Organellen-Reduplikation und Zellkompartimentierung

Schnepf, E.

doi:10.1007/978-3-642-47409-5_18

Cited by 34 publications

(5 citation statements)

References 48 publications

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“…are endosymbionts of non‐green unicellular organisms ( Paramecium bursaria ) (Karakashian 1975; Smith & Douglas 1987; Reisser 1992). Actually, all eukaryotic cells can be regarded as holobionts because the endosymbiont theory considers the organelles mitochondria and chloroplasts as being original endosymbionts in evolution of the eukaryotic cells (Schimper 1883; Mereschkowski 1905; Schnepf 1966; Sagan 1967; Keeling & Archibald 2008; Nowack et al. 2008).…”

Section: Holobiont Emergence: Unitary Levels Of Organismic Integrationmentioning

confidence: 99%

Modularity and emergence: biology’s challenge in understanding life

Lüttge

2012

Plant Biology

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This essay juxtaposes modularity and emergence in the consideration of biological systems at various scalar levels of spatio-temporal organisation. It is noted that reductionism, specialisation and modularity are basic prerequisites for understanding life. It is realised that increased progress of scientific biology in elucidating mechanisms at the level of modular components supports the accusation that the more it advances in materialistic description of details, the more it diverts from understanding the innate properties of life. It is clear that modularity, by taking the whole as the sum of its parts, is insufficient for understanding living systems. At the same time, however, there is emergence, as advocated by Robert Laughlin. Emergence after the integration of modules leads to completely new properties of individual organisms as unique unitary entities, and also of systems of organisms with synergistic and antagonistic interactions of the integrated species. The discussion is predominantly based on examples from plant biology. At hierarchically higher scalar levels emergent biological systems are networks integrating species, biotopes, ecosystems and the entire biosphere of Earth, also named Gaia by James Lovelock, in a natural scientific respect. While investigating modules remains essential, biology as a nature science needs to merge and integrate such information to be able to unfold emergence. Through efforts towards visualising and understanding emergent diversity and complexity, the research discipline of biology will provide invaluable contributions to understanding life, and thus refute the accusation that it diverts from embracing the innate properties of life.

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Section: Holobiont Emergence: Unitary Levels Of Organismic Integrationmentioning

confidence: 99%

Modularity and emergence: biology’s challenge in understanding life

Lüttge

2012

Plant Biology

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“…Life depends on homeostatic mechanisms that maintain a favourable and within limits a rather constant chemical environment in the cell. According to the eukaryotic cell theorem of Schnepf (1966), each membrane separates a plasmatic from an extraplasmatic compartment, the latter usually characterized by less negative (i.e. more oxidizing) redox potentials, while the plasmatic compartments are characterized by properties such as presence of nucleic acids, nmolar Ca 2+ activity, neutral pH and precise redox buffering in a narrow range.…”

Section: Introductionmentioning

confidence: 99%

Redox signal integration: from stimulus to networks and genes

Dietz

2008

Physiologia Plantarum

163

121

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Recent research has established redox-dependent thiol modification of proteins as a major regulatory layer superimposed on most cell functional categories in plants. Modern proteomics and forward as well as reverse genetics approaches have enabled the identification of a high number of novel targets of redox regulation. Redox-controlled processes range from metabolism to transport, transcription and translation. Gene activity regulation by transcription factors such as TGA, Athb-9 and RAP2 directly or indirectly is controlled by the redox state. Knowledge on putative redox sensors such as the peroxiredoxins, on redox transmitters including thioredoxins and glutaredoxins and biochemical mechanisms of their linkage to the metabolic redox environment has emerged as the framework of a functional redox regulatory network. Its basic principle is similar in eukaryotic cells and particularly complex in the photosynthesizing chloroplast. Methods and knowledge are now at hand to develop a quantitative understanding of redox signalling and the redox regulatory network in the eukaryotic cell.

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“…Instead it has become increasingly clear that among some of the states termed "syncyanoses" (pascher, 1914, 1929) formerly interpreted as associations of endosymbiotic blue-green bacteria (cyanelles) with eukaryotic hosts there are several in which the pigmented bodies are so intermediate in appearance that it is entirely an arbitrary decision at present as to whether they are bluegreen cells or chloroplasts whereas others are clearly blue-greens. This is particularly the case for the bodies within the cryptomonad Cyanophora paradoxa and the coccoid alga of uncertain affinities (possibly Chlorophycean), Glaucocystis nostochinearum (see reviews by Taylor, 1970;Margulis, 1970, andSchnepf &Brown, 1971). Stanier (1970) has indicated how the criteria for the determination of cyanelles from chloroplasts, proposed by Pringsheim (1958) andGeitler (1959), are inadequate for the task of dealing with the latter two species.…”

Section: Discussionmentioning

confidence: 99%

“…In this sense the protomitochondrion and protochloroplast have never truly entered the host cell, but are instead "embraced" by it, a situation which has remained unchanged over the ages even though the membranes surrounding them have become specialised for their tasks of transport and control. Schnepf (1966) approached this aspect from a slightly different angle.…”

Section: Cell Topologymentioning

confidence: 99%

“…Even the distinction of prokaryotic cell, eukaryotic cell, eukaryotic multi-cellular organism, although an improvement, masks the dyad/triad distinction and their "multicellular" products. Schnepf (1966) has proposed the terms protocyte and eucyte for the equivalents of monads and dyads, but he did not take the concept further. His protocyte referred specifically to the protomitochondrion.…”

Section: Fig I a Diagrammatic Representation Of The Consequences Ofmentioning

confidence: 99%

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Ii. Implications and Extensions of the Serial Endosymbiosis Theory of the Origin of Eukaryotes

Taylor

1974

TAXON

183

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Summary In comparison to other theories put forward so far, the Serial Endosymbiosis Theory appears to be the most critically favoured as an explanation for the origin of mitochondria and chloroplasts. For this reason some of its implications are drawn attention to. In particular it is shown that present hierarchical concepts and terminology based on the classical cell theory are inadequate to cope with the S.E.T. (as the theory is abbreviated here). It is shown that the topological relations of mitochondria and chloroplasts to the cell suggest that they are topologically “outside” it, “embraced” rather than lying truly within it. This position is consistent with the S.E.T. On the other hand microtubule‐organising‐centres are truly within the cell. An autogenous origin for the latter seems to be more likely than the endosymbiotic proposal of Margulis. In addition to the primary origin of organelles by the transformation of entire prokaryotic endosymbionts, the possibility of the maintenance of eukaryotic organelles produced by one cell, taken into another, is discussed. Examples of some recently discovered, unusual photosynthetic states in ciliates, brought about by temporary foreign chloroplast maintenance, and possibly degeneration of endosymbiotic photosynthetic flagellates, are discussed in this context. The existence of some contemporary examples of photosynthetic bodies which seem to be intermediate between endosymbiotic blue‐green algae and chloroplasts, suggests that some organelles may have had a more recent origin than the Precambrian Era, the process being a continuous one. Some of the difficulties inherent in alternative theories for the origin of eukaryotes are discussed. It is stressed that alternative proposals have not yet received intensive exposition and comparisons with the S.E.T. are thus difficult. Attempts to use single criteria (particularly biochemical) as phylogenetic “markers” should be made with due consideration of the S.E.T. Finally, it has bearing on the recognition of kingdoms, for it widens the already acknowledged chasm between prokaryotes and eukaryotes, intermediates between the two types of organisation being impossible (as stressed by Margulis).

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Organellen-Reduplikation und Zellkompartimentierung

Cited by 34 publications

References 48 publications

Modularity and emergence: biology’s challenge in understanding life

Modularity and emergence: biology’s challenge in understanding life

Redox signal integration: from stimulus to networks and genes

Ii. Implications and Extensions of the Serial Endosymbiosis Theory of the Origin of Eukaryotes

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