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1994 (1)
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1Author    Margarete Hoffmans-Hohn, W. Olfgang, M. Artin, Klaus BrinkmRequires 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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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0791.pdf 
 Identifier    ZNC-1984-39c-0791 
 Volume    39 
2Author    I. Perewoska, C. Vernotte, M. Picaud, C. AstierRequires 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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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0580.pdf 
 Identifier    ZNC-1992-47c-0580 
 Volume    47 
3Author    Alexander Pazur, Hugo ScheerRequires 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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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0690.pdf 
 Identifier    ZNC-1992-47c-0690 
 Volume    47 
4Author    E. B. Racht, A. TrebstRequires 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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 TEI-XML for    default:Reihe_C/49/ZNC-1994-49c-0439.pdf 
 Identifier    ZNC-1994-49c-0439 
 Volume    49 
5Author    Susana Shochata, Noam Adira, Alma Gala, Yorinao Inoueb, Laurence Metsc, Itzhak OhadaRequires 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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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0395.pdf 
 Identifier    ZNC-1990-45c-0395 
 Volume    45