Molecular recognition in plant immunity

Plant pathogens constitute a major threat to global food security. The use of naturally resistant crop varieties can limit crop losses, however new races of pathogen can arise that are able to overcome these defences. Plant breeding for race-specific resistance typically relies on disease-resistance genes, which generally encode proteins with nucleotide-binding and leucine-rich repeat domains (NB-LRRs). NB-LRRs are a large of proteins found in both plants and animals, with plant NB-LRRs further classified by the presence of N-terminal coiled-coil or toll-interleukin receptor domains. Although qualitative models exist to describe R-protein regulation and activation, these are predominantly based on genetic and molecular studies. Biochemical investigations into R-protein function have been hampered by difficulties obtaining sufficient yields of material. When suitable material has been identified, biochemical studies have been used to complement well-established in planta assays to validate numerous hypotheses. This work describes the screening processes undertaken to obtain R-protein domains suitable for downstream experiments. Using E. coli for high-throughput screening of constructs from a single R-protein, traditional construct design to investigate multiple R-protein domains and expanding our expression hosts to eukaryotic systems we successfully purified four coiled-coil domains and a single NBARC domain for use in downstream experiments. Characterisation of this NBARC domain by circular dichroism and small-angle X-ray scattering indicates that the protein is well-folded and stable in solution, allowing in vitro investigations. In testing models for R-protein regulation we were able to confirm previous findings, such as low levels of ATPase activity, however we were unable to find evidence for a commonly cited method of signal repression. A preliminary crystal structure of the NBARC domain shows significant similarity to Apaf-1, and highlights the importance of conserved motifs in NBARC architecture. The tools presented here should prove a valuable resource to complement existing models to better understand the structure, biochemistry, and ultimately regulation of plant R-proteins

Sculpting with fire: celebrating ephemerality at AfrikaBurn 2015 in the Tankwa Karoo, South Africa

Land art, and some installation art, is usually aimed at relatively temporarily manipulating the surface of the earth. AfrikaBurn takes place annually in the near-desert of the Tankwa Karoo, South Africa. It is a communal event unique to Africa, and manifests as a fleeting week-long series of interventions in the natural environment, partially aimed at creating and then actively destroying free-standing public sculptures, some of which are huge and intricate. AfrikaBurn gives any one of the thousands of participants an opportunity to be inspired on any scale to generate artworks that take into account a principle that no debris whatsoever is left behind on the surface of the earth after a week-long celebration of creative energies. Unlike, for instance, an artwork built on the edge of the Indian Ocean in the Eastern Cape, where rough tidal seas would ensure gradual destruction, at AfrikaBurn, the sacrificial method of choice is controlled rapid burning, under the direction of a specified firemaster. This paper seeks to unbundle some aspects of land and installation art in Southern Africa with specific reference to AfrikaBurn 2015 events and anti-fracking initiatives. This is within a context that takes into account recognition that even seemingly durable public sculptures are subject to change and may even physically disappear with the passing of time

Shortest Paths Through Pseudo-Random Points in the dd-Cube

A lower bound for the length of the shortest path through n points in [0, Ild is given in terms of the discrepancy function of the n points. This bound is applied to obtain an analogue for several pseudorandom sequences to the known limit behavior of the length of the shortest path through n independent uniformly distributed random observations from [0, l]d

Darrell Huff and Fifty Years of How to Lie with Statistics

Over the last fifty years, How to Lie with Statistics has sold more copies than any other statistical text. This note explores the factors that contributed to its success and provides biographical sketches of its creators: author Darrell Huff and illustrator Irving Geis

Vocational guidance problems in a secondary shcool.

Typewritten sheets in cover. Thesis (M.A.)--Boston University This item was digitized by the Internet Archive