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Summary: T‐DNA transfer from Agrobacterium to its host plant genome relies on multiple interactions between plant proteins and bacterial effectors. One such plant protein is the Arabidopsis VirE2 interacting protein (AtVIP1), a transcription factor that binds Agrobacterium tumefaciens C58 VirE2, potentially acting as an adaptor between VirE2 and several other host factors. It remains unknown, however, whether the same VirE2 protein has evolved to interact with multiple VIP1 homologues in the same host, and whether VirE2 homologues encoded by different bacterial strains/species recognize AtVIP1 or its homologues. Here, we addressed these questions by systematic analysis (using the yeast two‐hybrid and co‐immunoprecipitation approaches) of interactions between VirE2 proteins encoded by four major representatives of known bacterial species/strains with functional T‐DNA transfer machineries and eight VIP1 homologues from Arabidopsis and tobacco. We also analysed the determinants of the VirE2 sequence involved in these interactions. These experiments showed that the VirE2 interaction is degenerate: the same VirE2 protein has evolved to interact with multiple VIP1 homologues in the same host, and different and mutually independent VirE2 domains are involved in interactions with different VIP1 homologues. Furthermore, the VIP1 functionality related to the interaction with VirE2 is independent of its function as a transcriptional regulator. These observations suggest that the ability of VirE2 to interact with VIP1 homologues is deeply ingrained into the process of Agrobacterium infection. Indeed, mutations that abolished VirE2 interaction with AtVIP1 produced no statistically significant effects on interactions with VIP1 homologues or on the efficiency of genetic transformation. [ABSTRACT FROM AUTHOR]

In the framework of the EUROfusion DEMO project, design studies for the tokamak magnet systems are conducted across several European institutions. Superconducting magnets are required to generate the high magnetic fields needed for the plasma confinement and control. The reference conductor design is based on Cable-In-Conduit Conductors (CICC) cooled at cryogenic temperatures by forced circulation of supercritical helium. The proposed Toroidal Field (TF) coils Winding Pack (WP) design should satisfy the design/safety criteria during operation (e.g., minimal temperature margin) and in off-normal conditions (e.g., hotspot temperature). Quenches are studied to ensure that the proposed conductor design and associated quench protection system guarantee the integrity of the magnet; such events are a safety and investment protection issue, and as such deserve high levels of scrutiny. Quench propagation in a coil is a 3-dimensional (3D) problem. For this reason, a transient pseudo-3D modeling tool was developed for coupled thermal and thermo-hydraulic calculation in a tokamak superconducting coil. The coupling tool is based on a 1D model of the cable using the THEA code, considering current distribution, helium flow, thermal conduction in the strands and propagation of the quench along the conductor; the 2D transverse thermal diffusion across turns is modeled using the Cast3M code, considering the conductor jacket and insulation, on a selected set of cross-sections along the coil. The aim of the analysis is to assess the quench behavior of the CEA proposal for DEMO TF coil. The hotspot temperatures as well as the propagation of the normal zone along the conductor length are evaluated in a realistic quench scenario, taking into account the impact of transverse heat diffusion. [ABSTRACT FROM AUTHOR]

Several genes in the Agrobacterium tumefaciens transferred (T)- DNA encode proteins that are involved in developmental alterations, leading to the formation of tumours in infected plants. We investigated the role of the protein encoded by the Atu6002 gene, the function of which is completely unknown. Atu6002 expression occurs in Agrobacterium-induced tumours, and is also activated on activation of plant cell division by growth hormones. Within the expressing plant cells, the Atu6002 protein is targeted to the plasma membrane. Interestingly, constitutive ectopic expression of Atu6002 in transgenic tobacco plants leads to a severe developmental phenotype characterized by stunted growth, shorter internodes, lanceolate leaves, increased branching and modified flower morphology. These Atu6002-expressing plants also display impaired response to auxin. However, auxin cellular uptake and polar transport are not significantly inhibited in these plants, suggesting that Atu6002 interferes with auxin perception or signalling pathways. [ABSTRACT FROM AUTHOR]

One the most intriguing, yet least studied, aspects of the bacterium-host plant interaction is the role of the host ubiquitin/proteasome system (UPS) in the infection process. Increasing evidence indicates that pathogenic bacteria subvert the host UPS to facilitate infection. Although both mammalian and plant bacterial pathogens are known to use the host UPS, the first prokaryotic F-box protein, an essential component of UPS, was identified in Agrobacterium. During its infection, which culminates in genetic modification of the host cell, Agrobacterium transfers its T-DNA—as a complex (T-complex) with the bacterial VirE2 and host VIP1 proteins—into the host cell nucleus. There the T-DNA is uncoated from its protein components before undergoing integration into the host genome. It has been suggested that the host UPS mediates this uncoating process, but there is no evidence indicating that this activity can unmask the T-DNA molecule. Here we provide support for the idea that the plant UPS uncoats synthetic T-complexes via the Skp1/Cullin/F-box protein VBF pathway and exposes the T-DNA molecule to external enzymatic activity. [ABSTRACT FROM AUTHOR]