Biomedical subjects

Wolfgang Frank

Publications and source records attributed to Wolfgang Frank.

5 recordsLinked to original sources

PubMed2006

Biosynthesis of C9-aldehydes in the moss Physcomitrella patens.

After wounding, the moss Physcomitrella patens emits fatty acid derived volatiles like octenal, octenols and (2E)-nonenal. Flowering plants produce nonenal from C18-fatty acids via lipoxygenase and hydroperoxide lyase reactions, but the moss exploits the C20 precursor arachidonic acid for the formation of these oxylipins. We describe the isolation of the first cDNA (PpHPL) encoding a hydroperoxide lyase from a lower eukaryotic organism. The physiological pathway allocation and characterization of a downstream enal-isomerase gives a new picture for the formation of fatty acid derived volatiles from lower plants. Expression of a fusion protein with a yellow fluorescent protein in moss protoplasts showed that PpHPL was found in clusters in membranes of plastids. PpHPL can be classified as an unspecific hydroperoxide lyase having a substrate preference for 9-hydroperoxides of C18-fatty acids but also the predominant substrate 12-hydroperoxy arachidonic acid is accepted. Feeding experiments using arachidonic acid show an increase in the 12-hydroperoxide being metabolized to C8-aldehydes/alcohols and (3Z)-nonenal, which is rapidly isomerized to (2E)-nonenal. PpHPL knock out lines failed to emit (2E)-nonenal while formation of C8-volatiles was not affected indicating that in contrast to flowering plants, PpHPL is only involved in formation of a specific subset of volatiles.

Aldehyde-Lyases↗

PubMed2006

Novel micro-RNAs and intermediates of micro-RNA biogenesis from moss.

Micro-RNAs (miRNAs) are one class of small non-coding RNAs that have important regulatory roles in higher plants. Much less is known about their prevalence and function in lower land plants. Previously we cloned 100 non-structural small RNAs from the moss Physcomitrella patens but could annotate only 11 as miRNAs. To identify additional moss miRNAs among cloned small RNAs we have analyzed their genomic sequences for a characteristic miRNA precursor-like structure. This analysis revealed 19 new moss miRNAs that are predicted to be encoded by 22 putative foldbacks. Northern blot analysis confirmed the expression of 14 new miRNA representatives. Half of these were gametophore specific, the rest were detected at low levels in the protonema. We predicted 12 genes as targets of nine new miRNAs. Three of these show homology to transcription factors and the others appear to play roles in diverse physiological processes including light and cytokine signaling, which have not to date been shown to be regulated by a miRNA in flowering plants. Four target genes, which show homology to ATN1-like protein kinase, NAC transcription factors and a cytokinin receptor, have been validated by miRNA-mediated mRNA cleavage. In addition, our analysis revealed that seven small RNAs represent miRNA* and three represent intermediates of pre-miRNA processing, providing evidence for specific DICER-like cleavage steps during miRNA biogenesis in moss. Our findings suggest that miRNAs are common in mosses and set the stage for the elucidation of their varied biological functions.

Base Sequence↗

PubMed2005

Moss (Physcomitrella patens) functional genomics--Gene discovery and tool development, with implications for crop plants and human health.

Recently, the moss Physcomitrella patens was established as a versatile tool in plant functional genomics. Mosses represent the oldest living clade of land plants, separated by approximately 450 million years of evolution from crop plants. Consequently, mosses contain metabolites and genes not known from these seed plants. In Physcomitrella, nuclear genes can be targeted by homologous recombination as efficiently as in yeast, allowing reverse genetics approaches in plants at high-throughput levels for the first time. Comprehensive expressed sequence tag databases gave new insights into the levels of diversity in land plants which are now ready to be exploited in plant biotechnology. In forward genetics screens, saturated tagged mutant collections help to unravel novel gene - function relationships. Additionally, proteomics tools are at hand to analyse subcellular proteomes, as well as the phosphoproteome, as the core of eukaryotic signal transduction. Moreover, specifically designed Physcomitrella strains can produce human therapeutic proteins safely and cost-effectively in bioreactors.

Bioreactors↗

PubMed2004

Physcomitrella patens is highly tolerant against drought, salt and osmotic stress.

In order to determine the degree of tolerance of the moss Physcomitrella patens to different abiotic stress conditions, we examined its tolerance against salt, osmotic and dehydration stress. Compared to other plants like Arabidopsis thaliana, P. patens exhibits a high degree of abiotic stress tolerance, making it a valuable source for the identification of genes effecting the stress adaptation. Plants that had been treated with NaCl tolerated concentrations up to 350 mM. Treatments with sorbitol revealed that plants are able to survive concentrations up to 500 mM. Furthermore, plants that had lost 92% water on a fresh-weight basis were able to recover successfully. For molecular analyses, a P. patens expressed sequence tag (EST) database was searched for cDNA sequences showing homology to stress-associated genes of seed plants and bacteria. 45 novel P. patens genes were identified and subjected to cDNA macroarray analyses to define their expression pattern in response to water deficit. Among the selected cDNAs, we were able to identify a set of genes that is specifically up-regulated upon dehydration. These genes encode proteins exerting their function in maintaining the integrity of the plant cell as well as proteins that are known to be members of signaling networks. The identified genes will serve as molecular markers and potential targets for future functional analyses.

Bryopsida↗

PubMed2004

Talc pleurodesis: basic fibroblast growth factor mediates pleural fibrosis.

STUDY OBJECTIVES: Patients with recurrent pleural effusions secondary to malignancy are subjected to pleurodesis if clinically indicated. Pleurodesis involves the introduction of a sclerosing agent into the pleural space. Talc is one of the most commonly used sclerosing agents in treating patients with recurrent, symptomatic malignant pleural effusions. However, the mechanisms whereby talc mediates pleural fibrosis remain unclear. We hypothesized that the intrapleural instillation of talc induces the pleural mesothelial production of basic fibroblast growth factor (bFGF), which is responsible for pleural fibrosis. METHODS: Samples of pleural fluid collected from 23 patients with malignant pleural effusions and 6 patients with congestive heart failure (control group) were included in this study. A tumor grading scale (1 to 9) was used to demonstrate the extent of the tumor. In vitro pleural mesothelial cells (PMCs) were activated with talc, and the conditioned medium was collected to evaluate bFGF levels by enzyme-linked immunosorbent assay. The bFGF-induced proliferation of fibroblasts was studied by [(3)H]thymidine incorporation. The messenger RNA expression of bFGF in talc-activated PMCs was determined by Northern analysis. RESULTS: In this study, we demonstrated that patients who have undergone successful pleurodesis following intrapleural talc insufflation have significantly higher levels of bFGF in their pleural fluid compared to those who do not respond to pleurodesis. In addition, we found a significant negative correlation between bFGF levels and tumor size. Talc-activated PMCs produce significantly higher levels of bFGF compared to control, which correlates with bFGF messenger RNA expression in PMCs stimulated with talc. The neutralization of pleural fluids and conditioned medium from talc-stimulated PMCs with bFGF antibodies significantly inhibits the bFGF-induced proliferation of pleural fibroblasts. CONCLUSIONS: An important outcome of this study was the finding that patients with extensive tumor involvement of the pleural mesothelium have a significantly lower pleural fluid bFGF response to talc compared to those who have limited involvement. Patients with limited pleural disease and higher bFGF responses go on to have successful pleurodesis, demonstrating that the presence of a mesothelium that is free of tumor enhances the possibility of success. In vitro PMCs stimulated with talc release biologically active bFGF.

Adult↗