Insights from the genome of the biotrophic fungal plant pathogen Ustilago maydis

Ustilago maydis is a ubiquitous pathogen of maize and a well-established model organism for the study of plant-microbe interactions. This basidiomycete fungus does not use aggressive virulence strategies to kill its host. U. maydis belongs to the group of biotrophic parasites (the smuts) that depend on living tissue for proliferation and development. Here we report the genome sequence for a member of this economically important group of biotrophic fungi. The 20.5-million-base U. maydis genome assembly contains 6,902 predicted protein-encoding genes and lacks pathogenicity signatures found in the genomes of aggressive pathogenic fungi, for example a battery of cell-wall-degrading enzymes. However, we detected unexpected genomic features responsible for the pathogenicity of this organism. Specifically, we found 12 clusters of genes encoding small secreted proteins with unknown function. A significant fraction of these genes exists in small gene families. Expression analysis showed that most of the genes contained in these clusters are regulated together and induced in infected tissue. Deletion of individual clusters altered the virulence of U. maydis in five cases, ranging from a complete lack of symptoms to hypervirulence. Despite years of research into the mechanism of pathogenicity in U. maydis, no 'true' virulence factors had been previously identified. Thus, the discovery of the secreted protein gene clusters and the functional demonstration of their decisive role in the infection process illuminate previously unknown mechanisms of pathogenicity operating in biotrophic fungi. Genomic analysis is, similarly, likely to open up new avenues for the discovery of virulence determinants in other pathogens. ©2006 Nature Publishing Group.J.K., M. B. and R.K. thank G. Sawers and U. Kämper for critical reading of the manuscript. The genome sequencing of Ustilago maydis strain 521 is part of the fungal genome initiative and was funded by National Human Genome Research Institute (USA) and BayerCropScience AG (Germany). F.B. was supported by a grant from the National Institutes of Health (USA). J.K. and R.K. thank the German Ministry of Education and Science (BMBF) for financing the DNA array setup and the Max Planck Society for their support of the manual genome annotation. F.B. was supported by a grant from the National Institutes of Health, B.J.S. was supported by the Natural Sciences and Engineering Research Council of Canada and the Canada Foundation for Innovation, J.W.K. received funding from the Natural Sciences and Engineering Research Council of Canada, J.R.-H. received funding from CONACYT, México, A.M.-M. was supported by a fellowship from the Humboldt Foundation, and L.M. was supported by an EU grant. Author Contributions All authors were involved in planning and executing the genome sequencing project. B.W.B., J.G., L.-J.M., E.W.M., D.D., C.M.W., J.B., S.Y., D.B.J., S.C., C.N., E.K., G.F., P.H.S., I.H.-H., M. Vaupel, H.V., T.S., J.M., D.P., C.S., A.G., F.C. and V. Vysotskaia contributed to the three independent sequencing projects; M.M., G.M., U.G., D.H., M.O. and H.-W.M. were responsible for gene model refinement, database design and database maintenance; G.M., J. Kämper, R.K., G.S., M. Feldbrügge, J.S., C.W.B., U.F., M.B., B.S., B.J.S., M.J.C., E.C.H.H., S.M., F.B., J.W.K., K.J.B., J. Klose, S.E.G., S.J.K., M.H.P., H.A.B.W., R.deV., H.J.D., J.R.-H., C.G.R.-P., L.O.-C., M.McC., K.S., J.P.-M., J.I.I., W.H., P.G., P.S.-A., M. Farman, J.E.S., R.S., J.M.G.-P., J.C.K., W.L. and D.H. were involved in functional annotation and interpretation; T.B., O.M., L.M., A.M.-M., D.G., K.M., N.R., V. Vincon, M. VraneŠ, M.S. and O.L. performed experiments. J. Kämper, R.K. and M.B. wrote and edited the paper with input from L.-J.M., J.G., F.B., J.W.K., B.J.S. and S.E.G. Individual contributions of authors can be found as Supplementary Notes

Essais de fragmentation en compression sur des systemes fibre de carbone/matrice organique

Tire de : Comptes rendus des 8e Journees Nationales sur les Composites, Palaiseau (France), 16-18 novembre 1992Available at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1992 n.216 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Strong polarization dependent nonlinear excitation of a perovskite nanocrystal monolayer on a chiral dielectric nanoantenna array

With their unique optoelectronic properties, perovskite nanocrystals are highly advantageous semiconductor materials for tailored light applications including an interaction with circularly polarized light. Although chiral perovskite nanocrystals have been obtained by the adsorption of chiral molecules, their chiroptical response is still intrinsically weak. Alternatively, perovskites have been combined with artificial chiral surfaces demonstrating enhanced chiroptical responses. However, bulk perovskite films of considerable thickness were required, mitigating the perovskite’s photoluminescence efficiency and processability. Here we developed a hybrid system of a dielectric chiral nanoantenna array that was coated with a monolayer of cubic all-inorganic lead halide perovskite nanocrystals. By tuning the thickness of the perovskite film down to one monolayer of nanocrystals, we restricted the interactions exclusively to the near-field regime. The chiral surface built of z-shaped Si nanoantennas features pronounced chiral resonances in the visible to IR region. We demonstrate that the two-photon excited photoluminescence emission of the nanocrystals can be enhanced by up to one order of magnitude in this configuration. This emission increase is controllable by the choice of the excitation wavelength and polarization with an asymmetry in emission of up to 25% upon left and right circularly polarized illumination. Altogether, our findings demonstrate a pathway to an all-optical control and modulation of perovskite light emission via strong polarization sensitive light–matter interactions in the near-field, rendering this hybrid system interesting for sensing and display technologies