THE <i>AZOLLA‐ANABAENA AZOLLAE</i> RELATIONSHIP

Peters, Gerald A.; Toia, Robert E.; Raveed, Dan; Levine, N. J.

doi:10.1111/j.1469-8137.1978.tb01591.x

Cited by 63 publications

(27 citation statements)

References 20 publications

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“…As leaf development proceeds, filaments of the symbiont colonize cavities formed in the aerial dorsal leaf lobe. In conjunction with this, multicellular hairs, some of which have transfer cell characteristics, are differentiated from host cells during cavity formation (5,22) and the symbiont exhibits a decreased cell division along with cell enlargement and a large increase in heterocyst frequency (10). The latter is paralleled by an increase in C2H2 reduction capacity of the individual leaf lobes (11).…”

Section: Acetylene Reduction Assays-nitrogenasementioning

confidence: 95%

“…The latter is paralleled by an increase in C2H2 reduction capacity of the individual leaf lobes (11). Due to the developmental pattern of this association (11,22) the values for enzyme activities as well as Chl and protein attributed to the host and symbiont necessarily represent an average of their respective total contributions. Although the enzymes of ammonia assimilation are present in the heterogeneous population of the isolated symbiont, they may be localized in algal filaments found in specific developmental stages of the association.…”

Section: Acetylene Reduction Assays-nitrogenasementioning

confidence: 99%

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Azolla-Anabaena Relationships

Ray

Peters²,

Toia³

et al. 1978

Plant Physiol.

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The N2-fixing Azolla-Anabaena symbiotic association is characterized in regard to individual host and symbiont contributions to its total chlorophyll, protein, and levels of ammonia-assimilating enzymes. The phycocyanin content of the association and the isolated blue-green algal symbiont was used as a standard for this characterization. Phycocyanin was measured by absorption and fluorescence emission spectroscopy. The phycocyanin content and total phycobilin complement of the symbiotic algae were distinct from those of Anabaena cylindrica and a free-living isolate of the Azoila endophyte. The algal symbiont accounted for less than 20% of the association's chlorophyll and protein. Acetylene reduction rates in the association (based solely on the amount of algal chlorophyll) were 30 to 50% higher than those attained when the symbiont was isolated directly from the fern. More than 75% of the association's glutamate dehydrogenase and glutamine synthetase activities are contributed by the host plant. The specific activity of glutamate dehydrogenase is greater than that of glutamine synthetase in the association and individual partners. Both the host and symbiont have glutamate synthase activity. The net distribution of these enzymes is discussed in regard to the probable roles of the host and symbiont in the assimilation of ammonia resulting from N2 fixation by the symbiont.The Azolla-Anabaena azollae symbiosis is an N2-fixing association between a eukaryotic fern and a prokaryotic alga, both of which exhibit a higher plant type of photosynthesis (18,19).As an approach toward the characterization of the role of the host and symbiont4 in the association, it was considered important to determine the contribution of the partners to the association's Chl, protein, and ammonia-assimilating enzymes. While the alga could be isolated free of the fern, its removal from the host was never complete. Thus it was necessary to find an independent quantitative estimate for the amount of alga in the association. While nitrogenase is unique to the alga (21) its lability makes it unsuitable for quantitation. Chl a/b ratios provided another estimate, but this was based on the absence of Chl b from the alga (20) and was therefore not as sensitive. A third method, the quantitation of phycobilins which are unique to the alga in the association, was employed. A procedure involving fluorescence emission spectroscopy at 77 K permitted quantitative measurement of phycobilins in the association, where the fern's Chl b '

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Section: Acetylene Reduction Assays-nitrogenasementioning

confidence: 95%

Section: Acetylene Reduction Assays-nitrogenasementioning

confidence: 99%

Azolla-Anabaena Relationships

Ray

Peters²,

Toia³

et al. 1978

Plant Physiol.

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“…A feature that may be common to all symbiotic cavities is the presence of mucilage, a complex polysaccharide (133,143,155,157,168,196). The cavities are also relatively axenic, except for the cyanobacterium itself (84).…”

Section: What Do Plants Bring To the Symbiosis?mentioning

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

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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“…The Anabaena occupies a specific cavity in the leaf of the AzoZZa and forms close association with the host cells [3]. The molecular mechanisms, leading to the recognition and association between the two cell types, have not been yet clarified.…”

Section: Introductionmentioning

confidence: 99%