Variation in mate-recognition pheromones of the fungal genus Microbotryum

Mate recognition is an essential life-cycle stage that exhibits strong conservation in function, whereas diversification of mating signals can contribute directly to the integrity of species boundaries through assortative mating. Fungi are simple models, where compatibility is based on the recognition of pheromone peptides by corresponding receptor proteins, but clear patterns of diversification have not emerged from the species examined, which are few compared with mate signaling studies in plant and animal systems. In this study, candidate loci from Microbotryum species were used to characterize putative pheromones that were synthesized and found to be functional across multiple species in triggering a mating response in vitro. There is no significant correlation between the strength of a species'' response and its genetic distance from the pheromone sequence source genome. Instead, evidence suggests that species may be strong or weak responders, influenced by environmental conditions or developmental differences. Gene sequence comparisons reveals very strong purifying selection on the a₁ pheromone peptide and corresponding receptor, but significantly less purifying selection on the a₂ pheromone peptide that corresponds with more variation across species in the receptor. This represents an exceptional case of a reciprocally interacting mate-recognition system in which the two mating types are under different levels of purifying selection.     

Developing an indicator-modelling approach to forecast changes in nitrogen critical load exceedance across Europe arising from agricultural reform

Atmospheric nitrogen (N) deposition above the critical load causes eutrophication with adverse impacts on biodiversity. Average Accumulated critical load Exceedance (AAE) is a measure of the amount of critical load exceedance and the area of habitat which is affected, and has been adopted in Europe as a pressure indicator for biodiversity. In Europe, AAE is calculated by the Coordination Centre for Effects (CCE) of the United Nations Economic Commission for Europe based on modelled nitrogen deposition and country-level reporting of critical load thresholds and ecosystem area. Due to differences in country-level reporting, AAE values for semi-natural habitats may show large differences across Europe. This paper therefore describes the development of a simpler approach to the modelling of habitat eutrophication. The eutrophication indicator model is applicable to all habitats for which empirical critical loads for nutrient nitrogen have been defined and is easily configured to assess impacts of modelled policies or scenarios on AAE. Outputs from the model showed a high correlation with published AAE data (R² = 0.80) and replicated broad spatial patterns in AAE, but under-estimated actual values by a factor of 2.5. This variation was traced primarily to the use of habitat-specific nitrogen deposition by the CCE which calculates higher nitrogen deposition to forest areas, but also to differences between countries in the critical load thresholds used and the areas of sensitive ecosystems reported. Sensitivity testing showed that exceedance calculations were particularly sensitive to the critical load threshold used, since nitrogen deposition across Europe lies in the middle of most critical load ranges. The indicator model was used to forecast AAE under two scenarios: socio-economic changes under a business as usual scenario to 2025, and the additional effect of agricultural reform where both direct support to farmers and market support were removed. Ammonia emissions showed a net decrease by 2025, with strong regional differentiation. Emissions increased in former Soviet bloc countries and decreased mainly in south west Europe and Finland. Agricultural reform had little additional impact on ammonia emissions. AAE was forecast to decrease by 49% by 2025, due mainly to reductions in emissions of oxidised N from industry and transport, independent of agricultural reform. However, as oxidised N decreases, the relative contribution of N from agricultural sources will increase, and policy measures which reduce ammonia emissions will have increasing relevance for reducing AAE.     

Possible Case of Maternal Transmission of Feline Spongiform Encephalopathy in a Captive Cheetah

Feline spongiform encephalopathy (FSE) is considered to be related to bovine spongiform encephalopathy (BSE) and has been reported in domestic cats as well as in captive wild cats including cheetahs, first in the United Kingdom (UK) and then in other European countries. In France, several cases were described in cheetahs either imported from UK or born in France. Here we report details of two other FSE cases in captive cheetah including a 2^nd case of FSE in a cheetah born in France, most likely due to maternal transmission. Complete prion protein immunohistochemical study on both brains and peripheral organs showed the close likeness between the two cases. In addition, transmission studies to the TgOvPrP4 mouse line were also performed, for comparison with the transmission of cattle BSE. The TgOvPrP4 mouse brains infected with cattle BSE and cheetah FSE revealed similar vacuolar lesion profiles, PrP^d brain mapping with occurrence of typical florid plaques. Collectively, these data indicate that they harbor the same strain of agent as the cattle BSE agent. This new observation may have some impact on our knowledge of vertical transmission of BSE agent-linked TSEs such as in housecat FSE, or vCJD.     

Radioisotopic assay of picomolar amounts of coenzyme A

A two-step method of determining reduced coenzyme A (CoASH) concentrations in tissue or cell extracts is described. In the first step, CoASH is reacted with acetylphosphate in a reaction catalyzed by phosphotransacetylase to yield acetyl-CoA. Acetyl-CoA is then condensed with [14C]oxaloacetate by citrate synthase to give [14C]citrate. This method allows the measurement of 10-200 pmol of CoASH. By omitting the phosphotransacetylase step, measurement of the same amount of acetyl-CoA is possible.     

Mass fragmentographic determination of xanthine and hypoxanthine in biological fluids

The method presented for the simultaneous determination of xanthine and hypoxanthine, uses mass-fragmentography in the electron impact (EI) mode, after the gas chromatographic separation of butylated derivatives. Butylation, rather than methylation, is used in order to avoid interference coming from exogenous caffeine, which is frequently encountered. [7,9-¹⁵N]Xanthine is used as the internal standard, and for each sample, a blank is obtained by xanthine oxidase reaction. In the biological fluids studied the sensitivity was about 50 ng/ml.