Development of insect resistance in tomato plants expressing the δ-endotoxin gene ofBacillus thuringiensis subsp.tenebrionis

A crystal 948.gif" alt="delta" align="BASELINE" BORDER="0">-endotoxin gene ofBacillus thuringiensis subsp.tenebrionis (B.t.t.) encoding a coleopteran insect-specific toxin was used to construct a chimeric gene which expressed the toxin in plant cells. Via anAgrobacterium tumefaciens binary vector system, the toxin gene was transferred into tomato cells. From leaf disks recombinant plants were regenerated. Hybridization experiments demonstrated that these plants synthesized toxin-specific mRNA of the expected size. Transgenic tomato plants with the chimericB.t.t. toxin gene contained a 74 kDa protein which cross-reacted with toxin antibodies. The expression caused a significant insecticidal activity of the transgenic tomato plants against Colorado potato beetle larvae.     

Biosynthesis of δ-aminolevulinic acid from glutamate by Sulfolobus solfataricus

The extremely thermophilic, obligately aerobic bacterium Sulfolobus solfataricus forms the tetrapyrrole precursor, 948.gif" alt="delta" align="BASELINE" BORDER="0">-aminolevulinic acid (ALA), from glutamate by the tRNA-dependent five-carbon pathway. This pathway has been previously shown to occur in plants, algae, and most prokaryotes with the exception of the -group of proteobacteria (purple bacteria). An alternative mode of ALA formation by condensation of glycine and succinyl-CoA occurs in animals, yeasts, fungi, and the -proteobacteria. Sulfolobus and several other thermophilic, sulfur-dependent bacteria, have been variously placed within a subgroup of archaea (archaebacteria) named crenarchaeotes, or have been proposed to comprise a distinct prokaryotic group designated eocytes. On the basis of ribosomal structure and certain other criteria, eocytes have been proposed as predecessors of the nuclear-cytoplasmic descent line of eukaryotes. Because aplastidic eukaryotes differ from most prokaryotes in their mode of ALA formation, and in view of the proposed affiliation of eocytes to eukaryotes, it was of interest to determine how eocytes form ALA. Sulfolobus extracts were able to incorporate label from [1-¹⁴C]glutamate, but not from [2-¹⁴C]glycine, into ALA. Glutamate incorporation was abolished by preincubation of the extract with RNase. Sulfolobus extracts contained glutamate-1-semialdehyde aminotransferase activity, which is indicative of the five-carbon pathway. Growth of Sulfolobus was inhibited by gabaculine, a mechanism-based inhibitor of glutamate-1-semialdehyde aminotransferase, an enzyme of the five-carbon ALA biosynthetic pathway. These results indicate that Sulfolobus uses the five-carbon pathway for ALA formation.Abbreviations AHA 4-amino-5-hexynoic acid - ALA 948.gif" alt="delta" align="BASELINE" BORDER="0">-aminolevulinic acid, Gabaculine, 3-amino-2,3-dihydrobenzoic acid - GSA glutamate 1-semialdehyde     

A break in the nitrogen cycle in aridlands? Evidence from δp15N of soils

We examined the content and isotopic composition of nitrogen within soils of a juniper woodland and found that a cryptobiotic crust composed of cyanobacteria, lichens, and mosses was the predominant source of nitrogen for this ecosystem. Disturbance of the crust has resulted in considerable spatial variability in soil nitrogen content and isotopic composition; intercanopy soils were significantly depleted in nitrogen and had greater abundance of ¹⁵N compared to intra-canopy soils. Variations in the ¹⁵N/¹⁴N ratio for inter- and intra-canopy locations followed similar Rayleigh distillation curves, indicating that the greater ¹⁵N/¹⁴N ratios for inter-canopy soils were due to relatively greater net nitrogen loss. Coverage of cryptobiotic crusts has been reduced by anthropogenic activities during the past century, and our results suggest that destruction of the cryptobiotic crust may ultimately result in ecosystem degradation through elimination of the predominant source of nitrogen input.     

Synaptosomal non-mitochondrial ATPase activities and drug treatment

Energy-using non-mitochondrial ATPases were assayed in rat cerebral cortex synaptosomes and synaptosomal subfractions, namely synaptosomal plasma membranes and synaptic vesicles. The following enzyme activities were evaluated: Na⁺, K⁺-ATPase; high- and low-affinity Ca²⁺-ATPase; basal Mg²⁺-ATPase; Ca²⁺, Mg²⁺-ATPase. The evaluations were performed after four week-treatment with saline [controls] or -adrenergic agents (948.gif" alt="delta" align="BASELINE" BORDER="0">-yohimbine, clonidine), energymetabolism interfering compound (theniloxazine), and oxygen-partial pressure increasing agent (almitrine), in order to define the plasticity and the selective changes in individual ATPases. In rat cerebral cortex, the enzyme adaptation to four-week-treatment with 948.gif" alt="delta" align="BASELINE" BORDER="0">-yohimbine or clonidine was characterized by increase in both high- and low-affinity Ca²⁺-ATPase activities. The action involves the enzyme form located in the synaptic plasma membranes. The enzyme adaptation to the subchronic treatments with theniloxazine or almitrine was characterized by increase in Na⁺, K⁺-ATPase or Mg²⁺-ATPase activities, respectively. The action involves the enzymatic forms located in the synaptic plasma membranes. Thus, the pharmacodynamic effects of the agents tested should also be related to the changes induced in the activity of some specific synaptosomal nonmitochondrial ATPases.     

Recognition of the Qa-2k tumor antigen by T cell receptor γ/δ of an immunopotentiator-induced tumoricidal T cell of mice

Tumor-specific expression of Qa-2^k antigen coded by the Q5^k gene on various mouse tumor cells and immunological response of the host mice to the antigen have been demonstrated [Seo et al. (1992) J Exp Med 175: 547; Tanino et al. (1992) Cancer Immunol Immunother 35: 230]. The possibility was examined that Qa-2 antigen is one of the recognition target molecules of immunopotentiator-induced, H-2-nonrestricted tumoricidal lymphocytes of Qa-2^– mice. Lymphocytes stimulated in vivo withP. acnes or culture-induced anomalous killers of B6.K1 mice did not exhibit significant in vitro cytotoxicity against B6.K1 lymphoblasts but lysed their Qa-2,3-congenic counterpart B6 lymphoblasts. To demonstrate the Qa-2 specificity of such cytotoxic cells more precisely, an L cell transformant clone (L^Q7b/Kb), which expressed the 1 and 2 domains of the Qa-2 antigen (Q7^b gene product), was generated by transfecting a cloned plasmid DNA containing a hybrid gene constructed from the 5 half of the Q7^b gene and the 3 half of the H-2K^b gene (pQ7^b/K^b). Using L^Q7b/Kb cells as the target cells and the nylon-wool-nonadherent fraction of lymphocytes fromP. acnes-stimulated (C3H/He × B6.K1)F1 mice (H-2^k, Qa-2^–) as the effector cells of the in vitro cytotoxicity reaction, the presence of cytotoxic cells that recognize the 1/2 region of the Q7^b gene product was demonstrated. The cytotoxic activity was dependent on T cells bearing T cell receptors of the /948.gif" alt="delta" align="BASELINE" BORDER="0"> type (TCR/948.gif" alt="delta" align="BASELINE" BORDER="0">). The (C3H/He × B6.K1)F1 effector cells, as well as the B6.K1 effector cells also lysed BW5147 lymphoma cells (Qa-2^k+) derived from AKR mice (Qa-2^–, H-2^k). By target-competition experiments it was shown that some of the effector cells lytic to BW5147 were identical to those that lysed L^Q7b/Kb. Therefore some of the tumoricidal cells induced by the immunopotentiator interact with the target tumor cells through recognition of the 1/2 region of the Qa-2^k tumor antigen by TCR/948.gif" alt="delta" align="BASELINE" BORDER="0">.     

Algae in mosquito breeding sites and the effectiveness of the mosquito larvicide Bacillus thuringiensis H-14

The presence of cyanobacteria generally decreased the effectiveness of Bacillus thuringiensis H-14 (BTI) as a mosquito larvicide. The effect was more pronounced when the mosquito larvae were exposed to BTI in the presence of several cyanobacterial strains. No synergistic or antagonistic effect between the 948.gif" alt="delta" align="BASELINE" BORDER="0">-endotoxin from BTI and the hepatotoxin from cyanobacteria was seen. Neurotoxic cyanobacterial strains caused very fast paralysis in mosquito larvae; the decreases in the effectiveness of BTI when tested in combination with a neurotoxic strain might be due to the effect of this paralytic action on the feeding rate of the mosquito larvae.     

Significance of betaines in the increased chlorophyll content of plants treated with seaweed extract

Seaweed extract, prepared by alkaline extraction of Ascophyllum nodosum (L.) Le Jol., applied either to the soil or to the foliage of tomato plants, produced leaves with higher chlorophyll levels than those of control plants. The effects on leaf chlorophyll content were investigated using a cucumber bioassay procedure devised for cytokinins. The seaweed extract was shown to increase the chlorophyll levels of the cucumber cotyledons, but ‘peaks’ of activity were obtained when widely different concentrations were used. The possibility that these effects were the result of betaines present in the extract was considered. Glycinebetaine, γ-aminobutyric acid betaine and δ-aminovaleric acid betaine all produced significantly enhanced chlorophyll concentrations in the cotyledons. ‘Peaks’ of activity were observed for each betaine: for glycinebetaine at 10⁻⁶ and between 10⁻⁴ and 10¹ mg 1⁻¹, for γ-aminobutyric acid betaine at 10⁻⁶, between 10⁻⁴ and 10⁻¹, and 10¹ mg 1⁻¹, and for δ-aminovaleric acid betaine between 10⁻⁵ and 10¹ mg 1⁻¹. It was concluded that the effects of enhancing chlorophyll levels produced by the seaweed extract were due, at least in part, to betaines.     

Nω-Hydroxyamino-α-amino acids as a new class of very strong inhibitors of arginases

 The effects of various compounds bearing an N-OH group such as N-hydroxy-guanidines, amidoximes, and hydroxylamines, on bovine and rat liver arginases was studied. Some of these compounds with an l-α-amino acid function at an appropriate distance from the N-OH group acted as strong competitive liver arginase inhibitors, displaying Ki values between 4 and 150 μM. Two compounds, N ^ε-hydroxy-l-lysine and N ^ω-hydroxy-d,l-indospicine, which exhibited Ki values of 4 and 20 μM (at pH 7.4), were the most potent inhibitors of arginase described to date. The distance between the α-amino acid and N-OH functions appeared to be crucial for potent inhibition of arginase, as N ^δ-hydroxy-l-ornithine, which has one -CH₂ group less than N ^ε-hydroxy-l-lysine, exhibited a 37-fold higher Ki value than N ^ε-hydroxy-l-lysine. Based on these results, a model for the interaction of N ^ω-hydroxyamino-l-α-amino acids with the arginase active site is proposed. This model involves the binding of the N-OH group of the inhibitors to the arginase Mn(II) center and suggests that N ^ε-hydroxy-l-lysine is a good transition state analog of arginase.