Despite the fact that coffee rust was first investigated scientifically more than a century ago, and that the disease is one of the major constraints to coffee production - constantly changing the socio-economic and historical landscape of the crop - critical aspects of the life cycle of the pathogen, Hemileia vastatrix, remain unclear. The asexual urediniospores are regarded as the only functional propagule: theoretically, making H. vastatrix a clonal species. However, the well-documented emergence of new rust pathotypes and the breakdown in genetic resistance of coffee cultivars, present a paradox.
Methods and Results
Here, using computer-assisted DNA image cytometry, following a modified nuclear stoichiometric staining technique with Feulgen, we show that meiosis occurs within the urediniospores. Stages of spore development were categorised based on morphology, from the spore-mother cell through to the germinating spore, and the relative nuclear DNA content was quantified statistically at each stage.
Conclusions
Hidden sexual reproduction disguised within the asexual spore (cryptosexuality) could explain why new physiological races have arisen so often and so quickly in Hemileia vastatrix. This could have considerable implications for coffee breeding strategies and may be a common event in rust fungi, especially in related genera occupying the same basal phylogenetic lineages. 相似文献
We investigate the dynamics of the 2009 influenza A (H1N1/S-OIV) pandemic by analyzing data obtained from World Health Organization containing the total number of laboratory-confirmed cases of infections--by country--in a period of 69 days, from 26 April to 3 July, 2009. Specifically, we find evidence of exponential growth in the total number of confirmed cases and linear growth in the number of countries with confirmed cases. We also find that, i) at early stages, the cumulative distribution of cases among countries exhibits linear behavior on log-log scale, being well approximated by a power law decay; ii) for larger times, the cumulative distribution presents a systematic curvature on log-log scale, indicating a gradual change to lognormal behavior. Finally, we compare these empirical findings with the predictions of a simple stochastic model. Our results could help to select more realistic models of the dynamics of influenza-type pandemics. 相似文献
Postural instability is one of the most incapacitating symptoms of Parkinson’s disease (PD) and appears to be related to cognitive deficits. This study aims to determine the cognitive factors that can predict deficits in static and dynamic balance in individuals with PD. A sociodemographic questionnaire characterized 52 individuals with PD for this work. The Trail Making Test, Rule Shift Cards Test, and Digit Span Test assessed the executive functions. The static balance was assessed using a plantar pressure platform, and dynamic balance was based on the Timed Up and Go Test. The results were statistically analysed using SPSS Statistics software through linear regression analysis. The results show that a statistically significant model based on cognitive outcomes was able to explain the variance of motor variables. Also, the explanatory value of the model tended to increase with the addition of individual and clinical variables, although the resulting model was not statistically significant The model explained 25–29% of the variability of the Timed Up and Go Test, while for the anteroposterior displacement it was 23–34%, and for the mediolateral displacement it was 24–39%. From the findings, we conclude that the cognitive performance, especially the executive functions, is a predictor of balance deficit in individuals with PD. 相似文献
The present study aimed to investigate the role of four non-native invertebrates in supporting fish biomass as well as their influence on the carbon flow into the Volta Grande reservoir food web. The fish samples were carried out quarterly between October 2015 and July 2016 using gillnets. At the sampled sites, four non-native invertebrates (golden mussel, Asian clam, trumpet snail and Amazonian prawn), which are potential prey for fish in the Volta Grande reservoir, were collected by targeted sampling using a Petersen-type bottom dredger and semi-circular sieves. The gut contents of the fish were collected and analyzed under stereoscope, and samples of muscle tissue of these fish, as well as the four non-native invertebrate species sampled, were submitted for isotopic analysis. Results obtained by the present study, by both gut content and stable isotopic analyses, pointed to a trophic structure where non-native species represent not only a strong component of the fish community, but also their main carbon source. Based on gut contents and isotopic mixing models, we found that together, non-native prey are essential carbon sources for the fish fauna, fuelling more than 40.0% of the biomass in four dominant fish species. The consumption rate of non-native bivalves by the native omnivorous fish Leporinus friderici suggested these filter-feeding organisms potentially constitute an important trophic connection between littoral consumers and pelagic energy sources. In addition, non-native prey were also prominent carbon sources for non-native fish, fuelling more than half of the biomass in peacock bass and silver croaker, suggesting these prey have a fundamental role in maintaining non-native fish populations in this system. Our results may help to understand fundamental ecological issues bringing to light the extent to which these new combinations of species influence the energy flow and ecosystem properties of the Volta Grande reservoir.
Congenitally athymic nude mice (nu/nu) and their phenotypically normal littermates (nu/+) were intraperitoneally infected with yeast cells of a strain of Paracoccidioides brasiliensis. The nude mice developed a severe and generalized infection with an intense parasitism of several organs, accompanied by a low-grade of tissue reaction. The lesions were characterized by abundant yeast-like cells of the fungus, and in some animals, numerous hyphal forms could be well visualized. In control animals, infection was moderate, almost exclusively restricted to the area of inoculation, and the lesions presented few parasites surrounded by an inflammatory response. Filamentous forms of the fungus were never encountered in these animals. 相似文献
A new steroidal saponin, 3-{(O-6-deoxy-a-L-mannopyranosyl-(1 --> 4)-O-beta-D-glucopyranosyl-(1 --> 3)-O-[O-beta-D-glucopyranosyl-(1 --> 3)-beta-D-glucopyranosyl-(1 --> 2)]-O-beta-D-glucopyranosyl-(1 --> 4)-beta-D-galactopyranosyl)oxy}-6-hydroxy-(3beta,5alpha,6alpha,25R)-spirostan-12-one, was isolated from Agave brittoniana Trel. The structure was determined by extensive NMR spectroscopy studies and chemical conversions. Its effects on the Na+-ATPase and (Na+ + K+)-ATPase activities of the proximal tubule from pig kidney were evaluated. It was observed that this steroidal saponin exerts a biphasic effect on the Na+-ATPase activity. It is concluded that the effect of the aqueous extract as a diuretic is due, at least in part, to the action of saponin on the ouabain-insensitive Na+-ATPase. 相似文献
Neurochemical Research - This study aimed to evaluate the effect of Cynara cardunculus leaf ethanol extract on inflammatory and oxidative stress parameters in the hypothalamus, prefrontal cortex,... 相似文献