Zur Beurteilung der Feldresistenz von Wintergerste (Hordeum vulgare L.) gegenüber Zwergrost (Puccinia hordei Otth)

Eine anorganische Phosphatase aus Escherichia coli wurde als neuer Enzym‐Marker zum ELISA‐Test bei vier Nepoviren‐raspberry ringspot virus, strawberry latent ringspot virus, tomato black ring virus und arabis mosaic virus‐benutzt. Ein Vergleich des ELISA bei Nutzung von Peroxydase aus Meerrettich und von anorganischer Pyrophosphatase als Marker ergab, daß die Nutzung von Pyrophosphatase einen empfindlicheren Nachweis der Viren in gereinigten Präparaten, in Extrakten aus krautigen Testpflanzen sowie in Rohsäften von Himbeerpflanzen erlaubte.     

Substrate scope of a dehydrogenase from Sphingomonas species A1 and its potential application in the synthesis of rare sugars and sugar derivatives

Rare sugars and sugar derivatives that can be obtained from abundant sugars are of great interest to biochemical and pharmaceutical research. Here, we describe the substrate scope of a short‐chain dehydrogenase/reductase from Sphingomonas species A1 (SpsADH) in the oxidation of aldonates and polyols. The resulting products are rare uronic acids and rare sugars respectively. We provide insight into the substrate recognition of SpsADH using kinetic analyses, which show that the configuration of the hydroxyl groups adjacent to the oxidized carbon is crucial for substrate recognition. Furthermore, the specificity is demonstrated by the oxidation of d ‐sorbitol leading to l ‐gulose as sole product instead of a mixture of d ‐glucose and l ‐gulose. Finally, we applied the enzyme to the synthesis of l ‐gulose from d ‐sorbitol in an in vitro system using a NADH oxidase for cofactor recycling. This study shows the usefulness of exploring the substrate scope of enzymes to find new enzymatic reaction pathways from renewable resources to value‐added compounds.     

Heterothallism revealed in the root rot fungi Berkeleyomyces basicola and B. rouxiae

Berkeleyomyces basicola and Berkeleyomyces rouxiae, two sister species previously treated collectively as Thielaviopsis basicola, reside in the Ceratocystidaceae (Microascales, Ascomycota). Both species are important root pathogens of many important agricultural crops and ornamental plants. Although T. basicola has been known for more than 150y, a sexual state has never been found and it has been assumed to be an asexual pathogen. The aim of this study was to determine the mating strategy of the two Berkeleyomyces species. Investigation of the genome sequences of two B. basicola isolates allowed for the complete characterization of the MATlocus, revealing that it has a typical heterothallic mating system with the MAT1-1andMAT1-2 idiomorphs occurring in different isolates. PCR amplification using mating type primers developed in this study, showed that the MAT1-1-1andMAT1-2-1 genes were also present in different isolates of B. rouxiae. Pairing of isolates representing the two mating types of both species,using a variety of techniques failed to produce sexual structures. Although we have found no direct evidence that they reproduce sexually, these fungi are clearly heterothallic with both mating types occurring in some countries suggesting that a cryptic sexual cycle could exist for them.     

Nitrogen fixation and diversity of benthic cyanobacterial mats on coral reefs in Curaçao

Coral Reefs - Benthic cyanobacterial mats (BCMs) have increased in abundance on coral reefs worldwide. However, their species diversity and role in nitrogen fixation are poorly understood. We...     

Characterization of Erwinia amylovora strains using random amplified polymorphic DNA fragments (RAPDs)

The genetic diversity among 16 strains of Erwinia amylovora, chosen to represent different host plant origins and geographical regions, was investigated by RAPD analysis. One strain of Erwinia herbicola and one of Agrobacterium vitis were used as outgroups. Ninety-eight different RAPD fragments were produced by polymerase chain reaction amplification with six different 10-mer primers. RAPD banding profiles were found that enabled the Erw. amylovora strains to be distinguished from one another. Cluster analysis based on the number of RAPD fragments shared between strains showed that strains of Erw. amylovora isolated from subfamily Pomoideae formed a single group, whereas two strains from Rubus (subfamily Rosoideae) formed a second group. Two strains isolated from Asian pear on Hokkaido, Japan, formed a third group. Sets of RAPD fragments were identified that enabled each of the two host-range groups and one geographical region (Hokkaido) of Erw. amylovora strains to be unambiguously distinguished from one another and from the outgroups. This study shows that strains of Erw. amylovora exhibit genetic diversity detectable by RAPD analysis, and that molecular and statistical analysis of RAPD fragments can be used both to distinguish between strains and to determine relatedness between them.     

Osmium-labeled polynucleotides. Incorporation of additional heavy atoms (mercury) via ligand substitution reactions

The reaction of osmium tetroxide with biological materials, particularly nucleic acids, has considerable utility in electron microscopy and X-ray crystallography. This heavymetal label introduces an electrophilic center which may serve as a means of attachment of nucleophiles. Nucleophilic ligand substitution reactions have been exploited as a means of adding more heavy metals (mercury) onto the osmium label. Furthermore, the technique is quite general and could be used to modify the osmium label with, for example, fluorescent groups. The nucleophilic exchange reactions have also been studied using ¹H nmr spectroscopy with a representative heterocyclic osmate ester derivative, the bis(pyridine) osmate ester derivative of TMP. These studies have defined the nature of the ligands which lead to stable osmium labels.     

The U3 Promoter and the nef Gene of Simian Immunodeficiency Virus (SIV) smmPBj1.9 Do Not Confer Acute Pathogenicity upon SIVagm

Two chimeric proviruses comprising the U3 promoter and the nef gene of simian immunodeficiency virus (SIV) smmPBj1.9 in addition to other genomic regions of SIVagm3mc from African green monkeys (Cercopithecus aethiops) were constructed. The derived chimeric viruses (SIVagm3mc/SIVsmmPBj1.9) were both able to replicate in nonstimulated peripheral blood leukocytes from pig-tailed macaques (Macaca nemestrina), a biological property often correlated with acute pathogenicity. However, only one of the chimeric viruses was acutely pathogenic, inducing a rapid depletion of the peripheral CD4⁺ T cells in two infected pig-tailed macaques within 10 days after infection in a manner similar to infection with SIVsmmPBj1.9 itself. The other chimeric virus actively replicated during the first 8 weeks after experimental infection of two pig-tailed macaques but induced neither acute disease nor CD4⁺ T-cell depletion for 113 weeks after infection. Thus, the U3 promoter and the nef gene of SIVsmmPBj1.9 alone appear to be insufficient to confer acute pathogenicity to SIVagm3mc.     

On the responses of laughing gull chicks (Larus atricilla) to the calls of adults II. Age changes and responses to different types of call

Three age-groups of laughing gull chicks were tested with playback of recordings of calls of their parents and calls of neighbouring adults. The chicks in each group showed response to the playback calls, and recognition of the voices of their parents. The chicks in the early group (1 to 3 days post-hatching) showed the least evidence of parent recognition: the chicks of the late group (12 to 28 days post-hatching) showed the lowest levels of response in general.Evidence of relationships between variation in the behaviour in the tests and variation in the test recordings was found from correlation analysis, the type of call initiating positive response, and analysis of temporal association. This evidence, and the results of tests which allowed responses to the parents' crooning and responses to the parents' ke-hah calls to be compared for chicks in the late group, indicate that whereas the filial approach behaviour of very young chicks is stimulated by crooning but suppressed by ke-hah and long-calls, this behaviour in older chicks requires the occurrence of ke-hah calls or long-calls for its elicitation. However the ke-hah calls and long-calls of adults other than the parents continue to have negative effects on the behaviour of older chicks.It is argued that this progression in discrimination of the voices of the parents and the changes in responsiveness to the different types of adult calls are consistent with functional requirements, both from the point of view of changes in a growing chick's social situation and from the point of view of the characteristics of the calls. The changes are also discussed from a developmental point of view.