The effect of nucleosides on the induced synthesis of β-galactosidase in non-growing cells ofEscherichia coli

The induced synthesis of β-galactosidase in non-growing cells ofEscherichia coli starving for exogenous carbon and nitrogen sources was stimulated markedly by the addition of any of four nucleosides tested: adenosine, guanosine, cytidine, and uridine. Adenosine was used as a representative of this group of compounds in most experiments. The decrease of ability of the cells to synthesize β-galactosidase, resulting from a prolonged starvation for exogenous carbon and nitrogen, was removed by adenosine. This compound also considerably reduced the inhibitory effect of metabolic poisons on the induced synthesis of β-galactosidase. The blockade of induced β-galactosidase synthesis evoked in aerobically grown cells by anaerobic starvation for exogenous sources of carbon and nitrogen was also significantly reduced by adenosine. The weak transient catabolic repression of induced synthesis of β-galactosidase evoked by glucose in non-growing cells ofEscherichia coli deprived of exogenous carbon and nitrogen sources was prevented by adenosine. The total repression caused by higher glucose concentrations was not influenced by this compound. The results are discussed from the point of view of the role of the energy state ofEscherichia coli cells in the regulation of β-galactosidase synthesis.     

Effect of ethionine on the synthesis of β-galactosidase inEscherichia coli

Ethionine at concentrations of 10⁻³M, 5×10⁻³M and 10⁻²M inhibits growth, both of β-galactosidase inducible ML-30 and constitutive ML-308Escherichia coli strains. The protein synthesis (measured by the incorporation of l-leucine-¹⁴C and l-aspartic-¹⁴C acid into proteins) of these strains is inhibited to the same extent as their growth. The synthesis of inducible and constitutive β-galactosidase produced by the strains ML-30 and ML-308, respectively, is considerably inhibited by ethionine.     

Spores of microorganisms

6-Azauracil at a concentration of 1 μmole/ml inhibits by 50% the outgrowth of germinated spores of a strain ofBacillus cereus, concentration of 1.5 μmole/ml resulting in 100% inhibition. Two distinct maxima of sensitivity to 6-azauracil are observed during postgerminative development of spores. The first occurs during early stages of development (immediately after depolymerization period) and the second after about 60 min of cultivation (late stage of swelling). Uracil reverses the inhibition of the outgrowth of spores caused by 6-azauracil when added during 0–30 min of the spore development. The addition of uracil after 30 min of the germination does not bring about the reversion of the effect of 6-azauracil. An important role of pyrimidine pathway via orotidine 5′-phosphate in germinating spores was proved, suggesting a possible use of 6-azauracil in synchronization of the postgerminative development of spores.     

倭竹属地理分布的研究

倭竹属Shibataea Makino隶于禾本科之竹亚科,现已知有8种,分布于我国东南部的浙江、福建、江苏、安徽、江西等省,广东、台湾两省有少量栽培,日本产1种。苏联、西德、印尼等国所栽培的倭竹均系自我国或日本引入。我国浙-闽地区产8种,且都有野生发现,是本属的现代分布中心。倭竹属植物体型矮小,常植于庭院或公园中供观赏。近年来盆景艺术迅速发展,微型园林日益兴起,倭竹属植物体态优美,常绿,耐寒且易于栽培,为广大园林工作者所垂青。     

Production of a foreign protein product with genetically modified plant cells.

Plant cells (Nicotiana tabacum) were genetically engineered to produce a foreign protein, chloramphenicol acetyltransferase (CAT), and the CAT production from suspension cultures was investigated. Suspension cultures were grown in a shake flask, a stirred fermenter, and a bubble-column fermenter. The CAT production was growth related and the maximum activity was reached during the early stationary phase. A 41-day, semicontinuous stirred fermenter run, consisting of five sequential batch runs, demonstrated long-term CAT production. Continuous CAT production was also accomplished in a bubble-column fermenter at a medium flow rate of 3.1 ml h-1, which was equivalent to a dilution rate of 0.25 day-1.     

Nucleotide sequence of the sex pheromone inhibitor (iAD1) determinant of Enterococcus faecalis conjugative plasmid pAD1

The determinant for the peptide sex pheromone inhibitor iAD1 (iad) on the hemolysin/bacteriocin plasmid pAD1 of Enterococcus faecalis was sequenced. The sequence reveals a 22-amino-acid precursor with the carboxyl-terminal 8 residues corresponding to iAD1. It appears that iAD1 is a component of its own signal sequence.     

Identification of four novel splice site mutations in the ornithine transcarbamylase gene

Ornithine transcarbamylase (OTC) deficiency, the most common inborn error of the urea cycle, shows X-linked inheritance with frequent new mutations. Using polymerase chain reaction (PCR) amplification of the individual exons including adjacent intron sequences followed by direct sequencing of the amplimers we identified four new mutations affecting donor splice sites of introns 2, 5, 6, and 8. The mutation at the first position of intron 2 was a G to A exchange associated with acute neonatal hyperammonemia in a male patient at the age of 5 months. A G to C substitution in intron 5 was detected in a boy who developed 2 days after birth hypotonia, and respiratory distress, followed by severe hyperammonemia and terminal coma. The intron 6 mutation, a G to T substitution, was detected in a girl presenting with first episodes of vomiting and agitation at the age of 2 months. The mutation in intron 8, also a G to T transition, caused fatal hyperammonemia and early death at the age of 15 days in a male patient. We present four donor splice site mutations resulting in severe neonatal or very early onset of the disease in three boys and in one female patient. As the GT dinucleotide of the 5 donor splice site is invariant and required for correct splicing the described mutations may lead to improperly spliced mRNAs and aberrant gene products.     

Agrobacterium-mediated transformation of apple (Malus x domestica Borkh.): an assessment of factors affecting regeneration of transgenic plants

We have previously developed a protocol for efficient gene transfer and regeneration of transgenic calli following cocultivation of apple (cv. Jonagold) explants with Agrobacterium tumefaciens (De Bondt et al. 1994, Plant Cell Reports 13: 587–593). Now we report on the optimization of postcultivation conditions for efficient and reproducible regeneration of transgenic shoots from the apple cultivar Jonagold. Factors which were found to be essential for efficient shoot regeneration were the use of gelrite as a gelling agent and the use of the cytokinin-mimicing thidiazuron in the selective postcultivation medium. Improved transformation efficiencies were obtained by combining the hormones thidiazuron and zeatin and by using leaf explants from in vitro grown shoots not older than 4 weeks after multiplication. Attempts to use phosphinothricin acetyl transferase as a selectable marker were not successful. Using selection on kanamycin under optimal postcultivation conditions, about 2% of the leaf explants developed transgenic shoots or shoot clusters. The presence and expression of the transferred genes was verified by -glucuronidase assays and Southern analysis. The transformation procedure has also been succesfully applied to several other apple cultivars.Abbreviations BAP benzylaminopurine - CTAB hexadecyltrimethylammoniumbromide - Na₂EDTA ethylenediamine-tetra-acetate ferric-sodium salt - FeNaEDTA ethylenediamine-tetra-acetate ferric-sodium salt - GA₃ gibberellic acid 3 - GusA -glucuronidase - gusA -glucuronidase gene of Escherichia coli - IAA indole acetic acid - IBA indole butyric acid - 2iP N6-2-isopentenyl adenine - NAA naphthalene acetic acid - nptII neomycinphosphotransferase II gene - bar phosphinothricin acetyl transferase gene - PCR polymerase chain reaction - PPT phosphinothricin - STS silver thiosulphate - T-DNA transferred DNA - TDZ thidiazuron - X-Gluc 5-bromo-4-chloro-3-indolyl -D-glucuronide - Zea trans-Zeatin     

Partial auxin deprivation affects endogenous cytokinins in an auxin-dependent,cytokinin-independent tobacco cell strain

The dynamics of individual endogenous cytokinins within the growth cycle (subculture interval) of an auxin-dependent and cytokinin-independent cell suspension culture ofNicotiana tabacum L. (strain VBI-0) were determined using high performance liquid chromatography and radioimmunoassay. In cells grown at an optimum auxin concentration the transient maxima of N⁶-(²-isopentenyl)adenine and N⁶-(²-isopentenyl)-adenosine correlated with the onset of cell division. Cultivation of the cells in a partially auxin-deprived medium resulted in ca. tenfold increase of all endogenous cytokinins. A very distinct maximum of N⁶-(²-sopentenyl) adenine appeared at the beginning of subculture. This indicates that a lack of auxin induced an accumulation of cytokinins predominantly in the form of the free bases, which are physiologically more active than the corresponding ribosides.Abbreviations iP N⁶-(²-isopentenyl)adenine - [9R]iP N⁶-(²-isopentenyl)adenosine - t-Z trans-zeatin - t-[9R]Z trans-zeatin riboside - IAA indole-3-acetic acid - NAA 1-naphthaleneacetic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - f.w. fresh weight - SBI subculture interval - C complete medium - PAD partially auxin-deprived medium - RP-HPLC reverse phase high performance liquid chromatography - RIA radioimmunoassay - PAL L-phenylalanine ammonia lyase