Expression of three rare fragile sites: chromosomal truncation, amplification of distal segment and telomeric renewal

Fluorescence in situ hybridization with a telomeric probe was used to monitor telomeric renewal following breakage induced by the rare fragile sites FRA10A, FRA12A and FRA16B. Interstitial telomere-like sequences were detected only at the break sites of FRA10A. Received: 26 February 1977; in revised form: 14 August 1997 / Accepted: 22 August 1997     

Models for the molybdenum hydroxylases

 This commentary reviews structural, spectroscopic, and chemical models for the molybdenum hydroxylases. It briefly describes the current state of modeling and identifies areas where model chemistry may play a future role in understanding these enzymes. Received: 28 April 1997 / Accepted: 20 August 1997     

Microsatellite fingerprinting in lettuce (Lactuca sativa L.) and wild relatives

Southern hybridisation with a single microsatellite probe, (TCT)₁₀, sufficed to discriminate between a representative set of cultivars/accessions of lettuce, Lactuca sativa L., and its wild relatives L. serriola, L. saligna and L. virosa. Variability within cultivars was tested in a relatively modern cultivar (Hector), where no variation was found, and in an older and morphologically more variable cultivar (Madrilene), where heterogeneity was observed in the TCT fingerprint. (TCT)₁₀ fingerprinting should be useful for variety identification and homogeneity testing in lettuce. Received: 25 July 1997 / Revision received: 5 August 1997 / Accepted: 30 August 1997     

Stable production of human gastric lipase by chromosomal integration in the fission yeast Schizosaccharomyces pombe

Strains of the fission yeast Schizosaccharomyces pombe have been constructed containing single or multiple chromosomally integrated copies of an expression cassette for production of human gastric lipase. Integrant strains of S. pombe secrete active lipase and are stable for lipase production over a minimum of 50 generations in non-selective media. Lipase activity levels for integrant strains containing up to three tandem copies of the expression cassette are strongly correlated with copy number of the cassette in both complete and minimal media. Lipase activity is higher in complete medium than in minimal medium. Strains carrying three chromosomally integrated expression cassette copies can be grown without selection in complete medium and are capable of significantly higher lipase activities than strains containing the expression cassette on a multicopy plasmid. Received: 27 March 1997 / Received revision: 13 August 1997 / Accepted: 25 August 1997     

A repetitive DNA sequence common to the different B chromosomes of the genus Brachycome

Dot-like micro B chromosomes of Brachycome dichromosomatica were analysed for their sequence composition. Southern hybridization patterns of a total micro B probe to genomic DNA from plants with and without micro Bs demonstrated that the micro Bs shared sequences with the A chromosomes. In addition to telomere, rDNA and common A and B chromosome sequences, a new B-specific, highly methylated tandem repeat (Bdm29) was detected. After in situ hybridization with Bdm29 the entire micro B chromosome was labelled and clustering of the condensed micro Bs could be observed at interphase. A high number of Bdm29-like sequences were also found in the larger B chromosomes of B. dichromosomatica and in other Bs within the genus Brachycome. Received: 30 May 1997; in revised form: 20 August 1997 / Accepted: 20 August 1997     

Conversion of Lysine to L-Pipecolic Acid Induces Flowering in Lemna paucicostata 151

The natural occurrence of L-pipecolic acid and conversion oflysine to L-pipecolic acid in Lemna paucicostata 151 were demonstrateddefinitively by GC-MS. The strong flower-inducing activity ofL-pipecolic acid has already been demonstrated. Thus, the presentstudy indicates that the effect of lysine on flowering is mediatedby L-pipecolic acid. (Received June 30, 1997; Accepted August 22, 1997)     

Determining the sex of Antarctic krill Euphausia superba using carapace measurements

A discriminant function using simple carapace measurements corretly determined the sex of 87% of male and 89% of female Antarctic krill Euphausia superba. This facilitated the use of sex-specific regression models which increased the accuracy of total length estimates. Received: 5 May 1997 / Accepted: 30 August 1997     

Light induced states in MbCO denatured with Guanidine hydrochloride

We present the results of a comparative study of the binding of carbon monoxide to myoglobin in glycerol/buffer solution with different concentrations of guanidine hydrochloride, under extended illumination over the temperature range 30 – 80 K. The changes in the Soret band indicate that the folding state of the protein is a key parameter in determining the photodissociation process and the relaxation rate of the protein. Received: 30 January 1997 / Accepted: 14 August 1997     

HABITAT AND DIET OF EARLY STAGES OF SEPIA OFFICINALIS L. (CEPHALOPODA) IN MORBIHAN BAY, FRANCE

The nursery grounds of Sepia officinalis were identified inthe Gulf of Morbihan, on the Atlantic coast of France, and theirabiotic and biotic features described. From the measurementof the young cuttlefish captured, their growth and developmentcould be followed through a period of five months. Analysisof the stomach contents of the cuttlefish and identificationof the prey consumed gave a measure of their feeding activityand diet. The young animals were concentrated in the two parts(East and West) of Morbihan Bay. These were distinguished bydifferent sediments (sandy-mud in the East and sand with shell-debrisin the West) and by water temperature (higher in the East whichallow a greater growth of the young cuttlefish). These sitesare rich in crustaceans Amphipoda, Brachyura and Macrura whichcompose the diet of young cuttlefish. Fish (Gobiidae and Syngnathidae)appear in the diet from August. The feeding activity of thecuttlefish (given by the repletion quotient) increased fromJune to August reaching about 80% in both parts of the Bay.It decreased to nearly 50% in September and October. (Received 11 February 1997; accepted 25 August 1997)     

The mutational-response index and codon bias in genes from a Frankia nif operon

 The mutational response index (MRI) and measurements of codon bias were determined in three characterised genes, and two open reading frames of unknown function, from the Frankia nif operon, which encodes genes for nitrogen fixation. The merits of the different systems of measuring codon usage are discussed in the light of the results, as are the applicability of these techniques to the assessment of the translational function of putative open reading frames. Received: 8 August 1997 / Accepted: 19 September 1997     

Embryogenesis and plant regeneration from callus cultures derived from unpollinated ovaries of Hyoscyamus muticus L.

Unpollinated ovaries of Hyoscyamus muticus L. (commonly known as Egyptian henbane) were cultured on Murashige and Skoog and Bourgin and Nitsch media supplemented with various growth hormones to study the organogenesis, embryogenesis and regeneration of plantlets. Embryogenesis was reported for callus grown on both media containing 0.05 mg/l α-naphthaleneacetic acid and 0.5 mg/l 6-benzylaminopurine. Differentiation of roots and shoots from the calli also occurred in these media. Albinism or chlorophyll deficiency and variation in ploidy level were observed among the ovary-derived plantlets. Received: 7 April 1997 / Revised received: 2 August 1997 / Accepted: 2 September 1997     

Optimization of fermentation conditions for the production of ethylene-diamine-disuccinic acid by Amycolatopsis orientalis

The production of EDDS (ethylene-diamine-disuccinic acid), a potential substitute for EDTA, has been optimized up to a product concentration of 20 grams per litre in fermentations of Amycolatopsis orientalis. Decisive steps for the increase in productivity were variation of the synthetic medium composition, investigation of the influence of metal ions on product formation, controlled feeding of carbon and nitrogen sources in fed-batch fermentations and improvement of the downstream processing steps. Received 05 May 1997/ Accepted in revised form 13 August 1997     

Dense aggregations of tube-building polychaetes: response to small-scale disturbances

Many species of tube-building polychaetes form dense aggregations or ‘patches’ within marine soft-bottom habitats. Although the ecological importance of such patches has been well studied, the effect of small-scale disturbances within patches has not been investigated. On the intertidal sandflat Drum Sands, Firth of Forth, Scotland, the tube-building spionid Pygospio elegans Claparède forms patches approximately 1-1.5 m², wherein its density is significantly greater than in surrounding sediments. This study explicitly investigates whether the initial communities colonising small-scale disturbances within P. elegans patches differ in terms of community structure and colonisation mode from those of surrounding sediments.Defaunated sediments (1/125 m²) were implanted into the sediments within and outside patches during April, August and December 1997, and sampled after 3 weeks. The results indicated that some species colonised patches and non-patches in significantly different numbers, at least at certain times of the year. Following these controlled disturbances, P. elegans larvae colonised patches in significantly higher numbers compared to non-patch areas during April 1997, but showed the opposite trend in August 1997 when larval recruitment was relatively low. Adult P. elegans colonised patch sediments in higher numbers than non-patch ones during August and December. Capitella capitata (Fabricius) consistently colonised all defaunated areas in relatively high numbers while Cerastoderma edule (L.) and Macoma balthica (L.) colonised non-patch azoic sediments in significantly higher numbers than patch azoics during April 1997. Multivariate analyses, together with nonparametric analysis of similarities (ANOSIM) tests, revealed that the community composition of the disturbed sediments was significantly different between patches and non-patches during April 1997 only. These analyses also indicated that there was a strong temporal effect on community composition since the April community was markedly different from those of August and December 1997. Sediment measurements taken during December suggested that the observed faunal differences were unlikely to have been a response to differences in bulk sediment characteristics or redox potential.It is proposed that the initial recolonisation differences were likely to have been due to the near-bed hydrodynamic effects of P. elegans tubes creating local sediment stabilisation. The ecological implications of differential recruitment following small-scale disturbances within patches compared to outside patches are discussed. The ability of P. elegans patches to enhance successful conspecific colonisation, as demonstrated here, may explain the longevity of such patches. Their persistence promotes alpha diversity and small-scale patchiness, together with providing a local source of colonists for the initial recovery of large-scale disturbances.     

Influence of acetic acid on the growth of Escherichia coli K12 during high-cell-density cultivation in a dialysis reactor

High-cell-density cultivations of Escherichia coli K12 in a dialysis reactor with controlled levels of dissolved oxygen were carried out with different carbon sources: glucose and glycerol. Extremely high cell concentrations of 190 g/l and 180 g/l dry cell weight were obtained in glucose medium and in glycerol medium respectively. Different behaviour was observed in the formation of acetic acid in these cultivations. In glucose medium, acetic acid was formed during the earlier phase of cultivation. However, in glycerol medium, acetic acid formation started later and was particularly rapid at the end of the cultivation. In order to estimate the influence of acetic acid during these high-cell-density cultivations, the inhibitory effect of acetic acid on cell growth was investigated under different culture conditions. It was found that the inhibition of cell growth by acetic acid in the fermentor was much less than that in a shaker culture. On the basis of the results obtained in these investigations of the inhibitory effect of acetic acid, and the mathematical predictions of cell growth in a dialysis reactor, the influence of acetic acid on high-cell-density cultivation is discussed. Received: 20 May 1997 / Received revision: 12 August 1997 / Accepted: 25 August 1997     

Regulation of lysine ɛ-aminotransferase by carbon source and lack of control by phosphate in Streptomyces clavuligerus

Cephalosporin production by Streptomyces clavuligerus is known to be negatively regulated by carbon sources, e.g., glycerol and starch, and by phosphate at high concentrations. Formation of lysine ɛ-aminotransferase (LAT) activity, the first enzyme of the biosynthetic pathway, was affected by a high concentration of carbon source. Whereas 3% starch more than doubled LAT activity production as compared to 1% starch, 3% glycerol repressed LAT activity formation by 20%–30%. LAT activity production was not affected by 100 mM K₂HPO₄. Our results thus show that the negative effects of 2% glycerol and 3% starch and 100 mM phosphate on cephalosporin production are not due to an effect on production of LAT activity. However, repression of LAT activity by 3% glycerol would be expected to play a negative role in antibiotic production. Received: 13 June 1997 / Received revision: 20 August 1997 / Accepted: 25 August 1997     

Biolistic transfer and expression of a uidA reporter gene in different tissues of Allium sativum L.

The biolistic particle delivery system was used to transfer the uidA gene into different garlic tissues, including regenerable calli. These tissues showed a high endogenous nuclease activity preventing exogenous DNA expression. After submerging the tissues for 24 h in a 2 mm solution of the nuclease inhibitor aurintricarboxylic acid, transient expression of the uidA gene was detected. Furthermore, vacuum infiltration of aurintricarboxylic acid into the garlic tissues significantly increased the percentage of explants showing transient expression. Among four plasmids tested, pDE4 containing the CaMV35S-uidA construct produced the best results. Received: 16 May 1997 / Revision received: 26 August 1997 / Accepted: 25 September 1997     

Plant regeneration via somatic embryogenesis in pigeonpea (Cajanus cajan L. Millsp)

Efficient plant regeneration via somatic embryogenesis has been developed in pigeonpea. Cotyledon and leaf explants from 10-day-old seedlings produced embryogenic callus and somatic embryos when cultured on Murashige and Skoog (MS) medium supplemented with 10 μm thidiazuron (TDZ). Subsequent withdrawal of TDZ from the induction medium resulted in the maturation and growth of the embryos into plantlets on MS basal medium. The rooted plantlets were transferred and acclimatized on vermiculite where they showed normal morphological characters. Received: 23 December 1996 / Revision received: 22 July 1997 / Accepted: 2 August 1997     

Purification and characterization of recombinant spider silk expressed in Escherichia coli

A partial cDNA clone, from the 3′ end of the dragline silk gene was isolated from Nephila clavipes major ampullate glands. This clone contains a 1.7-kb insert, consisting of a repetitive coding region of 1.4-kb and a 0.3-kb nonrepetitive coding region; 1.5-kb of the 1.7-kb fragment was cloned into Escherichia coli and a␣43-kDa recombinant silk protein was expressed. Characterization of the purified protein by Western blot, amino acid composition analysis, and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry confirms it to be spider dragline silk. Received: 7 April 1997 / Received revision: 24 July 1997 / Accepted: 25 August 1997     

Enantioselective hydration of 2-arylpropionitriles by a nitrile hydratase from Agrobacterium tumefaciens strain d3

The enantioselective nitrile hydratase from the bacterium Agrobacterium tumefaciens d3 was purified and completely separated from the amidase activity that is also present in cell extracts prepared from this strain. The nitrile hydratase had an activity optimum at pH 7.0 and a temperature optimum of 40 °C. The holoenzyme had a molecular mass of 69 kDa, the subunits a molecular mass of 27 kDa. The enzyme hydrated various 2-arylpropionitriles and other aromatic and heterocyclic nitriles. With racemic 2-phenylpropionitrile, 2-phenylbutyronitrile, 2-(4-chlorophenyl)propionitrile, 2-(4-methoxy)propionitrile or ketoprofen nitrile the corresponding (S)-amides were formed enantioselectively. The highest enantiomeric excesses (ee >90% until about 30% of the respective substrates were converted) were found for the amides formed from 2-phenylpropionitrile, 2-phenylbutyronitrile and ketoprofen nitrile. For the reaction of the purified nitrile hydratase, higher ee values were found than when whole cells were used in the presence of an inhibitor of the amidase activity. The enantioselectivity of the whole-cell reaction was enhanced by increasing the reaction temperature. Received: 20 June 1997 / Received revision: 28 August 1997 / Accepted: 29 August 1997     

Immunocytochemical visualization of the centromeres during male and female meiosis in Lilium longiflorum

Immunofluorescence staining with an antiserum raised against a presumptive meiotic histone, which has been shown to appear prior to male meiosis in liliaceous plants, preferentially stained the centromere (kinetochore) region of meiotic chromosomes in microsporocytes and megasporocytes. Using this antiserum, we were able clearly to visualize the centromeres at all important meiotic stages in microsporocytes, namely, the association and fusion of centromeres of homologous chromosomes at zygotene-pachytene in prophase I, the disjunction of the homologous centromeres at diplotene, the doubling of each centromere at metaphase I and nonseparation of the sister centromeres at anaphase I, by confocal laser scanning microscopy. Thus, this report provides a complete picture of the behavior of centromeres during meiosis in a eukaryote for the first time. This antiserum also decorated centromeres during female meiosis in cryo-sectioned megasporocytes, but did not stain the centromeres of mitotic chromosomes in root-tip meristem. From these observations, it is suggested that a meiosis-specific centromere protein is required for the meiosis-specific behavior of the centromere. Received: 12 May 1997; in revised form: 20 August 1997 / Accepted: 25 August 1997