Transient reduction in secreted 32 kD chitinase prevents somatic embryogenesis in the carrot (Daucus carota L.) variant ts11

At the nonpermissive temperature, somatic embryos of the temperature-sensitive (ts) carrot (Daucus carota L.) cell variant ts11 only proceed beyond the globular embryo stage in the presence of medium conditioned by wild-type cells. The causative component in the conditioned medium has been identified as an acidic 32 kD endochitinase. An antiserum raised against the 32 kD chitinase detected this protein in culture medium from ts11 embryo cultures grown at the permissive temperature as well as at the nonpermissive temperature. No difference in biochemical characteristics or in effect on ts11 embryo development could be detected between the 32 kD chitinase purified from wild-type cultures and the chitinase from ts11 cultures grown at the permissive or at the nonpermissive temperature. Compared to the amount present in a ts11 embryo culture at the permissive temperature, a reduction in the amount of 32 kD chitinase was observed during the temperature-sensitive period at the nonpermissive temperature. These results imply that the arrested embryo phenotype of ts11 is not the result of a structural difference in its 32 kD chitinase, but is the result of a transient decrease in the amount of 32 kD chitinase present. Morphological observations indicate that the ts11 phenotype is pleiotropic and also affects the cell wall of nonembryogenic cells. © 1995 Wiley-Liss, Inc.     

Production of halogenated compounds byBjerkandera adusta

The white-rot fungusBjerkandera adusta produces volatile chlorinated phenyl compounds. The main compounds identified were 3-chloro-4-methoxybenzaldehyde (3-chloro-p-anisaldehyde), 3-chloro-4-methoxybenzyl alcohol (3-chloro-p-anisyl alcohol), 3,5-dichloro-4-methoxybenzaldehyde (3,5-dichloro-p-anisaldehyde), and 3,5-dichloro, 4-methoxybenzyl alcohol (3,5-dichloro-p-anisyl alcohol).p-Anisaldehyde, veratraldehyde and the corresponding alcohols,p-anisyl alcohol and veratryl alcohol were produced simultaneously. Even with a very low concentration of chloride in the medium (< 10^–5 m), chlorinated aromatic compounds were still observed. Addition of bromide to the culture medium led to the production of brominated compounds: 3-bromo-4-methoxybenzaldehyde, 3-bromo-4-methoxybenzyl alcohol, 3,5-dibromo-4-methoxybenzaldehyde and 3-bromo-5-chloro-4-methoxybenzaldehyde. These brominated compounds have not previously been reported as natural products. Although iodo-aromatic compounds were not produced by supplementation of the medium with iodide, isovanillin was found in the culture broth under these conditions. This compound may be formed by substitution of the iodine intermediate by a hydroxyl group on the third carbon of the ring. Diiodomethane or chloroiodomethane were also found. It is the first time that the production of halomethane has been related to the production of halogenated aromatic compounds. All the strains tested have these capabilities.     

Homologous recombination of monkey alpha-satellite repeats in an in vitro simian virus 40 replication system: possible association of recombination with DNA replication.

To study homologous recombination between repeated sequences in an in vitro simian virus 40 (SV40) replication system, we constructed a series of substrate DNAs that contain two identical fragments of monkey alpha-satellite repeats. Together with the SV40-pBR322 composite vector encoding Apr and Kmr, the DNAs also contain the Escherichia coli galactokinase gene (galK) positioned between two alpha-satellite fragments. The alpha-satellite sequence used consists of multiple units of tandem 172-bp sequences which differ by microheterogeneity. The substrate DNAs were incubated in an in vitro SV40 DNA replication system and used to transform the E. coli galK strain DH10B after digestion with DpnI. The number of E. coli galK Apr Kmr colonies which contain recombinant DNAs were determined, and their structures were analyzed. Products of equal and unequal crossovers between identical 172-bp sequences and between similar but not identical (homeologous) 172-bp sequences, respectively, were detected, although those of the equal crossover were predominant among all of the galK mutant recombinants. Similar products were also observed in the in vivo experiments with COS1 cells. The in vitro experiments showed that these recombinations were dependent on the presence of both the SV40 origin of DNA replication and SV40 large T antigen. Most of the recombinant DNAs were generated from newly synthesized DpnI-resistant DNAs. These results suggest that the homologous recombination observed in this SV40 system is associated with DNA replication and is suppressed by mismatches in heteroduplexes formed between similar but not identical sequences.     

Consequences of a tidal reduction for the salt-marsh vegetation in the Oosterschelde estuary (The Netherlands)

A storm-surge barrier was constructed in the mouth of the Oosterschelde, a euhaline mesotidal estuary in the SW Netherlands (mean tidal range 3.6 m). As a consequence, the tidal range and the Mean High Water in the estuary have been reduced to about 88% of their original values.During the final construction stage of this barrier (1986–87) both were reduced to a maximum of 65% for more than 18 months. During this period, large-scale die-back of the vegetation occurred in vast areas on the salt marshes; locally, a complete die-back of the vegetation took place. Glycophytes and disturbance indicating species appeared on a large scale and grew abundantly. After the new tidal regime had been established, the vegetation recovered. The species characteristic of disturbance, are gradually being replaced by perennial salt marsh species. In addition, most species are shifting into zones of lower elevation, which correspond (in 1990/1991) more or less with the original flooding frequencies. Moreover, in many basins the levee-species Halimione portulacoides and Elymus pycnanthus are far more prominent than before, probably as a result of the strong ripening of the soil that has occurred in these basins during the extra tidal reduction. In 1991, four years after the establishment of the new tidal regime, the salt marsh vegetation had still not been stabilized.     

Cytological characterization of isolated sperm cells of perennial ryegrass (Lolium perenne L.)

Summary The cytoplasmic content and the distribution of intramembrane particles (IMPs) of the plasma membrane of isolated sperm cells of perennial ryegrass (Lolium perenne L.) have been characterized using flow cytometry, transmission electron microscopy, confocal scanning laser microscopy and freeze-fracture studies. The isolated haploid sperm cells contain a variety of cell organelles with the exception of microtubules. Proplastids and plastids with starch were observed, although only rarely. Vacuoles containing remnants of organelles and stacked lamellae of endoplasmic reticulum with cytoplasmic inclusions were observed frequently, indicating that autophagy takes place. The number of mitochondria varies from 11 to 26 with an average of 17. Generally, the nucleus has a lobed shape and displays various interphasic stages of chromatin condensation. The analysis of the number of mitochondria and the nuclear state did not show evidence of sperm cell dimorphism. The cytological variability observed, could be explained by differences in developmental stages already present in vivo at the moment of isolation. No correlation between the number of mitochondria and the nuclear cross-sectioned area and/or the condensation state of the chromatin could be found. The density of intramembrane particles of the plasma membrane on the exoplasmic fracture face is more than twice that on the protoplasmic fracture face. That is the opposite of what was found for sporophytic cells of perennial ryegrass. These results are discussed in relation to the potential use of these cells for biotechnology and developmental studies.     

Production of panose from maltose by intact cells of Aureobasidium pullulans

Panose, a major component of isomalto-oligosaccharides, was selectively produced from maltose using transglucosylation reaction catalyzed by intact cells of Aureobasidium pullulans. When 50 %(w/v) maltose was used as a substrate, the maximum concentration of panose accumulated in the final reaction mixture was about 50 %(w/w) after 120 hr reaction at 55 °C.     

Expression and secretion of human lipocortin-1 by promoter and signal sequence of STA1 from Saccharomyces diastaticus

Summary For the secretion of human lipocortin-1 (LC-1) in yeast, a expression and secretion vector was constructed by using the promoter and signal sequence of glucoamylase gene (STA1) of Saccharomyces diastaticus. After the cDNA of human LC-1 was ligated with the secretion vector, the resulting hybrid plasmid was transformed into S. diastaticus. When the recombinant S. diastaticus was cultivated in YPD medium, LC-1 was expressed and secreted into the extracellular medium, yielding LC-1 protein at a concentration of 2.5 g/mL.     

Dopaminergic and adrenergic receptors synergistically stimulate browning in 3T3-L1 white adipocytes

Journal of Physiology and Biochemistry - The browning of white adipose tissue (WAT) has attracted considerable attention in the scientific community as a popular strategy for enhancing energy...