Circadian clock-regulated expression of phytochrome and cryptochrome genes in Arabidopsis.

Many physiological and biochemical processes in plants exhibit endogenous rhythms with a period of about 24 h. Endogenous oscillators called circadian clocks regulate these rhythms. The circadian clocks are synchronized to the periodic environmental changes (e.g. day/night cycles) by specific stimuli; among these, the most important is the light. Photoreceptors, phytochromes, and cryptochromes are involved in setting the clock by transducing the light signal to the central oscillator. In this work, we analyzed the spatial, temporal, and long-term light-regulated expression patterns of the Arabidopsis phytochrome (PHYA to PHYE) and cryptochrome (CRY1 and CRY2) promoters fused to the luciferase (LUC(+)) reporter gene. The results revealed new details of the tissue-specific expression and light regulation of the PHYC and CRY1 and 2 promoters. More importantly, the data obtained demonstrate that the activities of the promoter::LUC(+) constructs, with the exception of PHYC::LUC(+), display circadian oscillations under constant conditions. In addition, it is shown by measuring the mRNA abundance of PHY and CRY genes under constant light conditions that the circadian control is also maintained at the level of mRNA accumulation. These observations indicate that the plant circadian clock controls the expression of these photoreceptors, revealing the formation of a new regulatory loop that could modulate gating and resetting of the circadian clock.

Molecular analysis of variability within the toxigenic Aspergillus ochraceus species.

Genetic variability of Aspergillus ochraceus was examined at the DNA level. Based on the HaeIII-Bg/II generated mitochondrial DNA restriction profiles, most isolates could be classified into two distinct groups. These two groups could also be distinguished by the random amplified polymorphic DNA technique, and with telomeric PCR amplifications. Phylogenetic analysis of sequences of the intergenic transcribed spacer region of some of the strains resulted in a dendrogram with the same topology as that based on mitochondrial DNA and amplified DNA data. None of the isolates with type 2 mtDNA profiles produce ochratoxins. Some strains (e.g., A. ochraceus ICMP 939) displayed strain-specific mitochondrial DNA patterns, and their amplified DNA profiles were also different from all other A. ochraceus strains examined.

Analysis of genetic variability within the genus Petromyces.

Phenotypic and genotypic features of three teleomorphic species, Petromyces alliaceus, P. albertensis and P. muricartus and some related anamorphic Aspergillus species were compared. The dendrogram based on carbon source utilisation data revealed a close relationship between P. muricarus and the A. ochraceus strains examined. P. alliaceus and P. albertensis strains were very closely related to each other. A dendrogram with similar topology was obtained by analysing sequences of the intergenic transcribed spacer regions of representatives of these species. P. alliaceus and P. albertensis strains could only be distinguished by the random amplified polymorphic DNA technique. These strains possibly represent a single species closely related to Aspergillus section Flavi, while the anamorph of P. turicatus is a member of Aspergillus section Circumdati. Our results indicate that Aspergillus section Circumdati is in need of taxonomic revision.

Double-stranded RNA mycoviruses in species of Aspergillus sections Circumdati and Fumigati.

Isolates (178) belonging to Aspergillus sections Fumigati, Candidi, Clavati, and Circumdati were tested for the presence of double-stranded RNA (dsRNA) genomes. Altogether, 5.6% of the Aspergillus strains examined were infected with dsRNAs. dsRNA segments indicative of mycovirus infection were observed for the first time in Neosartorya hiratsukae, Neosartorya quadricincta, Petromyces alliaceus, and Aspergillus clavatus strains. Correlation was not observed between ochratoxin production and dsRNA content of the strains. This is the first report on the detection of naturally occurring dsRNAs in Aspergillus species that are able to reproduce sexually. The detection of dsRNA in sexual aspergilli gave us a chance to examine the transmission of these segments through ascospores. A Neosartorya hiratsukae strain transmitted the dsRNAs efficiently through sexual spores, while the stromata embedding the asci in Petromyces alliaceus did not transmit one of the dsRNA segments. The 0.6-kb dsRNA segment that was present in the single-stromatal cultures was found to be located in the mitochondrial fraction of this strain. This observation indicates that some mechanisms exist in aspergilli to exclude cytoplasmically located dsRNA molecules from stromatal structures.

Ochratoxin production by Aspergillus species.

Ochratoxin production was tested in 172 strains representing species in sections Fumigati, Circumdati, Candidi, and Wentii of the genus Aspergillus by an immunochemical method using a monoclonal antibody preparation against ochratoxin A. Ochratoxin A was detected in Aspergillus ochraceus, A. alliaceus, A. sclerotiorum, A. sulphureus, A. albertensis, A. auricomus, and A. wentii strains. This is the first report of production of ochratoxins in the latter three species. Ochratoxin production by these species was confirmed by high-performance thin-layer chromatography and by high-performance liquid chromatography. The chemical methods also indicated the production of ochratoxin B by all of the Aspergillus strains mentioned above.

[Gas chromatographic methods for flavor testing in cooked pork (M. semimembranosus)]. / Gaschromatographische Untersuchungsmethoden zur Aromaprüfung in gekochtem Schweinefleisch (M. semimembranosus)

The authors elaborated a gas chromatographic method for the separation and partial identification of ether-soluble volatile flavour constituents obtained from the semimembranous muscles of raw and cooked (100 degree C) pork by distillation and subsequent extraction and condensation. The different constituents were identified using KOVATS index values. The KOVATS indices of the flavour constituents were calculated from the mean values of triplicate measurements performed at different temperatures, and compared with the values for test substances. The isothermal chromatograms of the samples tested at various temperatures were combined in such a manner that they contained of each isothermal record only the parts with the best separation and without superpositions and non-appearences of peaks. By means of the KOVATS index, 32 volatile constituents could be identified with great probability in the ether extract of the meat flavour. The presence of 8 of these constituents was also confirmed by thin-layer chromatography.