Temperature characteristics and adaptive potential of wheat ribosomes

The translational efficiency of wheat ribosomes was studied as a function of an in vivo temperature pretreatment of wheat seedlings (Triticum aestivum L.). Ribosomes were isolated from heat-pretreated (36°C) and reference (4°C, 20°C) wheat seedlings. The efficiency of the ribosomes in translating polyuridylic acid was assayed. Ribosomes from heat-pretreated seedlings exhibit a threefold enhanced incorporation rate of phenylalanine as compared to ribosomes from wheat seedlings adapted to 20 or 4°C. This difference develops within 24 hours after onset of the heat treatment of seedlings following a 3 hour lag phase. The temperature induced changes can be traced back to the cytoplasmic ribosomes, since cycloheximide inhibits translation almost completely. Thermal inactivation of ribosomes occurs at 45°C, irrespective of the temperature pretreatment of the wheat seedlings. Specific differences in the yield of ribosomes, in the polyribosomal profiles, and in the apparent Arrhenius' activation energy of protein synthesis were observed depending on the age and the temperature pretreatments. The results presented here are considered an important molecular correlation to phenotypical temperature adaptation of in vivo protein synthesis in wheat (M Weidner, C Mathée, FK Schmitz 1982 Plant Physiol 69: 1281-1288).     

Ribosome-associated protein that inhibits translation at the aminoacyl-tRNA binding stage

We have recently isolated and characterized a novel protein associated with Escherichia coli ribosomes and named protein Y (pY). Here we show that the ribosomes from bacterial cells growing at a normal physiological temperature contain no pY, whereas a temperature downshift results in the appearance of the protein in ribosomes. The protein also appears in the ribosomes of those cells that reached the stationary phase of growth at a physiological temperature. Our experiments with cell-free translation systems demonstrate that the protein inhibits translation at the elongation stage by blocking the binding of aminoacyl-tRNA to the ribosomal A site. The function of the protein in adaptation of cells to environmental stress is discussed.     

Inactivation of eucaryotic ribosomes by the toxic plant proteins abrin and ricin

The effect of abrin and ricin on protein synthesizing systems from different sources was studied. The protein synthesis in a cell-free system from rabbit reticulocytes and from rat liver was strongly inhibited by the toxins, whereas a system from E. coli was not affected. Separate treatments of ribosomes and postribosomal supernatant from a rabbit reticulocyte lysate showed that the site of action of the toxins is on the ribosomes. The inactivation of the rabbit reticulocyte lysate by the toxins was a function of the incubation time and temperature. Protein synthesis was not necessary for the toxins to exert their effect. The data indicate that abrin and ricin act only on the eucaryotic type of ribosomes, and that they exert their effect by enzymatic action.     

A two-dimensional numerical study of spatial pattern formation in interacting Turing systems

For many years Turing systems have been proposed to account for spatial and spatiotemporal pattern formation in chemistry and biology. We extend the study of Turing systems to investigate the rôle of boundary conditions, domain shape, non-linearities, and coupling of such systems. We show that such modifications lead to a wide variety of patterns that bear a striking resemblance to pigmentation patterns in fish, particularly those involving stripes, spots and transitions between them. Using the Turing system as a metaphor for activator—inhibitor models we conclude that such a mechanism, with the aforementioned modifications, may play a rôle in fish patterning.     

The rôle of amino acids in diet intake and selection and the utilization of dipeptides by Aphis fabae

Eight amino acids considered essential for the growth of Aphis fabae were investigated in relation to their rôle in protein synthesis and phagostimulation. When either alanine, histidine, methionine, proline, or serine were omitted from synthetic diets, intake was lower than that of the complete diet over a 4 day period. The omission of cysteine, phenylalanine, or tyrosine failed to reduce diet intake. Histidine and methionine were considered essential for protein synthesis and did not act as phagostimulants; alanine and proline, however, appeared to act primarily as phagostimulants. When subjected to choice chamber tests aphid larvae had a severely limited ability to select between complete diets and ones deficient in a single amino acid. If methionine and glycine were replaced by either glycyl l-methionine or l-methionyl glycine the size attained by larvae during growth was less than that of aphids reared on a complete diet but greater than that of aphids reared on diets deficient in both dipeptides and methionine.     

Translation of poly(U) on ribosomes from Streptomyces aureofaciens

Slowly cooled cells of Streptomyces aureofaciens contained mainly tight-couple ribosomes. Maximum rate of polyphenylalanine synthesis on ribosomes of S. aureofaciens was observed at 40°C, while cultures grew optimally at 28°C. Ribosomes of S. aureofaciens differed from those of E. coli in the amount of poly(U) required for maximum synthetic activity. The polyphenylalanine-synthesizing activity of E. coli ribosomes was about 3-times higher than that of S. aureofaciens ribosomes. The addition of protein S1 of E. coli or the homologous protein from S. aureofaciens had no stimulatory effect on the translation of poly(U). In order to localize alteration(s) of S. aureofaciens ribosomes in the elongation step of polypeptide synthesis we developed an in vitro system derived from purified elongation factors and ribosomal subunits. The enzymatic binding of Phe-tRNA to ribosomes of S. aureofaciens was significantly lower than the binding to ribosomes of E. coli. This alteration was mainly connected with the function of S. aureofaciens 50 S subunits. These subunits were not deficient in their ability to associate with 30 S subunits or with protein SL5 which is homologous to L7/L12 of E. coli.     

Role of the Y organ and the effect of ecdysterone during the regeneration of an appendage in the oniscoid Porcellio dilatatus

The rôle of the moulting hormone in regeneration was studied in Porcellio dilatatus by destroying the Y-organs (moulting glands) and by injecting synthetic ecdysterone. The destruction of the Y-organs prevents the formation of the regeneration bud of the limb. Several successive injections of a very weak solution of ecdysterone allow the formation of a regeneration bud in animals without Y-organs. A single injection of ecdysterone at a dose which induces apolysis blocks regeneration by making all the epidermal cells secrete cuticle, including those of the regeneration bud.     

Plant desiccation and protein synthesis: an in vitro system from dry and hydrated mosses using endogenous and synthetic messenger ribonucleic Acid

The conditions and requirements for an in vitro protein synthesizing system from the moss Tortula ruralis are outlined. Using this system the effects of desiccation, achieved quickly or slowly, were studied. Slowly dried moss retained fewer polyribosomes on desiccation but more active ribosomes than rapidly dried moss. Even in the completely desiccated moss the polyribosomes and/or free ribosomes present have retained their synthetic capacities. On rehydration, the slowly dried moss resumed protein synthesis more quickly than moss previously desiccated rapidly. Moss ribosomes are cycloheximide sensitive and chloramphenicol insensitive and thus the major protein synthesis occurs within the cytoplasm on rehydration. Extracted polyribosomes per se can withstand desiccation to a significant extent, suggesting that protection by the cytoplasm might not be necessary. The aquatic moss Hygrohypnum luridum can retain polyribosomal and ribosomal activity during desiccation, but this decreases greatly on rehydration.     

The influence of temperature upon polysomes of spermatids of rat testes

Incorporation of [³H]phenylalanine into protein by a reconstituted lysate subcellular system (ribosomes plus high-speed supernatant) from rat spermatids was measured at 34°C after 5 minutes preincubation of one component at 0°C while the other component was incubated at temperatures from 30°C to 40°C. Preincubation at temperatures above 34°C inhibits the ribosomal activity but not the high-speed supernatant activity. The incubation of lysate above 34°C results from a dissociation of polysomes to monosomes. These results indicate that ribosomes are the most sensitive component to the increased temperature on protein synthesis in lysate cell free system by spermatids and that the inhibition of protein synthesis in spermatids above 34°C is at least partly explained by the breakdown of polysomes in these cells.     

α-Farnesene,a naturally occurring oviposition stimulant for the codling moth, Laspeyresia pomonella

In laboratory·bioassays gravid female codling moths (Laspeyresia pomonella) were stimulated to oviposit by natural α-farnesene, which is comprised of (E,E)-α- and (Z,E)-α-farnesene, and by synthetic (E,E)-α-farnesene.The probable rôle of α-farnesene in fruit location by the codling moth is briefly discussed.     

Composés bromés de Rytiphlea tinctoria (Rhodophyceae)

Four aromatic bromo compounds have been isolated from the ethanolic extract of Rytiphlea tinctoria after treatment with diazomethane: 2,4-dibromo-1,3,5-trimethoxy-benzene,5,6,3′,5′-tetrabromo-3,4,2′,4′,6′-pentamethoxydiphenylmethane, 5,6-dibromo-3,4-dimethoxy-benzyl alcohol and its ethyl ether. In addition to sterols, amino acids, this extract also contains quinonoid bromo-pigments which could play a rôle in photosensitisation of chlorophylls, a rôle normally taken by the phycobilins, in other Rhodophyceae.     

Effect of Temperature on In Vivo Protein Synthetic Capacity in Escherichia coli

In this report, we examine the effect of temperature on protein synthesis. The rate of protein accumulation is determined by three factors: the number of working ribosomes, the rate at which ribosomes are working, and the rate of protein degradation. Measurements of RNA/protein ratios and the levels of individual ribosomal proteins and rRNA show that the cellular amount of ribosomal machinery in Escherichia coli is constant between 25 and 37°C. Within this range, in a given medium, temperature affects ribosomal function the same as it affects overall growth. Two independent methodologies show that the peptide chain elongation rate increases as a function of temperature identically to growth rate up to 37°C. Unlike the growth rate, however, the elongation rate continues to increase up to 44°C at the same rate as between 25 and 37°C. Our results show that the peptide elongation rate is not rate limiting for growth at high temperature. Taking into consideration the number of ribosomes per unit of cell mass, there is an apparent excess of protein synthetic capacity in these cells, indicating a dramatic increase in protein degradation at high temperature. Temperature shift experiments show that peptide chain elongation rate increases immediately, which supports a mechanism of heat shock response induction in which an increase in unfolded, newly translated protein induces this response. In addition, we find that at low temperature (15°C), cells contain a pool of nontranslating ribosomes which do not contribute to cell growth, supporting the idea that there is a defect in initiation at low temperature.     

Two Hydrolase Resistant Analogues of Diadenosine 5′,5″′-P,P-Triphosphate for Studies with FHIT,The Human Fragile Histidine Triad Protein¶

Abstract

The design and synthesis of analogues of diadenosine 5′,5″′-P,P-triphosphate that are resistant to pyrophosphate hydrolysis is described in relation to their rôle in signalling and tumorigenesis involving the Fhit protein, the human fragile histidine triad protein, which is a novel Ap3A binding/cleaving protein.

     

The control of chitin deposition by ecdysterone in larvae of Bombyx mori

The effect of ecdysterone on the deposition of chitin in Bombyx larvae was examined. The chitin content in the abdomen decreased following hormone treatment to a value half that of the controls. Studies with ¹⁴C-glucose revealed that whereas controls exhibited a gradual decrease in the rate of ¹⁴C-glucose incorporation into chitin, the administration of ecdysterone resulted in a rapid fall in the rate of incorporation followed by a rise until ecdysis occurred. Chitin catabolism was estimated at 0·11 mg chitin/hr, based on the chitin content and incorporation rates. A dual rôle is indicated for ecdysterone in chitin metabolism, namely the activation of both synthetic and lytic systems.     

Activity of faecal fluid of a leaf-cutting ant toward plant cell wall polysaccharides

The faecal fluid of the leaf-cutting ant, Atta colombica tonsipes, has been shown to contain enzymes active in the degradation of pectin, sodium polypectate, xylan, and carboxymethylcellulose. In addition, glycosidase activity has been detected in the faecal fluid using various naturally occurring disaccharides and synthetic p-nitrophenyl glycosides as substrates. The importance of these enzymes in the symbiosis between A. c. tonsipes and its food fungus is discussed, with particular emphasis on the rôle of the pectin-degrading enzymes.     

Interaction between glutathione and the endoplasmic reticulum in cyclic protein synthesis in sea urchin embryos.

Interaction between an oxidoreduction system and cyclic protein synthesis was studied in sea urchin embryos. When assayed enzymatically, in both in vivo and in vitro systems, the contents of GSH and GSSG varied inversely in a cyclic fashion. Diamide at 0.5 mM inhibited amino acid incorporation in not only the cyclic phase but also the basal phase, but 4-nitroquinoline-N-oxide at 1 μM inhibited only the cyclic phase. Sea urchin embryos contained membrane-bound ribosomes, and pulse-labeling with amino acids suggested that free ribosomes were responsible for the basal phase and membrane-bound ribosomes were responsible for the cyclic phase of amino acid incorporation. Thiol-disulfide interchanging enzyme was found in the endoplasmic reticulum fraction. An extract of the endoplasmic reticulm caused stimulation of binding of acetylphenylalanyl-tRNA to 40S ribosomes and polyphenylalanine synthesis in the presence of low GSH concentrations. An extract of the endoplasmic reticulum also catalyzed oxidoreduction from GSH to the KCl-soluble protein. Thus, the periodic stimulation of protein synthesis is interpreted to be the result of the periodic activation of membrane-bound ribosomes by the thiol-disulfide interchanging enzyme which accepts selectively the signal from the GSH cycle.     

Properties of cell-free extracts fromBacillus subtilis and its thermophilic mutant

After being heated at 65°C for 10 min, 51% of the protein in a cell-free extract fromBacillus subtilis BR151 was denatured, whereas the comparable value was 8% for the S-30 of a spontaneously occurring, temperature-resistant (T/r) mutant. Although ribosomes isolated from the T/r mutant retained 97% of their initial protein synthetic activity when preincubated at 60°C for 30 min, ribosomes prepared from the mesophilic parent were completely inactivated under these conditions. The optimum temperature for poly U-directed phenylalanine incorporation was 45°C for both parental and mutant extracts assayed in the absence of polyamines. The addition of spermidine to the S-30 from the mesophilic parent inhibited protein synthesis at each temperature tested, whereas this polyamine stimulated polyphenylalanine synthesis in the T/r extract at both 55°C and 65°C.     

The rôle of the suboesophageal ganglion in regulation of RNA synthesis in some insect tissues

The rôle of a factor produced by neurosecretory cells of the suboesophageal ganglion in the regulation of the level of RNA synthesis in some tissues of the female house cricket was studied in vivo and in vitro.It was shown that the action of the suboesophageal ganglion in vivo causes a reduction in the level of RNA synthesis in the neurosecretory cells of the pars intercerebralis, and also in the cells of the follicular epithelium, but it does not affect synthesis in the fat body cells.In experiments in which the action of the ganglion was examined in vitro, it was not found to have any influence on synthesis in the follicular epithelial cells, but the synthesis in the fat body cells was reduced. The causes of the differences obtained in the two types of experiments are discussed, and it is suggested that the suboesophageal ganglion acts directly on the fat body, but indirectly on the follicular epithelial cells through the corpora allata.     

Rôle of single amino acids in phagostimulation,growth, and survival of Acyrthosiphon pisum

Twelve amino acids and amides at 0·1 to 0·75 or 1·0% in 35% sucrose solution were individually tested for their rôle in phagostimulation, growth, and survival in Acyrthosiphon pisum. Leucine and phenylalanine were phagostimulatory at all concentrations tested, tryptophan and valine at 0·1, 0·2, and 0·5%, and threonine at 0·1% only. Methionine was reported earlier by us to be phagostimulatory at 0·05 to 0·5%. Histidine and isoleucine had no effect, whereas arginine and lysine HCl reduced uptake when compared to sucrose alone. The non-essential amino acids, canavanine sulphate and glutamine, reduced uptake at all concentrations, whereas homoserine was phagostimulatory at 0·1 and 0·75%.Arginine, canavanine sulphate, glutamine, histidine, homoserine, isoleucine, leucine, and valine increased weight and prolonged survival, whereas lysine HCl, phenylalanine, threonine, and tryptophan neither promoted growth nor increased survival. Radioactive leucine (¹⁴C(U)) was incorporated into the protein fraction of the larval body and exuviae indicating that it took part in protein synthesis. This seems to be the first report in insects where peptide or protein synthesis occurred from single amino acids in sucrose.