| | 1 | Author
| Margarete Hoffmans-Hohn, W. Olfgang, M. Artin, Klaus Brinkm | Requires cookie* | | | Title
| Multiple Periodicities in the Circadian System of Unicellular Algae  | | | | Abstract
| Three periodicities in the circadian range are observed when m easuring circadian parameters of unicellular organisms in long running experim ents (m ore than 15 days). This is dem onstrated for different organisms (Chlamydomonas, Euglena, C hlorella) and different parameters (auto kinesis, extracellular pH, C 0 2-and 0 2-partial pressure). H aving excluded analytical and experimental artefacts {i.e. filter leakage and subpopulation effects), the m ultiple periodicities have to be interpreted in a physiological m odel. The three p eriod icities always exhibit two common features: The locations o f the side peaks are sym m etrical to the m iddle peak and their energy contribution is always the same. W e therefore favour the m odel o f m ultiplicative coupling between the circadian oscillator and a low frequency oscillator m odulating the am plitude o f the circadian rhythm. Since the low frequency rhythm is not correlated to any exogenously running periodicity o f the experim ental surroundings, it is considered as generated by an endogenous oscillator. This shows the existence o f different biological long tim e oscillators in one single cell and contradicts the so-called m aster-clock hypothesis stating that one cell has only one clock related oscillator. | | | |
Reference
| Z. Naturforsch. 39c, 791—8 (1984); received D ecem ber 5 1983/M arch 17 1984 | | | |
Published
| 1984 | | | |
Keywords
| Circadian Rhythm, pH-Rhythm, Chlamydomonas, Euglena, Chlorella | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0791.pdf | | | | Identifier
| ZNC-1984-39c-0791 | | | | Volume
| 39 | |
| 2 | Author
| I. Perewoska, C. Vernotte, M. Picaud, C. Astier | Requires cookie* | | | Title
| Mutations in the Subunit of Photosystem II and Resistance to the Phenol Type Herbicide Ioxynil in Synechocystis PCC 6714 and 6803 | | | | Abstract
| Several herbicides block the photosystem II electron transfer because they compete with QB, the second stable electron acceptor o f photosystem II for binding to the D, subunit. We have previously isolated a mutant o f Synechocystis 6714 in which Asn is replaced by Thr at position 266 o f D, (G. Ajlani, I. Meyer, C. Vernotte, and Astier, FEBS Lett. 246, 2 0 7 -2 1 0 (1989)) and presenting resistance to ioxynil but not to D C M U . In this report we present selection, from this mutant, o f a double mutant with an additional substitution at position 264 (Ser by Ala). The sensitivity o f this mutant toward several herbicides is given and compared to those o f the mutants having only one substitution at 266 and one substitution at 264. It was also compared to a mutant o f Chlamydomonas having the same substitutions. This allows us to discuss the interaction o f various herbicides with the D , protein and to compare the herbicide binding niches o f Chlamydomonas and Synechocystis. | | | |
Reference
| Z. Naturforsch. 47c, 580—5 (1992); received March 13 1992 | | | |
Published
| 1992 | | | |
Keywords
| Cyanobacteria, Chlamydomonas, Herbicide-Resistant M utants, Photosynthesis, Sequence Analysis | | | |
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| default:Reihe_C/47/ZNC-1992-47c-0580.pdf | | | | Identifier
| ZNC-1992-47c-0580 | | | | Volume
| 47 | |
| 3 | Author
| Alexander Pazur, Hugo Scheer | Requires cookie* | | | Title
| The Growth of Freshwater Green Algae in Weak Alternating Magnetic Fields of 7.8 Hz Frequency | | | | Abstract
| Liquid cultures o f Chlorella kessleri, Scenedesmus armatus and Chlamydomonas reinhardtii have been grown phototrophically in weak (0 .2 -2 G) alternating (7.8 Hz) magnetic fields. The data indicate, that the rate o f cell division is larger at 0.2 than at 2 G, viz. that the higher fields have inhibitory effects on cell division and that there is possibly an optimum at = 1 G. N o reli able effect is found on the pigment contents. | | | |
Reference
| Z. Naturforsch. 47c, 690—6 (1992); received April 13/July 7 1992 | | | |
Published
| 1992 | | | |
Keywords
| Earth M agnetic Field, Schumann Resonance, Chlorella, Scenedesmus, Chlamydomonas, Chlorophyll | | | |
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| default:Reihe_C/47/ZNC-1992-47c-0690.pdf | | | | Identifier
| ZNC-1992-47c-0690 | | | | Volume
| 47 | |
| 4 | Author
| E. B. Racht, A. Trebst | Requires cookie* | | | Title
| Hypothesis on the Control of D 1 Protein Turnover by Nuclear Coded Proteins in Chlamydomonas reinhardtii | | | | Abstract
| A hypothesis is presented on the events in the degradation of the D 1 protein of photosys tem II in the light. It proposes the existence of a nuclear encoded cleavage system that is turning over and which is m odulated by its phosphorylation state. A new experimental ap proach is presented in which the D 1 protein degradation under photoinhibitory light is tested in Chlam ydom onas reinhardtii grown under phosphate deficiency and pretreated with cyclo-heximide. Under these conditions the degradation of the D 1 protein is delayed whereas in C hlam y dom onas reinhardtii grown in full medium the D 1 protein is rapidly disappearing in high light upon addition o f chloramphenicol (CAP) or lincomycin for inhibiting the resynthesis of the D 1 protein . Cycloheximide (C H I) has little effect on photoinhibition in such control cells. In cells grown, however, for 20 h in phosphate deficiency -such that there is not yet loss of photosynthesis capacity -pretreatment with cycloheximide or canavanine in low light the degradation of the D 1 protein even in 6 h high light is prevented to an appreciable extent. Further addition of CAP or lincomycin has only a small effect. [14C]leucine incorporation was used to show that there is no resynthesis and that the presence of the D 1 protein is due to a delay of degradation. The results are interpreted to show that excess high light which converts the D 1 protein into a potentially, degradable m ode is not sufficient for degradation of the D 1 protein. A cleavage system is needed as well. It is postulated that under phosphate deficiency and pre treatment with CHI or canavanine a nuclear coded cleavage system for the D 1 protein is depleted, i.e. the cleavage system for the rapidly turning over D 1 is also turning over. It is shown that under phosphate deficiency an alkaline phosphatase activity in the chloro plast and the thylakoid membrane o f Chlam ydom onas reinhardtii is increased. It is proposed that the ratio of kinase/phosphatase converts an active, stable phosphorylated cleavage system into a labile unphosphorylated and turning over state. | | | |
Reference
| Z. Naturforsch. 49c, 439 (1994); received January 31/May 13 1994 | | | |
Published
| 1994 | | | |
Keywords
| Chlamydomonas, D 1 Protein, Photoinhibition, Photosystem II, Phosphate Deficiency | | | |
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| default:Reihe_C/49/ZNC-1994-49c-0439.pdf | | | | Identifier
| ZNC-1994-49c-0439 | | | | Volume
| 49 | |
| 5 | Author
| Susana Shochata, Noam Adira, Alma Gala, Yorinao Inoueb, Laurence Metsc, Itzhak Ohada | Requires cookie* | | | Title
| Photoinactivation of Photosystem II and Degradation of the D 1 Protein are Reduced in a Cytochrome b j f -Less Mutant of Chlamydomonas reinhardtii | | | | Abstract
| The effect of unoccupancy of the Q B site by plastoquinone on the photoinactivation of reac tion center II in a Cyt b jf-less mutant of Chlamydomonas reinhardtii, Bb, was investigated. In these cells the oxidation of plastoquinol generated by electron flow via RC II to plastoquinone and thus the turnover of PQH2/PQ via the Q B site are drastically reduced. Reaction center II of the mutant cells was resistant to photoinactivation relative to the control cells as demonstrated by measurements of light-induced destabilization of S2-QB charge recombination, rise in in trinsic fluorescence and loss of variable fluorescence. These parameters relate to functions in volving the reaction center II D 1 protein. The light-induced degradation of D 1 in the mutant cells was also considerably reduced, with a ;l/ 2 value of 7 h as compared, under similar condi tions, to about 1.5 h for the control cells. These results indicate that the photoinactivation of RC II and turnover of the D 1 protein are related and require occupancy of the Q B site by PQ and its light-driven reduction. | | | |
Reference
| Z. Naturforsch. 45c, 395—401 (1990); received November 24 1989 | | | |
Published
| 1990 | | | |
Keywords
| Cytochrome b j f, Chlamydomonas, D 1 Turnover, Q B, Thermoluminescence, Photoinhibition | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0395.pdf | | | | Identifier
| ZNC-1990-45c-0395 | | | | Volume
| 45 | |
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