Anthoceros-Nostoc Symbiosis: Immunoelectronmicroscopic Localization of Nitrogenase, Glutamine Synthetase, Phycoerythrin and Ribulose-1,5-bisphosphate Carboxylase/Oxygenase in the Cyanobiont and the Cultured (Free-living) Isolate Nostoc 7801

N., A.; Borthakur, M.; Singh, Surendra; Bergman, Birgitta

doi:10.1099/00221287-135-2-385

Cited by 18 publications

(38 citation statements)

References 17 publications

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“…In heterocystous cyanobacteria occurring as symbionts, nitrogenase has been shown to be exclusively located in heterocysts (see Bergman, Lindblad & Rai, 1986;Braun-Howland et al, 1988;Rai et al, 1989;Soderback, Lindblad & Bergman, 1990). The L. confinis cyanobiont is one such cyanobacterium and our results showing the presence of nitrogenase in heterocysts (Fig.…”

Section: Discussionsupporting

confidence: 67%

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

1993

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SUMMARYThallus ultrastructure and the localization of proteins involved in photosynthesis, N^ fixation and animonia assimilation was studied in the Lichina confinis (O. F. Mull) C. Ag.-Calothrix symbiosis. The lichen thallus showed profuse branching. Within this, the cyanobiont was located in the cortical zone. Haustoria were frequently observed in contact with vegetative cells of the cyanobiont but not with heterocysts. An extensive mucilage layer containing numerous vesicles occurred around cyanobiont cells. Immunolabelling showed nitrogenase to be exclusively located in heterocysts of the cyanobiont and the free-living Calothrix sp. Glutamine synthetase (GS) levels in the cyanobiont were found to be drastically decreased compared to the levels in free-living (cultured) Calothrix sp. Such a decrease was more prominent in mature parts of the thallus than in the apical region. Rubisco was mostly located in carboxysomes of the vegetative cells of the cyanobiont. There were relatively low levels of Rubisco in tbe cytoplasm of vegetative cells, wbile heterocysts sbowed negligible levels. In free-living (cultured) Calothrix sp., pbycoerytbrin (PE) was found to be located along tbe tbylakoid membranes both in vegetative cells and beterocysts. Cyanobiont cells sbowed a similar pattern but tbe levels were relatively lower.

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Section: Discussionsupporting

confidence: 67%

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

1993

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“…First, the nitrogenase label in Symploca was confined to a small percentage of the cells (9 %). The label intensity in these Symploca cells was high and in intensity comparable to those detected, using the same antibody (against dinitrogenase reductase) and embedding procedures, in heterocystous (BraunHowland et al, 1988 ;Rai et al, 1989 ;So$ derba$ ck, Lindblad & Bergman, 1990 ;Janson, Rai & Bergman, 1993) and other non-heterocystous (Stal & Bergman, 1990 ;Bergman & Carpenter, 1991 ;Rai, Borthakur & Bergman, 1992 ;Fredriksson & Bergman, 1995) cyanobacteria. The low proportion of nitrogenasecontaining cells must therefore be responsible for the nitrogenase activity measured.…”

Section: mentioning

confidence: 72%

Aerobic nitrogen fixation is confined to a subset of cells in the non‐heterocystous cyanobacterium Symploca PCC 8002

et al. 1998

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Symploca PCC 8002 Ku$ tzing is a filamentous cyanobacterium that lacks the specialized cells, known as heterocysts, that protect nitrogenase from O # in most aerobic N # -fixing cyanobacteria. Nevertheless, Symploca is able to carry out N # fixation in the light under aerobic conditions. When cultures were grown under light\dark cycles, nitrogenase activity commenced and increased in the light phase and declined towards zero in the dark. Immunolocalization of dinitrogenase reductase in sectioned Symploca trichomes showed that the enzyme was present only in 9 % of the cells. These cells lacked any obvious mechanical protection against atmospheric O # and their ultrastructural characteristics were similar to those of cells that did not contain any dinitrogenase reductase. The nitrogenase-containing cells possessed carboxysomes that were rich in ribulose-1,5-bisphosphate carboxylase\oxygenase and phycoerythrin, a light harvesting pigment of PS II. This indicates that these cells had a capacity for both N # fixation and photosynthesis. The significance of the localization pattern for dinitrogenase reductase is discussed in the context of N # fixation in Symploca PCC 8002.

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“…While there is no significant difference in the overall concentration of GS protein, the in vitro GS catalytic activity of symbiotic Nostoc is only 15% that of free-living cultures (86). Immunoelectronmicroscopic analyses indicated that the accumulation of GS protein in the heterocysts of symbiotic Nostoc in the Anthoceros association was lower than that in the heterocysts in the freeliving growth state and equal to that in the heterocysts in vegetative cells (150). In summary, the symbiotic state with Anthoceros may lead to small differences in the level of GS protein but large differences in activity, perhaps the result of modification of the enzyme.…”

Section: Physiological Characteristics Of Cyanobacteria In the Symbiomentioning

confidence: 99%

Regulation of Cellular Differentiation in Filamentous Cyanobacteria in Free-Living and Plant-Associated Symbiotic Growth States

Meeks

Elhai

2002

Microbiol Mol Biol Rev

365

361

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Certain filamentous nitrogen-fixing cyanobacteria generate signals that direct their own multicellular development. They also respond to signals from plants that initiate or modulate differentiation, leading to the establishment of a symbiotic association. An objective of this review is to describe the mechanisms by which free-living cyanobacteria regulate their development and then to consider how plants may exploit cyanobacterial physiology to achieve stable symbioses. Cyanobacteria that are capable of forming plant symbioses can differentiate into motile filaments called hormogonia and into specialized nitrogen-fixing cells called heterocysts. Plant signals exert both positive and negative regulatory control on hormogonium differentiation. Heterocyst differentiation is a highly regulated process, resulting in a regularly spaced pattern of heterocysts in the filament. The evidence is most consistent with the pattern arising in two stages. First, nitrogen limitation triggers a nonrandomly spaced cluster of cells (perhaps at a critical stage of their cell cycle) to initiate differentiation. Interactions between an inhibitory peptide exported by the differentiating cells and an activator protein within them causes one cell within each cluster to fully differentiate, yielding a single mature heterocyst. In symbiosis with plants, heterocyst frequencies are increased 3- to 10-fold because, we propose, either differentation is initiated at an increased number of sites or resolution of differentiating clusters is incomplete. The physiology of symbiotically associated cyanobacteria raises the prospect that heterocyst differentiation proceeds independently of the nitrogen status of a cell and depends instead on signals produced by the plant partner

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Anthoceros-Nostoc Symbiosis: Immunoelectronmicroscopic Localization of Nitrogenase, Glutamine Synthetase, Phycoerythrin and Ribulose-1,5-bisphosphate Carboxylase/Oxygenase in the Cyanobiont and the Cultured (Free-living) Isolate Nostoc 7801

Cited by 18 publications

References 17 publications

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

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

Aerobic nitrogen fixation is confined to a subset of cells in the non‐heterocystous cyanobacterium Symploca PCC 8002

Regulation of Cellular Differentiation in Filamentous Cyanobacteria in Free-Living and Plant-Associated Symbiotic Growth States

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