2 is fixed by the enzyme complex nitrogenase, cellularly localized to heterocysts only (5,6,23). The differentiation process leads to a drastic decrease and/or loss ofthe phycobiliprotein from the heterocysts of some cyanobacteria (9,24).…”