A second gene at the tomato Cf-4 locus confers resistance to cladosporium fulvum through recognition of a novel avirulence determinant

The tomato Cf-4 and Cf-9 genes confer resistance to the leaf mould pathogen Cladosporium fulvum and map at a complex locus on the short arm of chromosome 1. It was previously shown that the gene encoding Cf-4, which recognizes the Avr4 avirulence determinant, is one of five tandemly duplicated homologous genes (Hcr9-4s) at this locus. Cf-4 was identified by molecular analysis of rare Cf-4/Cf-9 disease-sensitive recombinants and by complementation analysis. The analysis did not exclude the possibility that an additional gene(s) located distal to Cf-4 may also confer resistance to C. fulvum. We demonstrate that a number of Dissociation-tagged Cf-4 mutants, identified on the basis of their insensitivity to Avr4, are still resistant to infection by C. fulvum race 5. Molecular analysis of 16 Cf-4 mutants, most of which have small chromosomal deletions in this region, suggested the additional resistance specificity is encoded by Hcr9-4E. Hcr9-4E recognizes a novel C. fulvum avirulence determinant that we have designated Avr4E.     

The cover of living and dead corals from airborne remote sensing

Trends in coral cover are widely used to indicate the health of coral reefs but are costly to obtain from field survey over large areas. In situ studies of reflected spectra at the coral surface show that living and recently dead colonies can be distinguished. Here, we investigate whether such spectral differences can be detected using an airborne remote sensing instrument. The Compact Airborne Spectrographic Imager (Itres Research Ltd, Canada) was flown in two configurations: 10 spectral bands with 1-m² pixels and 6 spectral bands with 0.25-m² pixels. First, we show that an instrument with 10 spectral bands possesses adequate spectral resolution to distinguish living Porites, living Pocillopora spp., partially dead Porites, recently dead Porites (total colony mortality within 6 months), old dead (>6 months) Porites, Halimeda spp., and coralline red algae when there is no water column to confuse spectra. All substrata were distinguished using fourth-order spectral derivatives around 538 nm and 562 nm. Then, at a shallow site (Tivaru) at Rangiroa Atoll, Tuamotu Archipelago (French Polynesia), we show that live and dead coral can be distinguished from the air to a depth of at least 4 m using first- and fourth-order spectral derivatives between 562–580 nm. However, partially dead and recently dead Porites colonies could not be distinguished from an airborne platform. Spectral differences among substrata are then exploited to predict the cover of reef substrata in ten 25-m² plots at nearby Motu Nuhi (max depth 8 m). The actual cover in these plots was determined in situ using quadrats with a 0.01-m² grid. Considerable disparity occurred between field and image-based measures of substrate cover within individual 25-m² quadrats. At this small scale, disparity, measured as the absolute difference in cover between field and remote-sensing methods, reached 25% in some substrata but was always less than 10% for living coral (99% of which consisted of Porites spp.). At the scale of the reef (all ten 25-m² quadrats), however, disparities in percent cover between imagery and field data were less than 10% for all substrata and extremely low for some classes (e.g. <3% for living Porites, recently dead Porites and Halimeda). The least accurately estimated substrata were sand and coralline red algae, which were overestimated by absolute values 7.9% and 6.6%, respectively. The precision of sampling was similar for field and remote-sensing methods: field methods required 19 plots to detect a 10% difference in coral cover among three reefs with a statistical power of 95%. Remote-sensing methods required 21 plots. However, it took 1 h to acquire imagery over 92,500 m² of reef, which represents 3,700 plots of 25 m² each, compared with 3 days to survey 10 such plots underwater. There were no significant differences in accuracy between 1-m² and 0.25-m² image resolutions, suggesting that the advantage of using smaller pixels is offset by reduced spectral information and an increase in noise (noise was observed to be 1.6–1.8 times greater in 0.25-m² pixels). We show that airborne remote sensing can be used to monitor coral and algal cover over large areas, providing that water is shallow and clear, and that brown fleshy macroalgae are scarce, that depth is known independently (e.g. from sonar survey).     

Atropisomeric quinazolin-4-one derivatives are potent noncompetitive alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonists

Piriqualone (1) was found to be an antagonist of AMPA receptors. Structure activity optimization was conducted on each of the three rings in 1 to afford a series of potent and selective antagonists. The sterically crowded environment surrounding the N-3 aryl group provided sufficient thermal stability for atropisomers to be isolated. Separation of these atropisomers resulted in the identification of (+)-38 (CP-465,022), a compound that binds to the AMPA receptor with high affinity (IC50 = 36 nM) and displays potent anticonvulsant activity.     

Hexagonal shaped ice spicules in frozen antifreeze protein solutions

In the presence of antifreeze proteins from both Antarctic and Arctic fishes, water freezes in the form of long c-axis spikes or spicular-like crystals. Transmission electron microscopy of the Pt/C replicas of the freeze fractured spicular ice in a small capillary revealed the presence of many hexagonally shaped structures whose cross-sectional dimensions were between 0.5 and 10 microm. Well-defined parallel faces were associated with most fractured and etched spicules. When fracture planes occurred near the tip of a spicule, well-defined pyramidal faces were apparent. Steps were sometimes associated with these pyramidal spicular crystal faces. On some of the replicas obvious roughening of certain crystal faces of the spicule was observed, suggesting that the antifreeze proteins may have adsorbed to those faces.     

Nuclear import of PKCdelta is required for apoptosis: identification of a novel nuclear import sequence

We have shown previously that protein kinase Cdelta (PKCdelta) is required for mitochondrial-dependent apoptosis. Here we show that PKCdelta is imported into the nucleus of etoposide-treated cells, that nuclear import is required for apoptosis and that it is mediated by a nuclear localization signal (NLS) in the C-terminus of PKCdelta. Mutation of the caspase cleavage site of PKCdelta inhibits nuclear accumulation in apoptotic cells, indicating that caspase cleavage facilitates this process. Expression of the PKCdelta catalytic fragment (CFdelta) in transfected cells results in nuclear localization and apoptosis. We show that the PKCdelta NLS is required for nuclear import of both full-length PKCdelta and CFdelta, and drives nuclear localization of a multimeric green fluorescent protein. Mutations within the NLS of CFdelta prevent nuclear accumulation and block apoptosis. Conversely, nuclear expression of a kinase-negative catalytic fragment (KN-CFdelta) protects cells from etoposide-induced apoptosis. Mutation of the NLS blocks the ability of KN-CFdelta to protect against etoposide-induced apoptosis. These results indicate that PKCdelta regulates an essential nuclear event(s) that is required for initiation of the apoptotic pathway.     

Advances in plant biotechnology and its adoption in developing countries

Developing countries are already benefiting and should continue to benefit significantly from advances in plant biotechnology. Insect-protected cotton containing a natural insecticide protein from Bacillus thuringiensis (Bt cotton) is providing millions of farmers with increased yields, reduced insecticide costs and fewer health risks. Many other useful plant biotechnology products that can benefit poor farmers and consumers are in the research and development pipelines of institutions in developing countries, and should soon reach farmers' fields.     

The impact of restrictive entry criterion during the placebo lead-in period

In the study of depression, most randomized clinical trials have design features that attempt to sample from a stable patient population. One commonly used design feature is to require patients to maintain some minimum baseline symptom severity score during a placebo lead-in period. One intent of this design feature is to evaluate the behavior of patients prior to administration of active medication. If, during the lead-in period, patients do not maintain minimum symptom severity, the patients are excluded from the remainder of the study, the theory being that the excluded patients are not part of a stable patient population and hence are not likely to demonstrate efficacy of a truly effective treatment. This presentation investigates the effectiveness of a restrictive entry criterion and proposes an alternative explanation for what is usually defined as placebo response.