Information about previous phosphate fluctuations is stored via an adaptive response of the high-affinity phosphate uptake system of the cyanobacterium Anacystis nidulans

The high-affinity uptake system of phosphatelimited cyanobacterium Anacystis nidulans [Synechococcus leopoliensis (Raciborski) Komarek] is characterized by a threshold value below which uptake cannot occur. Here it is shown that, if phosphate-limited cyanobacteria are challenged with a short pulse of high phosphate concentration that appreciably exceeds this threshold value, the uptake system undergoes an adaptive response, leading to the attainment of new kinetic properties and a new threshold value. These new properties are maintained for several hours after the pulse. A notable characteristic of this new state is a wide linear dependence of the uptake rate on the external phosphate potential that is a function of the driving force of the uptake process. According to theoretical arguments it is shown that this “linear operation mode” can be explained by the simultaneous operation of several uptake systems with different, staggered threshold values and kinetic properties. Moreover, the new linear uptake properties, in turn, reflect the prehistory of phosphate supply experienced by the population. The consequences of this result with regard to environmental fluctuations of the phosphate concentration in lakes are discussed.     

INFLUENCE OF FLUCTUATING PHOSPHATE SUPPLY ON THE REGULATION OF PHOSPHATE UPTAKE BY THE BLUE-GREEN ALGA ANACYSTZS NIDULANS1

The blue-green alga Anacystis nidulans Drouet (Synechococcus leopoliensis Raciborski) cultivated under phosphate-limited conditions adopts a threshold value in the nanomolar range below which uptake ceases. In this study, we investigated the influence of phosphate pulses on the regulation of uptake behavior during reestablishment of the threshold value. Short-term pulses had only a slight effect on uptake kinetics and, hence, on the threshold value, even if the population had been exposed several times to elevated concentrations above the steady-state level in the growth medium. The threshold value was also practically insensitive to the amount of phosphate stored during these short-term fluctuations. Long-term phosphate pulses resulted in a transition to a metastable state that was characterized by a severalfold higher threshold value. This transition, apparently an adaptation to the transiently elevated phosphate concentrations, was further studied by following the influx of ³²P-phosphate at constant external concentrations and was shown to be complete after a period of 10–20 min. After adaptation to pulses, the uptake behavior followed a linear flow-force relation over a wide range of external concentrations. This behavior was explained by the simultaneous operation of at least two uptake systems with different, but coordinated kinetic parameters. This linear flow-force relation facilitated a direct determination of the threshold value from uptake measurements. For applicability in the field the force-flow relation can be a diagnostic tool to assay for fluctuating phosphate and to establish threshold values below the normal measurable range .     

Zur Kompartimentierung der Synthese von Mono- und Sesqui-Terpenen des ätherischen Öls beiPoncirus trifoliata

Zusammenfassung In der Frucht vonPoncirus trifoliata liegen in der Außenschale Drüsenzellkomplexe, die ein monoterpenreiches ätherisches Öl mit geringem Anteil an Sesquiterpenen und O-haltigen Substanzen produzieren. Ähnlich aussehende Exkretzellkomplexe aus den Saftschläuchen enthalten hauptsächlich Sesquiterpenkohlenwasserstoffe (STKW) und O-haltige Komponenten und sehr wenig Monoterpenkohlenwasserstoffe (MTKW). Im Schalenöl konnten nach gaschromatographischer Trennung mit Hilfe der Massenspektrometrie 19 Komponenten identifiziert werden, im Saftschlauchöl 25.Elektronenmikroskopische Aufnahmen der jüngsten Drüsenzellen beider Drüsenkomplexe lassen erkennen, daß beide Terpenklassen wahrscheinlich hauptsächlich bzw. ausschließlich plastidär entstehen.Exogen angebotenes¹⁴CO₂ wird zunächst überwiegend in die MTKW eingebaut, erst später nimmt die Markierung der STKW und O-haltigen Komponenten stark zu. Über den Ferntransportweg angebotenes¹⁴C-Leucin führt anfangs zu einer starken Markierung der STKW und O-haltigen Komponenten, erst später verschiebt sich der Einbau etwas mehr in Richtung MTKW. Als Hauptursache für den differenten Einbau wird das Vorhandensein zweier Typen von Drüsenzellkomplexen mit unterschiedlichen Syntheseleistungen angesehen.Die aus dem¹⁴CO₂ in der Außenrinde gebildeten Assimilate werden zuerst in das MTKW-reiche Öl der Schalenexkretbehälter eingebaut. Die überwiegend STKW erzeugenden Saftschlauchbehälter werden erst später beliefert. Beim Leucinangebot über die Fruchtstiele scheint es gerade umgekehrt zu verlaufen. Die aufeinanderfolgenden Maxima der Ölproduktion in den beiden Drüsenzellkomplex-Typen und die Änderung des Komponentenspektrums ihres ätherischen Öls im Verlauf der Vegetationsperiode tragen ebenfalls zu einem je nach Jahreszeit unterschiedlichen Einbau in die MTKW und STKW bei.

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Compartmentation of mono- and sesqui-terpene biosynthesis of the essential oil inPoncirus trifoliata

Summary The fruit ofPoncirus trifoliata shows glandular cell complexes in the exocarp, which produce a volatile oil rich in monoterpenes but poor in sesquiterpenes and oxigenated compounds. The juice vesicles of the endocarp possess similar cell complexes mainly containing sesquiterpenes and oxigenated compounds, whereas monoterpenes only occur in small amounts. By the use of combined gas chromatography-mass spectrometry 19 components of the rind oil and 15 compounds of the endocarp oil could be identified.As demonstrated by electron microscopy the terpenes most probably are synthesized predominantly, if not exclusively in plastids. As shown by gasradiochromatography radioactive precursors (¹⁴CO₂ and¹⁴C-leucine) are incorporated into mono- and sesqui-terpenes to a different extent.This is due to two gland types producing essential oils of different composition with regard to their mono- and sesqui-terpene percentage. In fruit development the exocarp glands differentiate earlier than the endocarp glands do. The activity of exogenously applied¹⁴CO₂ first reaches the peripheral glands and later on appears in the interior glands. Depending upon the growth season, labelled leucine transported by the conducting tissues from lower plant parts leads to a high specific activity of the sesqui-terpenes and oxigenated compounds. It could be argued that in this instance the glands of the pulp are better provided with precursors than the exocarp glands. The successive maxima of essential oil production in both glandular complexes, and the changes in the concentration of individual oil constituents during the ontogeny of the fruit also contribute to different incorporation ratios of radioactive precursors into mono- and sesqui-terpenes.

     

Microspore cultures as donor tissue for the initiation of embryogenic cell suspensions in barley

We have initiated embryogenic cell suspension cultures of barley (Hordeum vulgare L.) Igri from isolated microspore cultures. Data were obtained on the time required for establishment, frequency of establishment, i.e. number of calluses out of the total number of initiations giving rise to suspensions, and embryogenic capacity of the suspension cultures. For comparison, establishment of embryogenic cell suspensions from callus derived from immature zygotic embryos of Igri, Dissa and Golden Promise was also carried out. The results revealed that embryogenic suspension cultures were established in half the time and with a seven-fold higher frequency from microspore cultures than from zygotic embryo-derived calluses. The suspension cultures were still capable of embryo formation after two years. However, only albino plantlets were regenerated. For comparison, long term callus cultures derived from microspores, anthers and zygotic embryos were established. From the anther and zygotic embryo-derived callus cultures green plants were continuously regenerated, whereas the microspore-derived callus cultures lost this ability after the second subculture.     

Histochemical evidence for lysosomal storage of acid glycosaminoglycans in splenic cells of rats treated with tilorone

Summary Tilorone, an agent with antiviral and antitumor activities, has previously been reported to produce clear cytoplasmic vacuoles in many cell types of the rat. The present study on rat spleen was planned to investigate the ultrastructural and histochemical features of the tilorone-induced vacuoles occurring in sinus endothelium, trabecular smooth muscle cells, and macrophages of the red pulp. Evidence was obtained that the vacuoles represent lysosomes overloaded with acid glycosaminoglycans (aGAG). The main purpose of the present study was to overcome the technical difficulties of preserving the intralysosomal storage materials which were highly water-soluble and non-fixable by aldehyde fixatives. Preservation, at least for the light microscopical level, was achieved by freeze drying and by means of cationic dyes which served also to characterize the storage materials on the basis of their acidities. Tissue slices were used to determine the critical MgCl₂ concentration necessary to abolish Alcian blue staining; cartilage and mast cells served as references. For the storage material in sinus endothelium, the critical MgCl₂ concentration was found to be >0.7 M, as compared to >0.5 M for cartilage and >0.9 M for mast cells. The storage materials in trabecular cells and macrophages were slightly less acidic than cartilagineous matrix and more heterogeneous than that in sinus endothelium. Ultrastructurally, positive staining with high iron diamine (HID) confirmed the presence of aGAG within the tilorone-induced vacuoles.     

Number of the repetitive euchromatic 5S RNA genes in polyploid tissues of Drosophila hydei

Repetitive genes localized within heterochromatin, such as the rDNA in Drosophila, replicate several steps less than the bulk DNA during polytenization. The 5S RNA genes of Drosophila hydei were chosen as a model system to inquire whether underreplication also occurs if the repetitive gene cluster is localized in the euchromatin. Filter saturation hybridization showed that there are 320 5S RNA gene copies in the haploid genome. Setting the diploid number at 100%, it was found that the DNA of polytene salivary glands reached only 79% of this value, and the DNA of polyploid ovarian tissue reached only 72% of this value. Although the latter two saturation values are less than the diploid standard, they are not as low as the 50% saturation value predicted for a one-step reduction. This may reflect a slower replication of these genes compared to the bulk DNA. These results imply that underreplication is not a general characteristic of repetitive genes but depends on their localization in the euchromatic or heterochromatic part of the genome.