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At least 19 recordsLinked to original sources
PubMed1992

Identification of two clock proteins in Acetabularia cliftonii and construction of cDNA libraries from Acetabularia cliftonii and Acetabularia mediterranea.

1. Two clock proteins were identified in A. cliftonii. The first has a molecular weight (mol. wt) of 200 kDa (P200) and its synthesis shows a 24 hr periodicity. The second has mol. wt of 130 kDa (P130) and shows a semicircadian rhythm with a periodicity of about 12 hr. 2. cDNA libraries from A. cliftonii and A. mediterranea were prepared by cloning cDNA in lambda gt10 and lambda gt11, respectively. 3. One clone each of the two libraries hybridized with the human beta-actin pseudogene. One clone of the A. mediterranea and 4 clones of the A. cliftonii libraries hybridized to Chlamydomonas heat-shock gene.

Acetabularia↗
PubMed1994

Purification and characterization of a membrane-bound ATPase from Acetabularia cliftonii that corresponds to a Cl(-)-translocating ATPase in Acetabularia acetabulum.

A Mg(2+)-ATPase was solubilized from membranes of Acetabularia cliftonii using nonanoyl-N-methylgluconamide and purified by ion-exchange and gel permeation chromatography. One active ATPase fraction after Mono Q chromatography had a specific activity of 10 units/mg of protein. Judged from subunit composition [54 (a), 50 (b) with a fainter band around 40 kDa], catalytic properties, and N-terminal amino acid sequence of the b subunit, the isolated enzyme was comparable to the Cl(-)-ATPase of Acetabularia acetabulum. Immunological characterization of both subunits showed significant similarity to the F type of ATPase. Cl(-)-transport activity was observed by reconstitution studies into liposomes.

Acetabularia↗
PubMed1984

Enhancer-controlled expression of the simian virus 40 T-antigen in the green alga Acetabularia.

Nuclei from Acetabularia mediterranea were isolated, microinjected with simian virus 40 (SV40) DNA and fused with cytoplasts from the same species. Various times after fusion of the injected nuclei the fusion products were screened for expression of the T-antigen by indirect immunofluorescence. One and two days after injection a bright fluorescence could be observed in the nuclei of Acetabularia. On the basis of this immunofluorescence we conclude that in Acetabularia cells the T-antigen is expressed and accumulated in the nucleus. Moreover, evidence is presented that the Acetabularia cell recognizes the SV40 enhancer sequence. The expression product of the SV40 DNA appears significantly earlier than the expression products of other foreign genes in Acetabularia. The results suggest that the well characterized SV40 can be used as a vector system for the introduction and expression of foreign genes in Acetabularia.

Cell Nucleus↗
PubMed1992

Isolation and characterization of different forms of thioredoxins from the green alga Acetabularia mediterranea: identification of an NADP/thioredoxin system in the extrachloroplastic fraction.

A procedure has been developed for the simultaneous purification to apparent homogeneity of chloroplast thioredoxins f and m, and nonchloroplast thioredoxin h, from the green alga Acetabularia mediterranea. In the chloroplast fraction, three thioredoxins were isolated: one f type thioredoxin (Mr 13.4 kDa) and two m type thioredoxin forms (Mr of 12.9 and 13.8 kDa). A Western blot analysis of crude and purified chloroplast thioredoxin preparations revealed that Acetabularia thioredoxin m was immunologically related to its higher-plant counterparts whereas thioredoxin f was not. In the nonchloroplast fraction, a single form of thioredoxin h (Mr 13.4 kDa) and its associated enzyme NADP-thioredoxin reductase (NTR) were evidenced. Acetabularia NTR was partially purified and shown to be an holoenzyme composed of two 33.0-kDa subunits as is the case for other plant and bacterial NTRs. Similarity was confirmed by immunological tests: the algal enzyme was recognized by antibodies to spinach and Escherichia coli NTRs. Acetabularia thioredoxin h seemed to be more distant from higher-plant type h thioredoxins as recognition by antibodies to thioredoxin h from spinach and wheat was weak. The algal thioredoxin h was also slightly active with spinach and E. coli NTRs. These results suggest that in green algae as in the green tissues of higher plants the NADP and chloroplast thioredoxin systems are present simultaneously, and might play an important regulatory role in their respective cellular compartments.

Acetabularia↗
PubMed1978

Translation of tobacco mosaic virus RNA In Acetabularia cell cytoplasm.

Isolated Acetabularia nuclei were microinjected with Tobacco Mosaic Virus RNA and then implanted into an anucleate posterior fragment of an Acetabularia cell. Injected RNA was translated in the Acetabularia cytoplasm from the first to twelfth day after implantation of the nuclei. The production of specific virus proteins was detected and localized in the Acetabularia cytoplasm by an immunofluorescence precipitation technique.

Acetabularia↗
PubMed1985

Tandemly repeated nonribosomal DNA sequences in the chloroplast genome of an Acetabularia mediterranea strain.

A purified chloroplast fraction was prepared from caps of the giant unicellular green alga Acetabularia mediterranea (strain 17). High molecular weight DNA obtained from these chloroplasts contains at least five copies of a 10-kilobase-pair (kbp) sequence tandemly arranged. This unique sequence is present in DNA from chloroplasts of all stages of the life cycle examined. A chloroplast rDNA clone from mustard hybridized with some restriction fragments from Acetabularia chloroplast DNA but not with the repeated sequence. An 8-kbp EcoRI-Pst I fragment of the repeated sequence was cloned into pBR322 and used as a hybridization probe. No homology was found between the cloned 8-kbp sequence and chloroplast DNA from related species Acetabularia crenulata or chloroplast DNA from spinach.

Acetabularia↗
PubMed1983

Gene expression in Acetabularia. III. Comparison of stained cytosolic proteins and in vivo and in vitro translation products.

A comparison of stained cytosolic proteins, in vivo 80 S ribosome translation products and in vitro translation products of poly(A)+ RNA from three species of Acetabularia was performed after characterization of their molecular weights and isoelectric points via two-dimensional electrophoresis. A total of 803 stained proteins, and 121 in vivo and 77 in vitro translation products, representing the most abundant proteins in each category, were analysed. In interspecies comparisons, approximately 10% of the stained proteins were common to all three species and more than 50% were found to be species-specific. Approximately 25% of the in vivo translation products were common to all three species and more than 30% were found to be species-specific. The majority of the in vivo and in vitro translation products were detected by one or both of the other methods employed. Even though the analysis was limited to the most abundant proteins detected by each of the three methods and to one stage of development, the results suggest that the translation of some proteins is not regulated, that the in vivo translation of others, whose mRNA is present and translated in vitro, is turned off while the translation in vivo of others is enhanced relative to the total. This feature makes them candidates for stage-specific proteins. The results provide a firm basis for the extended analysis of the biological activity of heterologous messenger RNA in Acetabularia cytoplasm and for a more complete cataloguing of the mRNA population and translational activity at different stages in the development of Acetabularia.

Acetabularia↗
PubMedDate not supplied

[Comparison of the energy characteristics of Acetabularia membranes in light and darkness].

Energetic parameters of the membrane of marine alga Acetabularia were compared at light and dark during the action potential (AP). Direct current resistance of the resting membrane at dark as well as at light is of the order 1000-5000 omega-cm2 without considerable difference. The maximum resistance of the excited Acetabularia membrane is somewhat increased at dark as compared to its value at light. The maximum power of the membrane system and that of its regulating mechanism along with the energy dissipating AP at light exceed the same values at dark. The dissipating energy and the work Acetabularia cell performs during the AP are also compared for light and dark conditions.

Acetabularia↗
PubMedDate not supplied

[Effect of the ionic composition of the environment on the intracellular potential of the alga Acetabularia].

Concentration of K+-, Na+-, Mg++-, Ca++-, Cl-ions defined in Acetabularia crenulata cell was the same as that of Acetabularia mediterranea, both were cultivated under the same conditions. At the variations of the ionic composition of the external medium it has been shown that the potential of Acetabularia (A.) cell depends on K+-, Cl-ions and alga A. can accumulate K+- Cl-ions and lose Na+, Mg++ ones when there is a deficiency of these ions in the medium. Na+-, Mg++-ions participation in the generation of the rest potential of Alga A. is insignificant. K+- ion is able to change the ionic permeability of the membrane. There is a possibility of the existance of essential H+-, -OH-, or HCO3- ions flux in A. cell.

Acetabularia↗
PubMedDate not supplied

[Synthesis of virus-specific products following introduction of tobacco mosaic virus RNA pereparations and the native virus into acetabularia].

The possibility to synthesize the viral-specific products after microinjection of Tobacco mosaic virus (TMV) preparations and the TMV RNA into the single-celled seaweed Acetabularia was studied. The accumulation of the newly synthesized protein and double-stranded RNA 24 hours after injection of TMV RNA and native virus preparations was demonstrated by immunological and immunofluorescent methods. The virus titer sharply dropped 3--4 hours after introduction into Acetabularia and in 48 hours it reached a maximum level. The presented data showed the possibility of TMW RNA replication and translation involving formation of viral-specific proteins and the production of a virus of full value in the Acetabularia cell.

Acetabularia↗
PubMed1978

Study of the distribution and biological effects of 3H in the algae Acetabularia, Chlamydomonas and Porphyra.

Freshwater and marine algae are particularly useful for studying the radioactive contamination of aquatic systems. Acetabularia, Chlamydomonas and Porphyra were used to investigate the uptake and eventual biological effects of tritium. When the Acetabularia are grown in the presence of tritiated water, a significant amount of 3H is incorporated in the total nucleic acids and protein fraction. Chloroplasts of Acetabularia were isolated from whole cells and their DNA purified by the agarose procedure, before radioactivity analysis: a significant amount of 3H was incorporated into the chloroplast genome. Chlamydomonas was grown on minimal medium containing increasing concentrations of tritiated water. The increase in cell number was checked by microscope counting. The generation time was 9.6 h and seemed not affected even by the highest 3H concentration. Parallel experiments have shown that an appreciable amount of 3H was incorporated into the total organic matter of the plants. In the case of Porphyra, it was found that a very low level of 3H was incorporated into the total DNA of the plant.

Adenine↗
PubMed1991

Ion fluxes in Acetabularia: vesicular shuttle.

Ion flux relations in the unicellular marine alga Acetabularia have been investigated by uptake and washout kinetics of radioactive tracers (22Na+, 42K+, 36Cl- and 86Rb+) in normal cells and in cell segments with altered compartmentation (depleted of vacuole or of cytoplasm). Some flux experiments were supplemented by simultaneous electrophysiological recordings. The main results and conclusions about the steady-state relations are: the plasmalemma is the dominating barrier for translocation of K+ with influx and efflux of about 100 nmol.m-2.sec-1. K+ passes three- to sevenfold more easily than Rb+ does. Under normal conditions, Cl- (the substrate of the electrogenic pump, which dominates the electrical properties of the plasmalemma in the resting state) shows two efflux components of about 17 and 2 mumol.m-2.sec-1, and a cytoplasmic as well as vacuolar [Cl-] of about 420 mM ([Cl-]o = 529 mM). At 4 degrees C, when the pump is inhibited, both influx and efflux, as well as the cellular [Cl-], are significantly reduced. Na+ ([Na+]i: about 70 mM, [Na+]o: 461 mM), which is of minor electrophysiological relevance compared to K+, exhibits rapid and virtually temperature-insensitive (electroneutral) exchange (two components with about 2 and 0.2 mumol.m-2.sec-1 for influx and efflux). Some results with Na+ and Cl- are inconsistent with conventional (noncyclic) compartmentation models: (i) equilibration of the vacuole (with the external medium) can be faster than equilibration of the cytoplasm, (ii) absurd concentration values result when calculated by conventional compartmental analysis, and (iii) large amounts of ions can be released from the cell without changes in the electrical potential of the cytoplasm. These observations can be explained by the particular compartmentation of normal Acetabularia cells (as known by electron micrographs) with about 1 part cytoplasm, 5 parts central vacuole, and 5 parts vacuolar vesicles. These vesicles communicate directly with the central vacuole, with the cytoplasm and with the external medium.

Acetabularia↗
PubMed1976

Voltage dependent potassium fluxes and the significance of action potentials in Acetabularia.

Membrane potential, Vm, and K+ (86Rb+) fluxes have been measured simultaneously on individual cells of Acetabularia mediterranea. During resting state (resting potential approx. -170 mV) the K+ influx amounts to 0.24-0.6 pmol-cm-2-s-1 and the K+ efflux to 0.2-1.5 pmol-cm-2s-1. According to the K+ concentrations inside and outside the cell (40:1) the voltage dependent K+ flux (zero at Vm = EK = -90 mV) is stimulated approx. 40-fold for Vm more positive than EK. It is calculated that during one action potential (temporary depolarization to Vm more positive than EK) a cell looses the same amount of K+, which leaks in during 10-20 min in the resting state (Vm = -170 mV). Since action potentials occur spontaneously in Acetabularia, they are therefore suggested to have a significant function for the K+ balance of this alga.

Acetabularia↗
PubMed1979

Cable properties and compartmentation in Acetabularia.

The electrical cable properties of three different compartmentation types of Acetabularia cells have been investigated. These three types were: normal cells, 'stumps' (filled with cytoplasm, no central vacuole) and 'tubes' (cytoplasm depleted vacuoles). The latter two types have been obtained by centrifugation of normal cells. Qualitatively, the characteristic biphasic voltage response upon rectangular current pulses is the same in these three types. Quantitatively, however, the two conductances which can be obtained from the biphasic voltage response as well as the apparent capacity of several F . m-2 which derives from the large time constant of the second phase, are drastically increased in stumps and decreased in tubes compared to normal cells. The resting potential is a few mV more negative in stumps, and more positive in tubes, than in normal cells. Based on the existence of the high resting potential and the apparent large capacity in the non-vacuolated stumps, it is concluded that the electrogenic Cl- pump of Acetabularia is located in the plasmalemma membrane and that the apparent large capacity is not a result of the complicated membraneous organisation of the vacuolar system. Several possibilities are discussed, in relation to the quantitative correlation between intracellular compartmentation and electrical membrane parameters.

Acetabularia↗
PubMed1978

The kinetic complexity of Acetabularia chloroplast DNA.

The kinetic complexity of Acetabularia cliftonii chloroplast DNA is 1.52 +/- 0.26 . 10(9) daltons, compared to 0.2 .10(9) daltons for Chlamydomonas chloroplast DNA. There is an average of three genomes per chloroplast. The unusually large size of the Acetabularia genome may reflect the ancient evolutionary history of this organism.

Acetabularia↗
PubMed1976

Temperature dependence of cycloheximide-sensitive phase of circadian cycle in Acetabularia mediterranea.

The biochemical nature of the circadian regulatory system that controls many cellular activities is still unclear. Recent results obtained from the application of protein synthesis inhibitors to individual Acetabularia cells expressing circadian rhythms of photosynthesis indicate that some protein(s) must be synthesized on 80S ribosomes during a discrete part of each cycle to insure correct time-keeping. A comparative study of the effects of brief cycloheximide treatments on cells investigated at different temperature has revealed that the phase of cycloheximide sensitivity is 4-6 hr longer and occurs about 8 hr later in the cycle when cells are kept at 20 degrees rather than 25 degrees. Temperature is known to influence the function of the circadian regulatory system in Acetabularia, but the effect on frequency is small (Q10 approximately equal to 0.8) due to the existence of a temperature-compensating feature. The large effects of temperature observed here thus favor the interpretation that protein synthesis on 80S ribosomes, while providing an essential component of the circadian timing mechanism, does not itself generate the period of the photosynthesis rhythm.

Acetabularia↗
PubMed1986

Evidence for a circaseptan and a circasemiseptan growth response to light/dark cycle shifts in nucleated and enucleated Acetabularia cells, respectively.

Nucleated as well as enucleated Acetabularia mediterranea cells were subjected to 14 different patterns of shifts in a regimen of 12 hr of light alternating with 12 hr of darkness in four 30-day long experiments. With one exception, which might be due to a circannual modulation, these experiments showed that nucleated cells had maximal growth rates when a shift was performed every 7th or 15th day. In enucleated cells, maxima were observed on shift schedules that were about 3-4 days rather than about 7 days apart. The results indicate that in the unicellular green alga Acetabularia a rhythm of about 7 days (circaseptan) exists and that removal of the nucleus results in a circaseptan frequency multiplication.

Acetabularia↗