L'organogènese inflorescentielle dans les bourgeons anticipés de vigne (Vitis vinifera L. cépage Pinot)

Organogenesis of inflorescences in the lateral buds of grapevine (Vitis vinifera L. cv. Pinot)The formation of inflorescences in lateral buds has been investigated by studies of longitudinal sections of paraffin-embedded lateral buds. The lateral buds at position 6 (from the base) were collected from non-decapitated shoots, from the middle of May to the end of June. The different developmental stages of inflorescence and also a chronological analysis have been described. The observations inform about the organogenetic ch aracteristics which occur in the absence of decapitation of the main shoot

Recovery of mutants impaired in pathogenicity after transposition of Impala in Fusarium oxysporum f. sp. melonis

The ability of transposon impala to inactivate genes involved in pathogenicity was tested in Fusarium oxysporum f. sp. melonis. Somatic excision of an impala copy inserted in the nitrate reductase-encoding niaD gene was positively selected through a phenotypic assay based on the restoration of nitrate reductase activity. Independent excision events were analyzed molecularly and shown to carry reinsertedimpala in more than 70% of the cases. Mapping of reinserted impala elements on large NotI-restriction fragments showed that impala transposes randomly. By screening 746 revertants on plants, a high proportion (3.5%) of mutants impaired in their pathogenic potential was recovered. According to the kinetics of wilt symptom development, the strains that were impaired in pathogenicity were clustered in three classes: class 1 grouped two strains that never induced Fusarium wilt symptoms on the host plant; class 2 and class 3 grouped 15 and 9 revertants which caused symptoms more than 50 and 30 days after inoculation, respectively. The first results demonstrate the efficiency of transposition in generating mutants affected in pathogenicity, which are usually difficult to obtain by classical mutagenesis, and open the possibility to clone the altered genes with impala as a tag

Exploring the evolutionary ecology of fungal endophytes in agricultural systems: using functional traits to reveal mechanisms in community processes

All plants, including crop species, harbor a community of fungal endophyte species, yet we know little about the biotic factors that are important in endophyte community assembly. We suggest that the most direct route to understanding the mechanisms underlying community assembly is through the study of functional trait variation in the host and its fungal consortium. We review studies on crop endophytes that investigate plant and fungal traits likely to be important in endophyte community processes. We focus on approaches that could speed detection of general trends in endophyte community assembly: (i) use of the ‘assembly rules’ concept to identify specific mechanisms that influence endophyte community dynamics, (ii) measurement of functional trait variation in plants and fungi to better understand endophyte community processes and plant–fungal interactions, and (iii) investigation of microbe–microbe interactions, and fungal traits that mediate them. This approach is well suited for research in agricultural systems, where pair-wise host–fungus interactions and mechanisms of fungal–fungal competition have frequently been described. Areas for consideration include the possibility that human manipulation of crop phenotype and deployment of fungal biocontrol species can significantly influence endophyte community assembly. Evaluation of endophyte assembly rules may help to fine-tune crop management strategies

The Nuclear Protein Sge1 of Fusarium oxysporum Is Required for Parasitic Growth

Dimorphism or morphogenic conversion is exploited by several pathogenic fungi and is required for tissue invasion and/or survival in the host. We have identified a homolog of a master regulator of this morphological switch in the plant pathogenic fungus Fusarium oxysporum f. sp. lycopersici. This non-dimorphic fungus causes vascular wilt disease in tomato by penetrating the plant roots and colonizing the vascular tissue. Gene knock-out and complementation studies established that the gene for this putative regulator, SGE1 (SIX Gene Expression 1), is essential for pathogenicity. In addition, microscopic analysis using fluorescent proteins revealed that Sge1 is localized in the nucleus, is not required for root colonization and penetration, but is required for parasitic growth. Furthermore, Sge1 is required for expression of genes encoding effectors that are secreted during infection. We propose that Sge1 is required in F. oxysporum and other non-dimorphic (plant) pathogenic fungi for parasitic growth

Instabilités liées à la longueur finie d'un plasma

We consider a system of two counterstreaming electron beams of finite length, including boundary conditions for both particles and waves. We describe a mechanism for instability with frequencies connected with the transit time of the particles in the configuration. The dispersion relation of these waves is discussed taking into account the parameters of the system (electron density, interaction length, velocity of the beams).En nous limitant au cas du système double faisceau et en introduisant des conditions aux limites, nous mettons en évidence l'existence d'instabilités liées au temps de transit des particules dans la configuration. Après avoir obtenu l'équation régissant ces ondes, nous étudions numériquement l'influence de chacun des paramètres (densité, longueur d'interaction, vitesse des faisceaux...)

GOR, the Group of Revolutionary Objects: Praxis and Research

GOR stands for Groupe des Objets Revolutionaires, or, in English, the Group of Revolutionary Objects. This group was founded by Filipe Pais, Julie Brugier and Olivain Porry in 2018, in reaction to two major planetary concerns: the climate crisis and techno-solutionism. GOR, in response, opens a fictional design space for debate and aesthetic manifestations, wherein objects and machines are given autonomy, and the possibility of disobeying whilst challenging human decisions. This article is a statement about GOR’s motivations, practice and research, written by two of the group members. In addition to further introducing the GOR manifesto and the forces which have given rise to it, it reviews its artistic practices and actions conducted during art residencies and group exhibitions; it identifies two examples of how the GOR design space can yield interesting clues in research, introducing the notion of super-object and an artistic framework named COCO2