Effect of shear rate and culture pH on the production of xylanase by Thermomyces lanuginosus

Summary The pH-value and the stirrer speed during cultivation of the thermophilic fungus Thermomyces lanuginosus were found to have a pronounced influence on xylanase production using corn cobs as carbon source. The highest xylanase activity of 32500 nkat/ml was produced in labscale fermentation within 118 hours at a stirrer speed of 50 rpm and a controlled pH-value of 7.5.     

Definition and characterization of an artificial En/Spm-based transposon tagging system in transgenic tobacco

A transposon tagging system for heterologous hosts, based on the maize En/Spm transposable element, was developed in transgenic tobacco. In this system, the two En-encoded trans-acting factors necessary for excision are expressed by fusing their cDNAs to the CaMV 35S promoter. The dSpm receptor component is inserted in the 5-untranslated leader of the bar gene. Germinal revertants can therefore be selected by seed germination on L-PPT-containing medium or by spraying seedlings with the herbicide Basta. Using this bar-based excision reporter construct, an average frequency of germinal excision of 10.1% was estimated for dSpm-S, an En/Spm native internal deletion derivative. Insertion of En-foreign sequences in a receptor, such as a DHFR selectable marker gene in dSpm-DHFR, does not abolish its capacity to transpose. However, dSpm-DHFR has a lower frequency of somatic and germinal excision than dSpm-S. Revertants carrying a transposed dSpm-DHFR element can be selected with methotrexate. Germinal excision is frequently associated with reinsertion but, as in maize, dSpm has a tendency to integrate at chromosomal locations linked to the donor site. Concerning the timing of excision, independent germinal transpositions are often found within a single seed capsule. All activity parameters analysed suggest that transposon tagging with this system in heterologous hosts should be feasible.     

Genetics of sex determination in flowering plants

Most flowering plant species are hermaphroditic, but a small number of species in most plant families are unisexual (i.e., an individ-ual will produce only male or female gametes). Because species with unisexual flowers have evolved repeatedly from hermaphroditic progenitors, the mechanisms controlling sex determination in flowering plants are extremely diverse. Sex is most strongly determined by genotype in all species but the mechanisms range from a single controlling locus to sex chromosomes bearing several linked locirequired for sex determination. Plant hormones also influence sex expression with variable effects from species to species. Here, we review the genetic control of sex determination from a number of plant species to illustrate the variety of extant mechanisms. We emphasize species that are now used as models to investigate the molecular biology of sex determination. We also present our own investigations of the structure of plant sex chromosomes of white campion (Silene latifolia - Melan-drium album). The cytogenetic basis of sex determination in white campion is similar to mammals in that it has a male-specific Y-chromosome that carries dominant male determining genes. If one copy of this chromosome is in the genome, the plant is male. Otherwise it is female. Like mammalian Y-chromosomes, the white campion Y-chromosome is rich in repetitive DNA. We isolated repetitive sequences from microdissected Y-chromosomes of white campion to study the distribution of homologous repeated sequences on the Y-chromosome and the other chromosomes. We found the Y to be especially rich in repetitive sequences that were generally dispersed over all the white campion chromosomes. Despite its repetitive character, the Y-chromosome is mainly euchromatic. This may be due to the relatively recent evolution of the white campion sex chromosomes compared to the sex chromosomes of animals. © 1994 Wiley-Liss, Inc.     

Expression of CD44 Splice Variants During Lymphocyte Activation and Tumor Progression

Recently, splice variants of CD44 have been described that confer metastatic potential to non-metastasizing rat pancreatic carcinoma and sarcoma cell lines. Using antibodies against variant CD44 (CD44v) sequences, we have examined the expression of variant CD44 glycoproteins on human lymphoid cells and tissues and in colorectal neoplasia. Lymphohematopoietic cells express low levels of CD44v glycoproteins. During the process of lymphocyte activation in vitro and in vivo, expression of CD44v glycoproteins is transiently upregulated. The reaction pattern of various antibodies indicates that these CD44 variants contain the domain encoded by exon v6, which is part of the variant that confers metastatic capability. In human colorectal neoplasia we observed overexpression of CD44 splice variants in all invasive carcinomas. Already at early stages of colorectal tumor progression exon v5 epitopes were overexpressed. Tumor progression was strongly related to expression of CD44 isoforms containing exon v6 encoded domains. The findings establish CD44 variants as tumor progression markers in colorectal cancer.     

Anostraca,Notostraca, Laevicaudata and Spinicaudata of Pannonian region and in its Austrian area

The northwestern area of the Pannonian Lowland extends into Austria. The climatic and hydrologic attributes of this biographic region promote the existence of extremely astatic bodies water lacking any fish and hence the occurrence of Anostraca, Notostraca, Laevicaudata and Spinicaudata. Zoogeographical and ecological features as well as the extinction of species due to anthropogenic influence are described.Dedicated to Prof. Dr F. Berger, Lunz, Austria, on the occasion of his 90th birthdayDedicated to Prof. Dr F. Berger, Lunz, Austria, on the occasion of his 90th birthday     

The S. pombe cdc16 gene is required both for maintenance of p34cdc2 kinase activity and regulation of septum formation: a link between mitosis and cytokinesis?

In the fission yeast Schizosaccharomyces pombe, septum formation and cytokinesis are dependent upon the initiation, though not the completion of mitosis. A number of cell cycle mutants which show phenotypes consistent with a defect in the regulation of septum formation have been isolated. A mutation in the S. pombe cdc16 gene leads to the formation of multiple septa without cytokinesis, suggesting that the normal mechanisms that limit the cell to the formation of a single septum in each cycle do not operate. Mutations in the S. pombe early septation mutants cdc7, cdc11, cdc14 and cdc15 lead to the formation of elongated, multinucleate cells, as a result of S phase and mitosis continuing in the absence of cytokinesis. This suggests that in these cells, the normal mechanisms which initiate cytokinesis are defective and that they are unable to respond to this by preventing further nuclear cycles. Genetic analysis has implied that the products of some of these genes may interact with that of the cdc16 gene. To understand how the processes of septation and cytokinesis are regulated and coordinated with mitosis we are studying the early septation mutants and cdc16. In this paper, we present the cloning and analysis of the cdc16 gene. Deletion of the gene shows that it is essential for cell proliferation: spores lacking a functional cdc16 gene germinate, complete mitosis and form multiple septa without undergoing cell cleavage.(ABSTRACT TRUNCATED AT 250 WORDS)     

Apios americana,a fly-pollinated papilionaceous flower?

In the flowers ofApios americana the vexillum remains ± in its bud position. In this way, a dark cavity is formed displaying a bright window at its base. Insect visitors are attracted to the hidden inflorescences by scent. In their attempt to reach the window they trigger an explosive release of stigma and pollen. Stigmatic fluid glues pollen to the visitor. All characters of the flower fit well into the myiophilous syndrome and thus flies are expected to be the proper pollinators.Apios americana seems to be the only myiophilous exception within the predominantly melittophilousFabaceae.     

Distribution,causal agents,and infection dynamic of emerging ink disease of sweet chestnut in Southern Switzerland

Emerging diseases caused by both native and exotic pathogens represent a main threat to forest ecosystems worldwide. The two invasive soilborne pathogens Phytophthora cinnamomi and Phytophthora × cambivora are the causal agents of ink disease, which has been threatening Castanea sativa in Europe for several centuries and seems to be re-emerging in recent years. Here, we investigated the distribution, causal agents, and infection dynamics of ink disease in southern Switzerland. A total of 25 outbreaks were identified, 19 with only P. cinnamomi, 5 with only P. × cambivora, and 1 with both species. Dendrochronological analyses showed that the disease emerged in the last 20–30 years. Infected trees either died rapidly within 5–15 years post-infection or showed a prolonged state of general decline until death. Based on a generalized linear model, the local risk of occurrence of ink disease was increased by an S-SE aspect of the chestnut stand, the presence of a pure chestnut stand, management activities, the proximity of roads and buildings, and increasing annual mean temperature and precipitation. The genetic structure of the local P. cinnamomi population suggests independent introductions and local spread of the pathogen.