The nucleotide sequences of barley cytoplasmic glutamate transfer RNAs and structural features essential for formation of δ-aminolevulinic acid

In chloroplasts and a number of prokaryotes, -aminolevulinic acid (ALA), the universal precursor of porphyrins, is synthesized by a multistep enzymatic pathway with glutamyl-tRNA^Glu as an intermediate. The ALA synthesizing system from barley chloroplasts is highly specific in its tRNA requirement for chloroplast tRNA^Glu; a number of other Glu-tRNAs are inactive in ALA formation although they can be glutamylated by chloroplast aminoacyl-tRNA synthetases. In order to obtain more information about the structural features defining the ability of a tRNA to be recognized by the ALA synthesizing enzymes, we purified and sequenced two cytoplasmic tRNA^Glu species from barley embryos which are inactive in ALA synthesis. By using glutamylated tRNAs as a substrate for the overall reaction, we showed that Glu-tRNA reductase is the enzyme responsible for tRNA discrimination.     

The photosynthetic apparatus of C3 and CAM-induced Mesembryanthemum crystallinum L.

Accompanying the CAM induction of Mesembryanthemum crystallinum L. grown in high salinity there are changes in the enzymes of carbon metabolism. However, there are no changes in the electron transport activities, Chla/b ratios or in the distribution of chlorophyll amongst the various pigment-protein complexes of isolated thylakoids. Hence with CAM induction there are no changes in the photochemical apparatus of M. crystallinum thylakoids. Despite comparable amounts of chlorophylla/b-proteins of photosystem II to those found in typical C₃ sun plants, both the C₃ and CAM M. crystallinum chloroplasts have relatively more photosystem II, and, concommitantly, less photosystem I complex. This is consistent with greater fluorescence emission at 685 and 695 nm, and lower emission at 735 nm (measured at 77 K) than typically found for C₃ plants, whether sun or shade species. Photoinhibition of isolated C₃ and CAM thylakoids by white light led to comparable decreases in electron transport capacities and fluorescence emission at 77 K with photosystem II being more affected than PSI. We suggest however, that the presence of more core PSII complexes relative to PSI complexes in this CAM-inducible plant, may provide an additional strategy to mitigate photoinhibition in the short-term.     

The quaternary structure of four crustacean two-hexameric hemocyanins: immunocorrelation,stoichiometry, reassembly and topology of individual subunits

Summary Two-hexameric (2×6) hemocyanins from the brachyuran crabsCancer pagurus andCallinectes sapidus, the freshwater crayfishAstacus leptodactylus and the lobsterHomarus americanus were isolated and dissociated into native subunits.The subunits of each hemocyanin were analyzed by electrophoresis and immunology. Three immunologically distinct subunit types, which were termed, and, could be identified in each case. They were isolated preparatively, and interspecifically correlated. Subunit is subdivided into several electrophoretically distinct isoforms which are immunologically closely related (Astacus) or identical (other species). InAstacus andCancer one of these isoforms was shown to dimerize and to act as inter-hexamer bridge. It represents a fourth subunit type termed. A fifth, diffuse component, which in PAGE migrated at the position of a dimer, was identified in the crossed immunoelectrophoretic patterns as denatured hemocyanin.A common feature of the four hemocyanins is the presence of 4 copies of and 8 copies of/ within the 2×6 particles. The: ratio is 4:4 in the two Astacidea and 6:2 in the two Brachyura. exists in 2 copies inAstacus andCancer which means that a single dimer- is present in a two-hexamer. This leaves 2 monomeric copies inAstacus and 4 inCancer.Every subunit from the four species except ofAstacus - was capable to form hexamers in reassembly experiments. If subunit combinations were tested, hetero-hexamers were formed preferentially. Two-hexamers were reconstituted only in the presence of all subunit types and the native subunit stoichiometry was required to obtain twohexamers in considerable yields. Factors limiting 2×6 reassembly are discussed.Authentic 2×6 molecules ofAstacus, Homarus andCancer hemocyanin were immunolabeled with subunit-specific antibody fragments (F_ab) or IgG molecules, and the resulting immuno complexes were studied in the electron microscope. A topological model of the quaternary structure of decapod 2×6 hemocyanins is derived, showing the position of each copy of the four subunit types. In this model, the inter-hexamer bridge- is surrounded by two and two subunits forming the central core of the dodecamer. Two additional and two additional subunits form the periphery together with one subunit occupying the peripheral short edges of each hexameric half structure. The model is discussed with respect to the current literature.Abbreviations PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate This paper is decicated to Professor Dr. Bernt LinzenPreliminary accounts of this work have been presented in the proceedings of a symposium at Tutzing 1985. Linzen B (ed) (1986) Invertebrate oxygen carriers. Springer, Berlin Heidelberg New York. This also includes: Stöcker et al. 1986; Markl et al. 1986) and in a review article (Markl 1986)     

New form of lignolytically active mycelium generated by immobilization of protoplasts isolated from the white rot fungi Heterobasidion annosum and Polyporus pinsitus

Summary Immobilized mycelia regenerated from immobilized protoplasts isolated from lignin-degrading Basiodiomycetes have been shown to be able to decompose specifically ¹⁴C-labelled dehydropolymers of coniferylalcohol (DHP-lignin) and monomeric lignin-related compounds more intensively than native mycelium, by decarboxylation, demethylation, ring and side chain cleavage. Protoplasts of two white rot fungi were immobilized by entrapment in Na- alginate gel and remained intact after the immobilization procedure. Within the first 3 days of incubation in culture medium, regeneration of hyphal cells occurred. Since hyphal cells regenerated from protoplasts within gel beads were hindered from stretching by the matrix, the microbial immobilized cells differed from native mycelium in terms of their morphology. The time course and extent of lignin degradation by native mycelium and regenerated mycelium of the examined white rot fungi also differed, a sign that there may also be differences between them in terms of the physiology of lignin degradation.     

Lipase production of Staphylococcus carnosus in a dialysis fermentor

Summary In a newly constructed one-vessel dialysis fermentor, a strain of Staphylococcus carnosus TM300 carrying the lipase secretion plasmid pLipPS1 was used to investigate exoenzyme and biomass production. The bacterial culture grows in an inner compartment of 21 volume, separated from a 101 nutrient broth compartment by a conventional dialysis membrane. In order to avoid substrate depletion and to prolong the growth phase, a highly concentrated nutrient broth was used. The biomass production reached 60 g cell dry weight/l. The increase in extracellular lipase concentration was directly coupled with the increase of cell mass and reached a value of 230 mg/l culture supernatant. Harvesting the cells in the late growth phase, the lipase content was about 30% of the total exoproteins in the supernatant.     

Unusual evolutionary conservation of 5S rRNA pseudogenes inAspergillus nidulans: Similarity of the DNA sequence associated with the pseudogenes with the mouse immunoglobulin switch region

Summary AllAspergillus nidulans 5S rRNA pseudogenes known so far are the result of integration of an approx. 0.2-kbp-long DNA sequence into the 5S rRNA genes. This sequence, called block C, is present in at least five copies in theA. nidulans genome and seems to be associated either with 5S rRNA genes or pseudogenes. In contrast to the 78% sequence conservation of the C-block in pseudogenes, the truncated 5 halves of the pseudogenes are very highly conserved (96.9–100%). We postulate that the 5S rRNA pseudogenes are still a subject of concerted evolution. The C-block sequence shows similarity to the switch region of the mouse heavy chain immunoglobulin gene. A characteristic motif GGGTGAG is repeated several times in both sequences; the sequence conservation is 63%.     

Diminished oestrogen sensitivity and increased ovulation rate in adult female rats after prepubertal treatment with oestrogen or pimozide

Immature female rats were implanted with oestradiol benzoate or cholesterol in the medial preoptic area at different ages, and the inhibition of the ovariectomy-induced increase of LH secretion by s.c. injected oestradiol was investigated. Medial preoptic oestrogen implants reduced the inhibition of LH secretion in 4-week-old rats, but not in younger animals. Elevation of the circulating oestrogen concentration or suppression of the central nervous dopamine activity by daily injections of oestradiol and pimozide, respectively, from Day 26 to the day of vaginal opening, i.e. during the time when the mechanism of the oestrogen-induced desensitization of the negative oestrogen feedback matures, resulted in considerable diminution of the LH-inhibiting effect of oestradiol in ovariectomized adult females. In intact cyclic rats, both prepubertal treatments led to a significant increase of the average number of eggs per ovulation that was mainly caused by reduction of the number of animals with a low ovulation rate.     

Simulated nitrogen dynamics and nitrate leaching in a perennial grass ley

A soil nitrogen model was used for a 4-year simulation of nitrogen dynamics and nitrate leaching, both during grass ley growth and after ploughing a grass ley. Model results were compared with field measurements of soil mineral-N status and leaching. A soil water and heat model provided daily values for abiotic conditions, which were used as driving variables in the nitrogen simulation. Simulated values for mineral-N levels in the soil agreed well with field data for the first 3 years of the simulation. During the final year the model predicted considerably higher levels of soil mineral-N content compared with measurements. To reach the mineral-N level measured at the time of ploughing the ley, the simulated N-uptake by plants had to be increased by 8 g N m⁻². Simulations of nitrate leaching suggested that estimates of leaching based on measurements in tile-drained plots can be considerably underestimated. Accurate quantification of leaching in tile-drained plots often requires additional information on water-flow paths. A substantial increase in simulated and measured values for the mineral-N content of the soil occurred after ploughing the ley. In the simulation, most of the increase was due to a high crop residue input and the absence of a growing crop after ploughing. Litter accumulations in the soil during the 4-year period contributed little to the increase in soil mineral-N.     

Ion Homeostasis in Chloroplasts under Salinity and Mineral Deficiency: II. Solute Distribution between Chloroplasts and Extrachloroplastic Space under Excess or Deficiency of Sulfate, Phosphate, or Magnesium

Spinach (Spinacia oleracea var “Yates”) plants grown hydroponically were exposed to an excess or deficiency of various mineral ions. Solutes were measured in leaf extracts and in isolated intact chloroplasts. Under phosphate (120 millimoles per liter NaH₂ PO₄), sulfate (200 millimolar per liter (Na₂ SO₄), or magnesium excess (150 millimolar per liter MgCl₂), concentrations of these ions in leaf extracts increased, but in chloroplasts, concentrations of all ions remained constant. Concentrations of quarternary ammonium compounds in chloroplasts increased. Under mild phosphate or magnesium deficiency, concentrations of these ions decreased in chloroplasts less than in whole leaf extracts. Under severe sulfate deficiency causing chlorosis in younger leaves, sulfate concentrations in chloroplasts remained even unchanged, despite a drastic decrease of sulfate concentrations both in green and in chlorotic leaves. Together with results from a companion study (G Schröppel-Meier, WM Kaiser 1988 Plant Physiol 87: 822-827) our data demonstrate that leaf cells are able to keep the concentrations of several mineral ions rather constant in metabolically active compartments even at extremely large variations of ion concentrations in the culture solution and in the leaves.     

Differential effects of aldosterone and ADH on intracellular electrolytes in the toad urinary bladder epithelium

Summary Quantitative electron microprobe analysis was employed to compare the effects of aldosterone and ADH on the intracellular electrolyte concentrations in the toad urinary bladder epithelium. The measurements were performed on thin freeze-dried cryosections utilizing energy dispersive x-ray microanalysis. After aldosterone, a statistically significant increase in the intracellular Na concentration was detectable in 8 out of 9 experiments. The mean Na concentration of granular cells increased from 8.9±1.3 to 13.2±2.2 mmol/kg wet wt. A significantly larger Na increase was observed after an equivalent stimulation of transepithelial Na transport by ADH. On average, the Na concentration in granular cells increased from 12.0±2.3 to 31.4±9.3 mmol/kg wet wt (5 experiments). We conclude from these results that aldosterone, in addition to its stimulatory effect on the apical Na influx, also exerts a stimulatory effect on the Na pump. Based on a significant reduction in the Cl concentration of granular cells, we discuss the possibility that the stimulation of the pump is mediated by an aldosterone-induced alkalinization.Similar though less pronounced concentration changes were observed in basal cells, suggesting that this cell type also participates in transepithelial Na transport. Measurements in mitochondria-rich cells provided no consistent results.