Involvement of horizontal gene transfer in the emergence of new pathotypes of Ralstonia solanacearum : [Abstract of poster]

Ralstonia solanacearum is a widely distributed phytopathogenic bacterium that is known to invade more than 200 host species, mainly in tropical areas. R. solanacearum has been described as a highly flexible organism capable of counteracting plant resistance, leading to the emergence of a new pathological variant. We propose to investigate the fundamental role of horizontal gene transfer (HGT) in its genome evolution. In the R. solanacearum species complex, the natural ability to transform has been described as an ubiquitous physiological trait. Eighty percent of strains distributed in all phylotypes - likely species - have the ability to acquire free plasmids and/or genomic DNA (Coupat et al., 2008, FEMS Microbiol Ecol 66:14-24). Extent and number of transfer events were also evaluated by using selective antibiotics markers as well as by comparative genomic hybridization with DNA microarrays. Results showed that replacements might involve DNA fragments up to 90 kb and multiple integration events into the R. solanacearum genome. In addition, inter-phylotype HGT studies showed that transformants were able to acquire large DNA blocks (30 kb) containing pathogenicity determinants from the DNA donor (Guidot et al., 2009, ISME J. doi :1038/ismej.2009.14). The natural transformation mechanism thus appears as one of the main forces for the generation of emergent pathogens. We confirmed that a recombinant strain, which was found to be more virulent on tomato than its wild type parental strain, has acquired a type III effector which was not present in the wild type parental genome. (Texte intégral

Protection du patrimoine audiovisuel (La)

Assemblée nationale - Rapport fait au nom de la commission des Affaires étrangères sur le projet de loi n° 1893, autorisant l\u27approbation de la convention européenne relative à la protection du patrimoine audiovisuel et de son protocole sur la protection des productions télévisuelles

On the Probabilistic Query Complexity of Transitively Symmetric Problems

We obtain optimal lower bounds on the nonadaptive probabilistic query complexity of a class of problems defined by a rather weak symmetry condition. In fact, for each problem in this class, given a number T of queries we compute exactly the performance (i.e., the probability of success on the worst instance) of the best nonadaptive probabilistic algorithm that makes T queries. We show that this optimal performance is given by a minimax formula involving certain probability distributions. Moreover, we identify two classes of problems for which adaptivity does not help. We illustrate these results on a few natural examples, including unordered search, Simon's problem, distinguishing one-to-one functions from two-to-one functions, and hidden translation. For these last three examples, which are of particular interest in quantum computing, the recent theorems of Aaronson, of Laplante and Magniez, and of Bar-Yossef, Kumar and Sivakumar on the probabilistic complexity of black-box problems do not yield any nonconstant lower bound

Meridional Circulation During the Extended Solar Minimum: Another Component of the Torsional Oscillation?

We show here a component of the meridional circulation developing at medium-high latitudes (40-50 degrees) before the new solar cycle starts. Like the torsional oscillation of the zonal flows, this extra circulation seems to precede the onset of magnetic activity at the solar surface and move slowly towards lower latitudes. However, the behavior of this component differs from that of the torsional oscillation regarding location and convergence towards the equator at the end of the cycle. The observation of this component before the magnetic regions appear at the solar surface has only been possible due to the prolonged solar minimum. The results could settle the discussion as to whether the extra component of the meridional circulation around the activity belts, which has been known for some time, is or is not an effect of material motions around the active regions.Comment: ApJ Letters (accepted