University of Marburg

About: University of Marburg is a education organization based out in Marburg, Germany. It is known for research contribution in the topics: Population & Gene. The organization has 23195 authors who have published 42907 publications receiving 1506069 citations. The organization is also known as: Philipps University of Marburg & Philipps-Universität.

Indole alkaloid biosynthesis in Catharanthus roseus: new enzyme activities and identification of cytochrome P450 CYP72A1 as secologanin synthase.

Abstract: Summary The molecular characterization of CYP72A1 from Catharanthus roseus (Madagascar periwinkle) was described nearly a decade ago, but the enzyme function remained unknown. We now show by in situ hybridization and immunohistochemistry that the expression in immature leaves is epidermis-specific. It thus follows the pattern previously established for early enzymes in the pathway to indole alkaloids, suggesting that CYP72A1 may be involved in their biosynthesis. The early reactions in that pathway, i.e. from geraniol to strictosidine, contain several candidates for P450 activities. We investigated in this work two reactions, the conversion of 7-deoxyloganin to loganin (deoxyloganin 7-hydroxylase, DL7H) and the oxidative ring cleavage converting loganin into secologanin (secologanin synthase, SLS). The action of DL7H has not been demonstrated in vitro previously, and SLS has only recently been identified as P450 activity in one other plant. We show for the first time that both enzyme activities are present in microsomes from C. roseus cell cultures. We then tested whether CYP72A1 expressed in E. coli as a translational fusion with the C. roseus P450 reductase (P450Red) has one or both of these activities. The results show that CYP72A1 converts loganin into secologanin.

Narcolepsy - clinical spectrum, aetiopathophysiology, diagnosis and treatment.

Abstract: Narcolepsy is a rare brain disorder that reflects a selective loss or dysfunction of orexin (also known as hypocretin) neurons of the lateral hypothalamus. Narcolepsy type 1 (NT1) is characterized by excessive daytime sleepiness and cataplexy, accompanied by sleep-wake symptoms, such as hallucinations, sleep paralysis and disturbed sleep. Diagnosis is based on these clinical features and supported by biomarkers: evidence of rapid eye movement sleep periods soon after sleep onset; cerebrospinal fluid orexin deficiency; and positivity for HLA-DQB1*06:02. Symptomatic treatment with stimulant and anticataplectic drugs is usually efficacious. This Review focuses on our current understanding of how genetic, environmental and immune-related factors contribute to a prominent (but not isolated) orexin signalling deficiency in patients with NT1. Data supporting the view of NT1 as a hypothalamic disorder affecting not only sleep-wake but also motor, psychiatric, emotional, cognitive, metabolic and autonomic functions are presented, along with uncertainties concerning the 'narcoleptic borderland', including narcolepsy type 2 (NT2). The limitations of current diagnostic criteria for narcolepsy are discussed, and a possible new classification system incorporating the borderland conditions is presented. Finally, advances and obstacles in the symptomatic and causal treatment of narcolepsy are reviewed.

Identification of genes in the bW/bE regulatory cascade in Ustilago maydis

Abstract: In the phytopathogenic fungus Ustilago maydis, the switch to filamentous growth and pathogenic development is controlled by a heterodimeric transcription factor consisting of the bW and bE homeodomain proteins. To identify genes in the regulatory cascade triggered by the bW/bE heterodimer, we have constructed strains in which transcription of the b genes is inducible by either arabinose or nitrate. At different time-points after induction, genes that are switched on or off were identified through a modified, non-radioactive RNA fingerprint procedure. From 348 gene fragments isolated initially, 48 fragments representing 34 different genes were characterized in more detail. After eliminating known genes, false positives and genes influenced in their expression profile by media conditions, 10 new b-regulated genes were identified. Of these, five are upregulated and five are downregulated in presence of the b heterodimer. Two do not share significant similarity to database entries, whereas the other eight show similarity to disulphide isomerases, exochitinases, cation antiporters, plasma membrane (H+)-ATPases, acyl transferases, a capsular associated protein of Cryptococcus neoformans, DNA polymerases X, as well as to a potential protein of Neurospora crassa. We demonstrate that in one of the early upregulated genes, the promoter can be bound by a bW/bE fusion protein in vitro. Interestingly, three out of the four genes that are downregulated by the b heterodimer appear upregulated after pheromone stimulation, suggesting a connection to the mating process.

Prandtl and Rayleigh number dependence of the Reynolds number in turbulent thermal convection

Abstract: The Prandtl and Rayleigh number dependences of the Reynolds number in turbulent thermal convection following from the unifying theory by Grossmann and Lohse [J. Fluid Mech. 407, 27 (2000); Phys. Rev. Lett. 86, 3316 (2001)] are presented and compared with various recent experimental findings. This dependence Re(Ra,Pr) is more complicated than a simple global power law. For Pr=5.5 and 108