Andrea Palágyi

Functional Analysis of Amino-Terminal Domains of the Photoreceptor Phytochrome B

At the core of the circadian network in Arabidopsis (Arabidopsis thaliana), clock genes/proteins form multiple transcriptional/translational negative feedback loops and generate a basic approximately 24-h oscillation, which provides daily regulation for a wide range of processes. This temporal organization enhances the fitness of plants only if it corresponds to the natural day/night cycles. Light, absorbed by photoreceptors, is the most effective signal in synchronizing the oscillator to environmental cycles. Phytochrome B (PHYB) is the major red/far-red light-absorbing phytochrome receptor in light-grown plants. Besides modulating the pace and phase of the circadian clock, PHYB controls photomorphogenesis and delays flowering. It has been demonstrated that the nuclear-localized amino-terminal domain of PHYB is capable of controlling photomorphogenesis and, partly, flowering. Here, we show (1) that PHYB derivatives containing 651 or 450 amino acid residues of the amino-terminal domains are functional in mediating red light signaling to the clock, (2) that circadian entrainment is a nuclear function of PHYB, and (3) that a 410-amino acid amino-terminal fragment does not possess any functions of PHYB due to impaired chromophore binding. However, we provide evidence that the carboxyl-terminal domain is required to mediate entrainment in white light, suggesting a role for this domain in integrating red and blue light signaling to the clock. Moreover, careful analysis of the circadian phenotype of phyB-9 indicates that PHYB provides light signaling for different regulatory loops of the circadian oscillator in a different manner, which results in an apparent decoupling of the loops in the absence of PHYB under specific light conditions.

Analysis of genetic variability within the genus Petromyces.

Phenotypic and genotypic features of three teleomorphic species, Petromyces alliaceus, P. albertensis and P. muricatus and some related anamorphic Aspergillus species were compared. The dendrogram based on carbon source utilisation data revealed a close relationship between P. muricatus 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. muricatus is a member of Aspergillus section Circumdati. Our results indicate that Aspergillus section Circumdati is in need of taxonomic revision.

Isolation and Characterization of Antagonistic Bacillus Strains Capable to Degrade Ethylenethiourea

In this study, more than 150 bacteria showing antagonistic properties against bacterial and fungal pathogens of the tomato plant were isolated and characterized. The most efficient agents against these phytopathogenic microorganisms belong to the genus Bacillus: the best biocontrol isolates were representatives of Bacillus subtilis, B. mojavensis and B. amyloliquefaciens species. They intensively produced fengycin or/and surfactin depsipeptide antibiotics and also proved to be excellent protease secretors. It was proved, that the selected strains were able to use ethylenethiourea (ETU) as sole nitrogen source. These antagonistic and ETU-degrading Bacillus strains can be applied as biocontrol and also as bioremediation agents.

Identification of Aspergillus species in Central Europe able to produce G-type aflatoxins

The occurrence of potential aflatoxin producing fungi was examined in various agricultural products and indoor air in Central European countries including Hungary, Serbia and Croatia. For species identification, both morphological and sequence based methods were applied. Aspergillus flavus was detected in several samples including maize, cheese, nuts, spices and indoor air, and several isolates were able to produce aflatoxins. Besides, three other species of Aspergillus section Flavi, A. nomius, A. pseudonomius and A. parasiticus were also isolated from cheese, maize and indoor air, respectively. This is the first report on the occurrence of A. nomius and A. pseudonomius in Central Europe. All A. nomius, A. pseudonomius and A. parasiticus isolates were able to produce aflatoxins B1, B2, G1 and G2. The A. nomius isolate came from cheese produced very high amounts of aflatoxins (above 1 mg ml⁻¹). All A. nomius, A. pseudonomius and A. parasiticus isolates produced much higher amounts of aflatoxin G1 then aflatoxin B1. Further studies are in progress to examine the occurrence of producers of these highly carcinogenic mycotoxins in agricultural products and indoor air in Central Europe.

A New Concept to Secure Food Safety Standards against Fusarium Species and Aspergillus Flavus and Their Toxins in Maize

Commercial maize hybrids are exposed to different degrees of ear infection by toxigenic fungal species and toxin contamination. Their resistance to different fungi and toxin relationships are largely unknown. Without this knowledge, screening and breeding are not possible for these pathogens. Seven- to tenfold differences were found in resistance to Fusarium spp., and there was a five-fold difference in ear coverage (%) in response to A. flavus. Three hybrids of the twenty entries had lower infection severity compared with the general means for toxigenic species. Three were highly susceptible to each, and 14 hybrids reacted differently to the different fungi. Differences were also observed in the toxin content. Again, three hybrids had lower toxin content in response to all toxigenic species, one had higher values for all, and 16 had variable resistance levels. Correlations between infection severity and deoxynivalenol (DON) content were 0.95 and 0.82 (p = 0.001) for F. graminearum and F. culmorum, respectively. For fumonisin and F. verticillioides ear rot, the Pearson correlation coefficient (r) was 0.45 (p = 0.05). Two independent isolates with different aggressiveness were used, and their mean X values better described the resistance levels. This increased the reliability of the data. With the introduction of this methodological concept (testing the resistance levels separately for different fungi and with two isolates independently), highly significant resistance differences were found. The resistance to different fungal species correlated only in certain cases; thus, each should be tested separately. This is very useful in registration tests and post-registration screening and breeding. This would allow a rapid increase in food and feed safety.

Different species of legumes grown in combination with oats as green forage

Green fodder mixture trials were carried out with GK Impala, a winter hardy, fall sown oat variety registered in 2005 intercropped either with winter vetch or winter pea in a crop year when the spring was dry (2003) and in another one (2004) when the precipitation was optimal in spring. The two components of mixtures were sown 50% each. A four-replicate randomised complete block design was used with 50 m2 plots. The results were compared to the mixtures of spring oats and vetch; and spring oats and pea, respectively. The green matter of fall sown crops was cut by scythe late May, whereas that of spring crops early June.Data demonstrate that the green forage yield and protein production of fall sown oats as a monocrop and intercropped with vetch was higher than those of spring types. Green matter and dry matter yield varied with season, and were more advantageous in the year 2004, when there was more precipitation. The crude protein content of winter vetch and the crude protein production of the mixture fa...