Showing papers by "Leibniz Association published in 1996"

The relationships between the dwarfing genes of wheat and rye

Abstract: The improvement of lodging resistance by introducing major dwarfing genes, classified either as GA insensitive or GA sensitive, is one of the main strategies chosen by cereal breeders. In the present paper the current knowledge about the genetics, chromosomal localisation and the homoeoallelic relationships of the dwarfing genes in wheat and rye is reviewed. The confusing system of the symbolisation of the GA insensitive dwarfing genes/alleles in wheat is discussed and a nomenclature based on rules for gene symbolisation in wheat is proposed.

Proteases and proteolytic cleavage of storage proteins in developing and germinating dicotyledonous seeds

Abstract: Proteolytic cleavage plays an important role in storage protein deposition and reactivation in seeds. Precursor polypeptides are processed by limited proteolysis to mature subunits of reserve proteins in storage tissue cells of developing seeds. Steps of proteolytic processing are closely related to steps in intracellular protein transfer through the endomembrane system and to the deposition in the storage vacuole. In germinating seeds special endopeptidases trigger storage protein breakdown by limited proteolysis. The induced conformation changes of storage proteins open them to attack by additional endo- and exopeptidases which degrade the protein reserves completely. Proteases that catalyse limited cleavage or complete degradation are synthesized as precursors which also undergo stepwise limited proteolysis when they are formed in cotyledons of developing or germinating seeds. In general, this processing transforms enzymatically inactive proenzymes into active proteases. Different compartments participate in the processing steps. Many of the proteases are encoded by small multigene families. Different members of the corresponding protease families seem to act during seed development and germination. Proteolytic processes that contribute to the molecular maturation and to the reactivation of storage proteins in dicotyledonous seeds seem to be controlled by (1) differential expression of members of the protease-encoding gene families ; (2) stepwise processing and activation of protease precursor polypeptides ; (3) transient differential compartmentation of precursors and mature polypeptides of proteases and storage proteins, respectively ; and (4) interacting changes in storage protein structure and protease action. The present knowledge on these processes is reviewed.

Estimating genetic erosion in landraces — two case studies

Abstract: The results of collecting missions in Albania in 1941 and 1993 and in South Italy in 1950 and in the eighties allowed a comparison to be made of the material cultivated. The number of landraces still cultivated recently, as compared to their former number, was the basis for the estimation of genetic erosion. Genetic erosion (GE) was calculated as GE=100%-GI (Genetic integrity). Genetic erosion was found to be 72.4% in Albania and 72.8% in South Italy, respectively. These results prove the high degree of genetic erosion in landraces from different parts of the Mediterranean area. Apart from the economic conditions, several other factors are responsible for genetic erosion, among them breeding system, crop type (i.e., garden or field crop) and crop group (e.g., cereals, vegetables and pulses). The results show that in the areas investigated there are still landraces for in situ conservation. Ex situ conservation in genebanks proved to be a possibility. An integration process is necessary to prevent losses in crops which are difficult to propagate under ex situ conditions. The complementarity of both conservation methods is stressed.

Aerosol number size distributions from 3 to 500 nm diameter in the arctic marine boundary layer during summer and autumn

Abstract: Aerosol physics measurements made onboard the Swedish icebreaker Oden in the late Summer and early Autumn of 1991 during the International Arctic Ocean Expedition (IAOE-91) have provided the first data on the size distribution of particles in the Arctic marine boundary layer (MBL) that cover both the number and mass modes of the size range from 3 to 500 nm diameter. These measurements were made in conjunction with atmospheric gas and condensed phase chemistry measurements in an effort to understand a part of the ocean-atmosphere sulphur cycle. Analysis of the particle physics data showed that there were three distinct number modes in the submicrometric aerosol in the Arctic MBL. These modes had geometric mean diameters of around 170 nm, 45 nm and 14 nm referred to as accumulation, Aitken and ultrafine modes, respectively. There were clear minima in number concentrations between the modes that appeared at 20–30 nm and at 80–100 nm. The total number concentration was most frequently between 30 and 60 particles cm −3 with a mean value of around 100 particles cm −3 , but the hourly average concentration varied over two to three orders of magnitude during the 70 days of the expedition. On average, the highest concentration was in the accumulation mode that contained about 45% of the total number, while the Aitken mode contained about 40%. The greatest variability was in the ultrafine mode concentration which is indicative of active, nearby sources (nucleation from the gas phase) and sinks; the Aitken and accumulation mode concentrations were much less variable. The ultrafine mode was observed about two thirds of the time and was dominant 10% of the time. A detailed description and statistical analysis of the modal aerosol parameters is presented here. DOI: 10.1034/j.1600-0889.1996.t01-1-00005.x

Occurrence of an ultrafine particle mode less than 20 nm in diameter in the marine boundary layer during Arctic summer and autumn

Abstract: The International Arctic Ocean Expedition 1991 (IAOE-91) provided a platform to study the occurrence and size distributions of ultrafine particles in the marine boundary layer (MBL) during Arctic summer and autumn. Measurements of both aerosol physics, and gas/particulate chemistry were taken aboard the Swedish icebreaker Oden. Three separate submicron aerosol modes were found: an ultrafine mode ( D p 100 nm). We evaluated correlations between ultrafine particle number concentrations and mean diameter with the entire measured physical, chemical, and meteorological data set. Multivariate statistical methods were then used to make these comparisons. A principal component (PC) analysis indicated that the observed variation in the data could be explained by the influence from several types of air masses. These were characterised by contributions from the open sea or sources from the surrounding continents and islands. A partial least square (PLS) regression of the ultrafine particle concentration was also used. These results implied that the ultrafine particles were produced above or in upper layers of the MBL and mixed downwards. There were also indications that the open sea acted as a source of the precursors for ultrafine particle production. No anti-correlation was found between the ultrafine and accumulation particle number concentrations, thus indicating that the sources were in separate air masses. DOI: 10.1034/j.1600-0889.1996.t01-1-00006.x

Seasonal spermatogenesis and testosterone production in roe deer (Capreolus capreolus)

Abstract: Quantitative changes in testes of roe deer were studied during the annual cycle. Testicular spermatozoa were counted and proportions of different cell types were estimated using DNA flow cytometry. A proliferation-specific antigen of somatic cells was evaluated by an immunoradiometric assay. Apoptosis was examined by cell death detection ELISA, and testosterone concentrations were measured with an enzymeimmunoassay. The testis mass of adults reached a maximum during the rut from mid-July to mid-August. Gonadal size corresponded to numbers of testicular spermatozoa g-1 testis. In the rutting period, epididymal spermatozoa were of the highest morphological and functional competence. The proportions of haploid (1c), diploid (2c) and tetraploid (4c) cells changed over time with the maximum of 1c cells during the breeding period. Meiotic division (1c:4c ratio) increased sharply immediately before rut, while mitosis (% cells in G2-M phase) was already high during spring. Proliferation and apoptosis revealed an opposite pattern during the annual cycle; the most intensive apoptosis occurred during the time of testis involution. Testosterone production showed a biphasic pattern. It dropped rapidly from the highest value in August to very low concentrations thereafter. Yearlings were characterized by smaller peaks of testicular growth and sperm production. Fawns started testicular growth and meiosis in winter. In conclusion, the production of spermatozoa in roe deer is intensified by enlargement of gonads as well as enhanced efficiency of spermatogenesis during the rut. Interrupted proliferation and stimulated apoptosis promote testis involution after the rut, and testosterone seems to play a role in the regulation of both processes.

The Ty1-copia group retrotransposons of Allium cepa are distributed throughout the chromosomes but are enriched in the terminal heterochromatin.

Abstract: The genomic organization and diversity of the Ty1-copia group retrotransposons has been investigated in a monocotyledonous plant, Allium cepa. We used the polymerase chain reaction (PCR) to generate sequences corresponding to a conserved domain of the reverse transcriptase gene of Ty1-copia retrotransposons in this plant. Sequence analysis of 27 of these PCR products shows that they are a highly heterogeneous population, a feature which is common in plants but not in yeast and Drosophila. Slot-blot analysis shows there are 100,000-200,000 copies of Ty1-copia group retrotransposons within the A. cepa genome (2C = 31.7 pg), indicating that they are a significant component of the genome of this plant. In situ hybridization to metaphase chromosomes reveals that Ty1-copia retrotransposons are distributed throughout the euchromatin of all chromosomes of A. cepa but are enriched in the terminal heterochromatic regions, which contain tandem arrays of satellite sequences. This is the first clear evidence for the presence of Ty1-copia retrotransposons in the terminal heterochromatin of plants and contrasts with the distribution of these elements in other plant species.

Developmental and tissue-specific expression of JIP-23, a jasmonate-inducible protein of barley

Abstract: Developmental expression of a 23 kDa jasmonate-induced protein (JIP-23) of barley leaves (Hordeum vulgare cv. Salome) was studied by measuring the time-dependent accumulation of transcript and protein during germination. Tissue-specific expression of JIP-23 was analyzed immunocytochemically and by in situ hybridizations, respectively. During seed germination JIP-23 mRNA was found to accumulate transiently with a maximum at 32 h, whereas the protein was steadily detectable after the onset of expression. The occurrence of new isoforms of JIP-23 during germination in comparison to jasmonate-treated leaves suggests, that the JIP-23 gene family of barley is able to express different subsets of isoforms dependent on the developmental stage. JIP-23 and its transcript were found mainly in the scutellum, the scutellar nodule and in lower parts of the primary leaf of 6 days old seedings. All these tissues exhibited high levels of endogenous jasmonates. In situ hybridization revealed specific accumulation of JIP-23 mRNA in companion cells of the phloem in the nodule plate of the scutellum. In accordance with that, JIP-23 was detected immunocytochemically in phloem cells of the root as well as of the scutellar nodule and in parenchymatic cells of the scutellum. The cell type-specific occurrence of JIP-23 was restricted to cells, which are known to be highly stressed osmotically by active solute transport. This observation suggests, that the expression of this protein might be a response to osmotic stress during development.

Influence of an optimized interphase on the properties of polypropylene/glass fibre composites

Abstract: To ensure efficient transfer of stress between glass fibres and polypropylene (PP) matrix, the fibres are sized and the matrix is chemically modified. In this study, the interphase properties of glass fibre/PP model composites have been investigated using fibres sized with γ-aminopropyltriethoxysilane (A1100) and various polymer dispersions (polyethylene/polyurethane (PE/PUR). PP, PP/PUR and epoxy) and unmodified (PP) or modified (PPM) matrices. The acid-base properties of the fibre surface were characterized by zeta potential measurements in electrolyte solutions with varying pH. Fibre-melt interaction was characterized by direct wetting measurements of polymer melts on fibre surfaces and single-fibre pull-out tests under conditions comparable to processing conditions. Composite mechanical properties influenced by fibre—melt interaction were tested using continuous fibre-reinforced polypropylenes. The direct fibre—melt wetting experiments provided evidence for acid—base interactions together with interdiffusion effects in the interphase between sized glass fibres and the modified polypropylene matrix or physical interactions at the fibre—polymer melt interface. It was proved that these physical or chemical interactions influence the interfacial shear strength and the macromechanical properties. Differences in the interfacial shear strength correlated with different wetting kinetics due to the different formulations of film former used.

Overview of the atmospheric research program during the International Arctic Ocean Expedition of 1991 (IAOE-91) and its scientific results

Abstract: The broad aim of the Atmospheric program of the International Arctic Ocean Expedition (IAOE-91) was to test the hypothesis that marine biogenically produced dimethyl sulfide (DMS) gas can exert a significant global climatic control. The hypothesis states that DMS is transferred to the atmosphere and is oxidised to form airborne particles. Some of these grow large enough to act as cloud condensation nuclei (CCN) which help determine cloud droplet concentration. The latter has a strong influence on cloud albedo and hence on the radiation balance of the area affected. In summer, the central Arctic is a specially favourable region for studying the natural sulfur cycle in that the open waters surrounding the pack ice are the only significant sources of DMS and there are almost no anthropogenic particle sources. Concentrations of seawater and atmospheric DMS decreased at about the same rate during the period of measurements, (1 August to 6 October, latitudes 75°N to 90°N) spanning about three orders of magnitude. Methane sulfonate and nonsea salt sulfate in the submicrometer particles, which may be derived from atmospheric DMS, also decreased similarly, suggesting that the first part of the hypothesis under test was true. Influences on cloud droplet concentration and radiation balance could not be measured. Size-resolved aerosol chemistry showed a much lower proportion of methane sulfonate to be associated with supermicrometer particles than has been found elsewhere. Its molar ratio to nonsea salt sulfate suggested that the processes controlling the particulate chemistry do not exhibit a net temperature dependence. Elemental analysis of the aerosol also revealed the interesting possibility that debris from Siberian rivers transported on the moving ice represent a fairly widespread source of supermicrometer crustal material within the pack ice. Highly resolved measurements of aerosol number size distributions were made in the diameter range 3 nm to 500 nm. 3 distinct modal sizes were usually present, the “ultrafine”, “Aitken” and “accumulation” modes centred on 14, 45 and 170 nm diameter, respectively. The presence of ultrafine particles, implying recent production, was more frequent than has been found in lower latitude remote marine areas. Evidence suggests that they were mixed to the surface from higher levels. Sudden and often drastic changes in aerosol concentration and size distribution were surprisingly frequent in view of the relatively slowly changing meteorology of the central Arctic during the study period and the absence of strong pollution sources. They were most common in particles likely to have taken part in cloud formation (> 80 nm diameter). 2 factors appear to have been involved in these sudden changes. The 1st was the formation of vertical gradients in aerosol concentration due to interactions between particles and clouds or favoured regions for new particle production during periods of stability. The 2nd was sporadic localised breakdowns of the stability, bringing changed particle concentrations to the measurement level. Probable reasons for these sporadic mixing events were indicated by the structure of the Marine Boundary Layer (MBL) investigated with high resolution rawinsondes. Low level jets were present about 60% of the time, producing conditions conductive to turbulence and shear-induced waves. It is concluded that an even more detailed study of meteorological processes in the MBL in conjunction with more highly time-resolved measurements of gas-aerosol physics and chemistry appears to be essential in any future research aimed at studying the indirect, cloud mediated, effect of aerosol particles. DOI: 10.1034/j.1600-0889.1996.t01-1-00002.x

Interspecific crosses of onion with distant Allium species and characterization of the presumed hybrids by means of flow cytometry, karyotype analysis and genomic in situ hybridization.

Abstract: Interspecific crosses were made by hand-pollination of Allium cepa with pollen of 19 species belonging to nine sections of two subgenera of the genus Allium. In all cases viable plantlets were obtained from ovary culture. The efficiency depended on the relationship of the pollen donor to A. cepa. The hybrid character of the regenerants was checked by morphological comparisons with the parents and/or by one or more cytological methods such as flow cytometric DNA measurement, karyotype analysis, and genomic in situ hybridization (GISH). Hybrids were confirmed for 18 new species combinations. The viable hybrid of the most distant cross resulted from crossing A. cepa with A. sphaerocephalon. The relevance of the verification methods and the potential use of the hybrids for breeding purposes are demonstrated.

Solution Structure of the DNA‐Binding Domain of the Tomato Heat‐Stress Transcription Factor HSF24

Abstract: Two-dimensional-NMR and three-dimensional-NMR experiments were performed to determine the solution structure of the DNA-binding domain of the tomato heat-stress transcription factor HSF24. Samples of uniformly 15N-labeled and 15N, 13C-labeled recombinant proteins were used in the investigation. A near-complete assignment of the backbone 1H, 15N, and 13C resonances was obtained by three-dimensional triple-resonance experiments, whereas three-dimensional 15N-TOCSY-heteronuclear-single-quantum-correlation-spectroscopy, HCCH-COSY and HCCH-TOCSY spectra were recorded for side-chain assignments, 885 non-redundant distance constraints from two-dimensional-homonuclear and three-dimensional-15N-edited and 13C-edited NOESY spectra and 40 hydrogen-bond constraints from exchange experiments were used for structure calculations. The resulting three-dimensional structure contains a three-helix bundle and a small four-stranded antiparallel beta-sheet that forms a hydrophobic core. The two C-terminal helices are parts of a highly conserved helix-turn-helix motif that is probably involved in DNA recognition and binding. In contrast to heat-stress factors from yeast and animals, the plant heat-stress factors lack a loop of 11 amino acid residues inserted between beta3 and beta4. This leads to a tight turn between these beta-strands.

Chromosome 'painting' in plants - a feasible technique?

Abstract: It is shown that chromosome painting is as yet not possible for plants with very complex genomes, neither intra- nor interspecific. The reasons are inefficient blocking of dispersed repetitive sequences and insufficient signal intensity of short unique sequences. Future perspective are indicated.

The use of wheat aneuploids for the chromosomal assignment of microsatellite loci

Abstract: The chromosomal assignment of 64 PCR-amplified microsatellite loci and 29 additional fragments amplified by the same primer pairs is described for bread wheat (Triticum aestivum). The distribution over the different chromosomes and chromosome arms appears to be random. The highest proportion of microsatellite loci is found on the B genome, followed by the A and D genome. About half of the primer pairs amplified unique fragments, while the other half amplified additional fragments. 25% of the primer pairs, mostly designed to clones of a PstI-library, amplify fragments on homoeologous chromosomes. In some cases, more than one fragment on a single chromosome or fragments on non-homoeologous chromosomes occurred. The use of an automated DNA sequencer accounts for the accurate resolution of multiple fragments and enables to differentiate between fragments, amplified by a single primer pair, with size differences as small as two base pairs.

Limited proteolysis of beta-conglycinin and glycinin, the 7S and 11S storage globulins from soybean [Glycine max (L.) Merr.]. Structural and evolutionary implications.

Abstract: The G2 (A2B1a) glycinin subunit from soybean (Glycine max L Merr) was purified and renatured to the homohexameric holoprotein This protein along with purified β-conglycinin were subjected to limited proteolysis by trypsin The generated polypeptide fragments were separated via SDS/PAGE and the amino acid sequence of the N-terminals was determined Four cleavage points were detected in the α-chain A2 of glycinin as well as in the α′-chain of β-conglycinin From the known three-dimensional structure of 7S globulin and the hypothetical model of 7S globulin-like 11S globulin structure, it was possible to draw the conclusion that two distinct types of susceptible sites for proteolytic cleavage are characteristic of the subunits of both globulins The first includes the sequences linking N- and C-terminal domains of both globulins and the sequence of N-terminal extensions of 70-kDa subunits from the vicilin-like 7S globulins The second type includes the loop between β-strands E and F of the N-terminal domain of 11S globulins and of the C-terminal domain of 7S globulins A statistically significant similarity was found between the N-terminal extension of the α′-chain of β-conglycinin and the interdomain linker regions of soybean glycinin and pea legumin It is proposed that the three sequence regions which form the first type of susceptible sites are of similar structural function and might have evolved from the N-terminal segment of a putative single-domain ancestor

Construction of Brassica B genome synteny groups based on chromosomes extracted from three different sources by phenotypic, isozyme and molecular markers

Abstract: The three B genomes of Brassica contained in B. nigra, B. carinata and B. juncea were dissected by addition in B. napus. Using phenotypic, isozyme and molecular markers we characterized 8 alien B-genome chromosomes from B. nigra and B. carinata and 7 from B. juncea by constructing synteney groups. The alien chromosomes of the three different sources showed extensive intragenomic recombinations that were detected by the presence of the same loci in more than one synteny group but flanked by different markers. In addition, intergenomic recombinations were observed. These were evident in euploid AACC plants of the rapeseed phenotype derived from the addition lines carrying a few markers from the B genome due to translocations and recombinations between non-homoeologous chromosomes. The high plasticity of the Brassica genomes may have been an powerful factor in directing their evolution by hybridization and amphiploidy.

Hydrophilization of microporous polypropylene Celgard membranes by the chemical modification technique

Abstract: Microporous hydrophobic polypropylene (PP) membranes (Celgard® 2400 and 2500) were modified by the chemical modification technique to impart permanent hydrophilicity. The modification was carried out in two stages. In the first stage, the membranes were hydroxylated by treatment with aqueous potassium peroxydisulfate solution under a strong flow of nitrogen. In the second stage, the hydroxylated membranes were subjected to grafting of acrylamide using cerric ammonium nitrate as an initiator. Subsequently, acrylamide grafted PP membranes were partially hydrolyzed to have carboxvl functional groups at the membrane surfaces. Under given experimental conditions the grafting also took place within the pores of the microporous structure of hydrophobic PP Celgard® membranes. Modified membranes exhibited permanently wettable characteristics by aqueous solutions and appeared translucent when immersed in water. Contact angle measurements showed excellent wetting properties with water. In contrast to unmodified Celgard® membrane, the modified membranes exhibit water permeability even after repeated drying. Membranes were further characterized by FTIR and ESCA for the different types of functional groups. © 1996 John Wiley & Sons, Inc.

Cloning and expression of an Arxula adeninivorans glucoamylase gene in Saccharomyces cerevisiae

Abstract: The glucoamylase gene of the yeast Arxula adeninivorans Ls3 has been cloned from a genomic library and sequenced The gene could be localized on chromosome 2 from A adeninivorans and comprises 1875 bp The first 16 N-terminal amino acids represent the signal sequence for entering the endomembrane system Comparing the amino acid sequence from this glucoamylase with those of other fungal glucoamylases shows that the glucoamylase of strain Ls3 has a homology to the glucoamylases from Rhizopus oryzae (326%), Saccharomycopsis fibuligera (231%), Aspergillus niger (221%), and Saccharomyces diastaticus (154%) No homology could be detected to the glucoamylase of Schwanniomyces occidentalis By using the GAL1 promoter from Saccharomyces cerevisiae within an autonomously replicating plasmid it was possible to express the isolated Arxula glucoamylase gene in Saccharomyces cerevisiae The transformants secreted 95% of the enzyme into the culture medium The N termini of glucoamylases synthesized in A adeninivorans and S cerevisiae transformants are identical, which means that the signal sequences were cleaved at the same positions during maturation of the proteins The highest glucoamylase activities were reached in the culture medium of S cerevisiae transformants after 36 h of fermentation Northern hybridization showed that the glucoamylase transcripts were formed continuously for up to 70 h These results reveal that the glucoamylase is expressed and secreted more rapidly in the S cerevisiae transformants than in A adeninivorans Ls3

Chloroplast DNA restriction analysis and the infrageneric grouping of Allium (Alliaceae).

Abstract: The utility of chloroplast DNA variation for checking a recently proposed infrageneric classification of the genusAllium was tested. cpDNA restriction patterns of 49 species representing the main subgenera, sections, and subsections of the existing classification were compared. 363 different fragments generated by 4 restriction enzymes were identified and analysed by UPGMA clustering. The resulting phenogram largely confirms the subgeneric classification based on an integration of morphological and other methods.

A set of genetic markers for the chromosomes of the imperfect yeast Arxula adeninivorans

Abstract: The nuclear genome of the anamorphic yeast Arxula adeninivorans was analysed by benomyl-induced haploidization of parasexual hybrids marked with 32 auxotrophic mutations and pulsed field gel electrophoresis followed by DNA hybridization. Twenty-seven genes have been arranged into four linkage groups by haploidization, 15 genes belong to group 1, six to group 2, and three each to groups 3 and 4. Five genes could be localized by DNA hybridization on three out of four separated chromosomes. The gene LYS2 of the largest linkage group 1 and the 25S rDNA were identified on the largest chromosome, the GAA and the TEF1 gene on chromosome 2, and the ILV1 gene of linkage group 4 on the smallest chromosome.