Jan-Eric Tillberg
Stockholm University
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Featured researches published by Jan-Eric Tillberg.
Planta | 2000
Changwen Wang; Wim Van den Ende; Jan-Eric Tillberg
Abstract. Hydroponically cultivated barley plants were exposed to nitrogen (N)-deficiency followed by N-resupply. Metabolic and genetic regulation of fructan accumulation in the leaves were investigated. Fructan accumulated in barley leaves under N-deficiency was mobilized during N-resupply. The enhanced total activity of fructan-synthesizing enzymes, sucrose:sucrose 1-fructosyltransferase (EC 2.4.1.99) and sucrose:fructan 6-fructosyltransferase (6-SFT; EC 2.4.1.10) caused by N-deficiency decreased with the mobilization of fructan during N-resupply. The activity of the barley fructan-degrading enzyme, fructan exohydrolyase (EC 3.2.1.80) was less affected by the N status. The low level of foliar soluble acid invertase activity under N-deficiency conditions was maintained during the commencement of N-resupply but increased subsequently. Further analyses by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, western blot and northern blot demonstrated that the fructan accumulation and the total activity of fructan-synthesizing enzymes correlated with the 6-SFT mRNA level. We suggest that the changes in fructan levels under N stress are intimately connected with the regulation of fructan synthetic rate which is mostly controlled by 6-SFT.
Journal of Phycology | 1984
Jan-Eric Tillberg; Tudor Barnard; John R. Rowley
Phosphorus deficiency affects the anatomy of the unicellular green alga Scenedesmus obtusiusculus Chad. and influences the distribution of other inorganic elements in the cell in addition to phosphorus. Scenedesmus was grown under standard conditions with or without phosphorus. Cells were then cultured with phosphorus under conditions favouring glycolysis, respiration, or photophosphorylation for 2 h or photosynthesis for up to 8 h. The dominating features of phosphorus starvation, were loss of phosphorus and coions from polyphosphate bodies, accumulation of starch, decrease in the volume density of ribosomes both in the chloroplast and cytoplasm, and an increase in wall thickness. Under conditions favoring photosynthesis the mass fraction for phosphorus is low after 1 h, exceptionally high by 2 h, and diminishes by 8 h. High amounts of phosphorus are also regained under conditions favoring glycolysis and photophosphorylation but not respiration. After 2 h under photosynthetic conditions the volume densities of the chloroplast, cytoplasmic ribosomes, the vacuole, and the mitochondrion increased over controls. By 8 h the relative volume of the single ramified mitochondrion had decreased slightly and recognizable segments of it were sequestered within the vacuome. The autophagic nature of the vacuole was further evidenced by the presence of ribosomes and whorls of lamellae within it. Serial sections showed that all polyphosphate granules and sequestered materials were located within a continuous vacuolar cisterna.
Journal of Plant Physiology | 1999
Chana Opaskornkul; Sylvia Lindberg; Jan-Eric Tillberg
Summary The effects of abscisic acid (10 −9 −10 −6 mol/L) were studied on light induced CO 2 -dependent O 2 evolution, sucrose synthesis, efflux of sucrose and changes in cytosolic proton concentration in mesophyll protoplasts of Pisum sativum L. cv. Fenomen. Photosynthesis did not change with increased apoplastic ABA or sucrose concentrations although sucrose synthesis decreased in the presence of ABA. In the absence of apoplastic sucrose the sucrose effiux increased and was most pronounced at 10 −7 mol/L ABA. The sucrose efflux also increased in the presence of ABA and sucrose together and was most pronounced at 10 −9 mol/L ABA and 20 mmol/L apoplastic sucrose. The cytosolic proton concentration decreased upon addition of ABA with or without sucrose, but increased upon addition of p -chloromercuribenzenesulfonic acid, a sucrose transport inhibitor. The cytosolic proton concentration decreased in the presence of 10 -9 mol/L ABA in combination with various apoplastic sucrose concentrations. In the presence of 10 -7 -10 -6 mol/L ABA in combination with apoplastic sucrose levels higher than 1 mmol/L, the cyrosolic concentration of proton increases. The results indicate that there is a relationship between the external environment and the sucrose effiux and cytosolic proton concentration in pea mesophyll protoplasts and that there is a sucrose/proton symport at the plasmalemma of pea mesophyll cells. They also show that sucrose increases the sensitivity to ABA in its action on sucrose effiux and cytosolic proton concentration.
Journal of Ultrastructure Research | 1980
Jan-Eric Tillberg; John R. Rowley; Tudor Barnard
A pH-dependent dislocation of material from polyphosphate granules, appearing as tails associated with the granules, was investigated by electron microscopy and X-ray microanalysis in cells having polyphosphate granules that are and are not readily infiltrated with embedding resin. All of the elements detected with X-ray microanalysis over polyphosphate granules (Na, Mg, Al, P, S, K, and Ca) are included in “tails” formed by artificially tilting the grids vertically following solubilization of polyphosphate granules for 30 sec on bidistilled water at pH 6. The force generated in the polyacid polyphosphate by a change in hydrogen ion concentration apparently mobilizes material from the resin-embedded granules. XRMA signals for chlorine (a resin component) are enhanced over material dislocated from granules well infiltrated with resin. Solubilization of polyphosphate in acid is expected and the present data show that this process proceeds even in the hardened epoxy resin. These results suggest the use of resin-embedded sections exposed to acidic conditions to obtain samples of in situ polyphosphate granules for analysis; this method would circumvent the contamination problems that have plagued analyses of polyphosphate granules obtained from cell homogenates.
Planta | 1966
Jan-Eric Tillberg; A. Kylin
SummaryScenedesmus cells were tried as a photosynthesizing test system for the inhibitor-β complex from potato (var. Majestic). The main effect on oxygen evolution is an inhibition of the second gush during the induction period. The formation of bound phosphate is increased by the inhibitor when the cell suspensions are shaken in the light, whereas no significant trend is observed in similar experiments in the dark. — Phloridzin inhibits the same part of oxygen evolution as inhibitor-β from potato when cells pretreated in light are the test object. Concentrations of 1 mM increase the formation of bound phosphate in light, but at 2 mM there is a decrease in this action. Phloridzin and inhibitor-β from potato have different Rf values. — The biochemical effects studied precede possible effects on cell division. — The results are discussed in relation to the localization of the site(s) of action.
Journal of Plant Physiology | 1990
Björn Thorsteinsson; Jan-Eric Tillberg
Summary Changes in carbon (C) partitioning in response to an induced phosphorus (P) or nitrogen (N) deficiency were studied in mature leaves of barley ( Hordeum vulgare L. cv. Agneta) and pea ( Pisum sativum L. cv. Marma). Optimally growing, 7-day-old pea plants or 15-day-oldbarley plants were transferred to Nor P-free but otherwise complete media for a period of 14–20 days. The responses of the two species to both types of nutrient deprivation can be divided into two phases: an early sucrose and starch accumulating phase, lasting for 8–10 days, and a late phase during which these carbohydrate levels decreased. During the first phase, the rate of the dark respiration decreased sharply whereas the CO 2 assimilation rate decreased only slightly. An increase in the photosynthesis/respiration ratio had already become apparent after 2 days of growth on the nutrient deficient media. In the later phase, the starch and sucrose pools decreased to levels even lower than the initial ones. Simultaneously the relative decrease in CO 2 assimilation rate surpassed the decrease in dark respiration rate, i.e. the photosynthesis/respiration ratio began to decrease, eventually falling below the initial value measured on day o. In both species, accumulations of starch and soluble sugars in both mature leaves and sink tissues (roots) were substantially higher in N-deprived plants than in P-deprived ones.
Plant and Soil | 1988
Paulo Jorge Pereira Duarte; P. Oscarson; Jan-Eric Tillberg; Carl-Magnus Larsson
Models of partitioning and utilization of C and N can be constructed by analysing xylem and phloem bleeding saps, as has been demonstrated e.g. in white lupin (Pate et al., 1979), and in wheat grown with a split root system (Lambers et al., 1982). When studying these parameters in relation to N availability, it is of major importance to characterize the relationship between N supply and growth. In fact, the N (or nutrient) supply can be used to control growth effectively, by allowing the plants to adapt to a chosen relative rate of N addition, which eventually leads to a linear relationship between the relative nitrogen (or nutrient) addition rate and the relative growth rate (reviewed by Ingestad 1982; Ingestad and Lund 1986). The applicability of this method in terms of control of dry matter increment and other growth parameters has been demonstrated for several species (Ericsson 1981a; b; Ingemarsson et al., 1984; Ingestad 1980, 1981; Ingestad and Lund, 1979; Linder and Rook, 1983; Linder et al., 1981) including Pisum sativum (Oscarsson and Larsson, 1986).
Photochemistry and Photobiology | 1984
Staffan Mellvig; Jan-Eric Tillberg
Abstract— Luminescence from synchronously cultured Scenedesmus obtusiusculus cells was measured with a high sensitivity photon counter. Recording of light emission was initiated 0.2 s after switching off actinic light. Luminescence decay was separated into two phases: one for decay to 104 pulses s‐1, the other for decay from 104 to 103 pulses s‐1. Most photons are emitted during the rapid decay to 104 pulses s‐l. Only small diurnal variations of the two phases could be observed in controls. Treatment with 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) decreased both the total number of photons emitted and the time required to reach the 104 pulses s‐1 level. No diurnal rhythmicity was induced by DCMU in the first phase but DCMU induced a pronounced diurnal variation in decay time in the second phase of luminescence parallelled by a periodicity in the number of photons emitted. The results indicate that DCMU interferes with the participation of PS I in luminescence. The chlorophyll alb ratio was constant during the life cycle of the cells. No relation could be observed between luminescence and the diurnal rhythmicity in photosynthesis that is characteristic for synchronized unicellular algae.
Plant Science | 1986
Thomas Olsson; Carl-Magnus Larsson; Marie Larsson; Jan-Eric Tillberg
Abstract Pyridine nucleotides in the cyanobacterium Synechococcus leopoliensis (Racib) Komarek and in the green algae Scenedesmus obtusiusulus Chod. and Ankistrodesmus braunii (Naegeli) Brunnth. were extracted with either hot NaOH, hot ethanol, hot acidic or alkaline methanol, perchloric acid (PCA) or trichloroacetic acid (TCA). Reduced pyridine nucleotides were determined with NADH- and NADPH-dependent bacterial luciferase. Oxidized nucleotides were determined after enzymatic conversion to the reduced forms. The yields of pyridine nucleotides in the extracts were compared to the relative extraction efficiency for ATP. Extraction with hot NaOH appeared satisfactory for reduced nucleotides in the green algae but less so in Synechococcus. Extraction with PCA seemed preferable for the oxidized nucleotides. The sensitivity of the bacterial luciferase assay was lowered by all extractants. Criteria for assessment of optimal extraction procedures for pyridine nucleotides are discussed.
Physiologia Plantarum | 1996
Changwen Wang; Jan-Eric Tillberg