Sabine von Fischer

Brassinosteroid-Regulated Gene Expression

Major brassinosteroid (BR) effects such as BR-induced growth are mediated through genomic pathways because RNA synthesis inhibitors and protein synthesis inhibitors interfere with these processes. A limited number of BR-regulated genes have been identified hitherto. The majority of genes (such as BRU1, CycD3,Lin6, OPR3, and TRIP-1) were identified by comparisons of BR-treated versus control-treated plants. However, altered transcript levels after BR application may not reflect normal physiological events. A complementary approach is the comparison of BR-deficient plants versus wild-type plants. No artificial treatments interfere with endogenous signaling pathways, but a subset of phenotypic alterations of phytohormone-deficient plants most probably is secondary. To identify genes that are subject to direct BR regulation, we analyzed CPD antisense anddwf1-6 (cbb1) mutant plants. Both show a mild phenotype in comparison with BR-deficient mutants such ascpd/cbb3, det2, anddwf4. Plants were grown under two different environments to filter out BR deficiency effects that occur only at certain environmental conditions. Finally, we established expression patterns after BR treatment of wild-type and dwf1-6(cbb1) plants. Ideally, a BR-regulated gene displays a dose-response relationship in such a way that a gene with decreased transcript levels in BR-deficient plants is BR inducible and vice versa. Expression profile analysis of above ground part of plants was performed by means of Affymetrix Arabidopsis Genome Arrays.

A complete BAC-based physical map of the Arabidopsis thaliana genome.

Arabidopsis thaliana is a small flowering plant that serves as the major model system in plant molecular genetics. The efforts of many scientists have produced genetic maps that provide extensive coverage of the genome (http://genome-www.stanford.edu/Arabidopsis/maps.html). Recently, detailed YAC, BAC, P1 and cosmid-based physical maps (that is, representations of genomic regions as sets of overlapping clones of corresponding libraries) have been established that extend over wide genomic areas ranging from several hundreds of kilobases to entire chromosomes. These maps provide an entry to gain deeper insight into the A. thaliana genome structure. A. thaliana has been chosen as the subject of the first large-scale project intended to determine the full genome sequence of a plant. This sequencing project, together with the increasing interest in map-based gene cloning, has highlighted the requirement for a complete and accurate physical map of this plant species. To supply the scientific community with a high-quality resource, we present here a complete physical map of A. thaliana using essentially the IGF BAC library. The map consists of 27 contigs that cover the entire genome, except for the presumptive centromeric regions, nucleolar organization regions (NOR) and telomeric areas. This is the first reported map of a complex organism based entirely on BAC clones and it represents the most homogeneous and complete physical map established to date for any plant genome. Furthermore, the analysis performed here serves as a model for an efficient physical mapping procedure using BAC clones that can be applied to other complex genomes.

CONSTRUCTION AND CHARACTERIZATION OF THE IGF ARABIDOPSIS BAC LIBRARY

Abstract A bacterial artificial chromosome (BAC) library has been established for Arabidopsis thaliana (ecotype Col-0) covering about seven haploid nuclear genome equivalents. This library, called the Institut für Genbiologische Forschung (IGF) BAC library, consists of 10 752 recombinant clones carrying inserts (generated by partial EcoRI digestion) of an average size of about 100 kb in a modified BAC vector, pBeloBAC-Kan. Hybridization with organellar DNA and nuclear repetitive DNA elements revealed the presence of 1.1% clones with mitochondrial DNA, 0.2% clones with plastid DNA, 3.2% clones with the 180 bp paracentromeric repeat, 1.6% clones with 5S rDNA, and 10.8% clones with the 18S-25S rDNA repeat. With its extensive genome coverage, its rather uniformly sized inserts (80 kb <85% <120 kb) and low contamination with organellar DNA, this library provides an excellent resource for A. thaliana genomic mapping, map-based gene cloning, and genome sequencing.

Stabilization of actin filaments by ATP and inorganic phosphate.

Both inorganic orthophosphate and ATP stabilize actin filaments. This is reflected by a reduced nucleotide exchange and by a protection against filament breakdown by SDS or KI. When the filament-stabilizing effect of ATP was maximal, only about 15% of the actin subunits of the filament had bound one molecule of the nucleotide offered in the stabilizing solution.

Closure of a Rapidly Exchanging Calcium Compartment in Rat Cardiac Myocytes by Lanthanum

Abstract Enzymatically isolated myocytes from adult rats were used to measure 45Ca-uptake from salt media of reduced Ca2+-content (0.1 mM) with normal (4 mM) or elevated (20 mM) potassium concentrations. Ca2+-uptake was interrupted by filtration followed by rapid chasing the filter with salt solutions containing no Ca2+, 2 mM Ca2+ or 2 mM La3+. Rate and extent of 45Ca-uptake of resting cells were found to be 3-fold enhanced when chasing was performed with La3+-containing media. In contrast La3+ does not affect Ca2+-exchange of depolarized cells, the fluxes of which approximate rates sufficiently high for contraction activation and that are sensitive to Ca2+-channel blockers. The effect of La3+ on resting cells suggests the existence of a small rapidly exchanging La3+-sensitive Ca2+-compartment located adjacent to the plasma membrane. This compartment is though to be either closed or has become La3+-insensitive in activated cells. The subsarcolemmal cysternae of the SR, the so-called “peripheral couplings” are most likely the morphological substrate of this compartment.

Debating volume : architectural versus electrical amplification in the League of Nations, 1926–28

In the debates following the 1926–27 competition for the new headquarters of the League of Nations in Geneva, conflicting contemporary ideas about architecture were manifested in approaches to sound. The competition coincided with the formation of architectural acoustics as a profession and academic discipline. Hannes Meyer and Hans Wittwer, together with their acoustic adviser, for example, employed electrical technologies such as loudspeakers as integral parts in what they called scientific architecture. Other projects, prominently that of Le Corbusier and Pierre Jeanneret, denied the feasibility of electro-acoustic amplification, arguing that the intelligibility of speech had to be granted by the geometric form of the Assembly Hall’s architecture. Throughout the process, the competition brief’s outline of having nearly 3,000 seats was criticised for being acoustically unfeasible. Considering the state of contemporary loud-speaker technology, this scale of an auditorium seemed incompatible with the aim of literal, acoustic understanding of speeches in the League of Nations’ Assembly Hall. As in a Tower of Babel, diplomatic understanding was thus not only a political but also a technical problem. Later on, this genuine problem provoked Richard Neutra’s statement that such meetings were altogether unnecessary. The debates foregrounded the expertise of acousticians such as Franz Max Osswald, the founder of Switzerland’s first laboratory of applied acoustics at ETH, and Gustave Lyon in Paris, who stood for architectural amplification by sound reflections. There was no consensus on employing architectural or electrical techniques to ensure intelligibility of speech, and the acoustic debate was couched in rhetoric which either downplayed or exaggerated the coming of age of electro-acoustic amplification. Studying the ideological and technological trajectories of the 1920s, different approaches to architectural acoustics shed new light on the reasoning of modernism’s champion Sigfried Giedion, and others. The heated debates following the competition gave remarkable prominence to arguments about acoustics.In the debates following the 1926–27 competition for the new headquarters of the League of Nations in Geneva, conflicting contemporary ideas about architecture were manifested in approaches to soun...

Listening and the League of Nations: Acoustics Are the Argument

Abstract : In the debates following the 1926–27 competition for the new headquarters of the League of Nations in Geneva, the acoustic aspect was largely overlooked. The competition coincided with the formation of architectural acoustics as a profession and an academic discipline. Looking at this coincidence sheds new light on the reasoning of Peter Meyer and Sigfried Giedion, who, in support of Le Corbusier and Pierre Jeanneret’s scheme, gave remarkable prominence to arguments about acoustics. The transmission of speech in the large Assembly Hall with seating for 2,700 could not be resolved by traditional techniques, and opinions on the modern method of electroacoustic amplification differed greatly. The protagonists who stepped forward in favor of Le Corbusier and Pierre Jeanneret’s scheme, for which Gustave Lyon served as acoustic advisor, emphasized the sound quality of their design for the large Assembly Hall. Despite the acoustically infeasible competition brief, they declared literal understanding, based on the intelligibility of speech, to be a fundamental function of the League of Nations headquarters. The questions raised in this paper relate to architecture’s aurality and visuality, as well as claims concerning function in debates on Modernism. Diplomatic understanding was evidently at stake in the League of Nations’ political program, but, curiously, literal understanding was neglected in the acoustic design for the Assembly Hall by many of the competitors and the jury, and—apart from a short remark by Jacques Gubler in 1985 —was subsequently overlooked by historians. Keywords: acoustics; function; functionality; League of Nations; Gustave Lyon; Franz Max Osswald. DOI: http://dx.doi.org/10.4995/LC2015.2015.495

Review: The House of Light and Entropy by Alessandra Ponte

Alessandra Ponte The House of Light and Entropy Architecture Words series, London: AA Publications, 2014, 228 pp., 33 b/w illus. £15.00, ISBN 9781907896170 In an era when global scale and New World histories steer the agendas of historical discourse, Alessandra Ponte’s insistence on looking at the specificity of places, sites, and landscapes has gained exceptional momentum. The six essays in The House of Light and Entropy span the spectrum of Ponte’s far-reaching research interests, woven into a tight fabric of critical reflections. They trace histories of the cultivation of nature, of mapping, and of media in the context of American sites that have one characteristic in common: the lawn, the sand desert, and the ice desert are vast. As landscapes conceived of as “empty,” they have repeatedly been claimed as sites of scientific and artistic testing. Recognizing the futility of hegemonic claims on these overpowering landscapes, Ponte’s narration acknowledges the volatility of any historiography of such sites, illuminating them via contrasting multiple arguments as she draws them into and out of perspective. In terms of the choreography of the six essays, the reader is left without doubt that Ponte’s interests lie far from the picturesque and from visual studies. On the contrary, what is at stake are social, cultural, and economic questions relating to the occupation of land by humans, by machines, and by media. The first subject of Ponte’s investigation is the ubiquitous suburban lawn. This essay was originally published in the catalog for the 1998 exhibition The American Lawn: The Surface of Everyday Life at the Canadian Centre for Architecture in Montreal, which Ponte cocurated with a team of seven architects.1 She points out that at the beginning of the twentieth century the concept of the “landscape garden” was replaced by that of a “natural landscape,” thereby alerting us to the idea that naturalism is a construction and preparing us to follow her further arguments. The two quotes that open …