Assessing the possible maintenance of TYLCV-satellite association. [O.21]

Viruses of the genus Begomovirus (Family Geminiviridae) are frequently detected with half genome size DNA molecules, either defective DNAs or satellite DNA (? or ?). Whereas some begomoviruses, like Tomato yellow leaf curl virus (TYLCV) were never detected with satellite DNAs, other begomoviruses, like Cotton leaf curl virus (CLCuV), depend upon a betasatellite for their infectivity. Besides the CLCuV-type begomoviruses which may be considered as bipartite begomoviruses, most of the begomoviruses detected with satellites were shown to be infective without their satellites. The alphasatellite was rarely proved to have any impact on the helper virus but the betasatellite was often shown to increase the virulence of its helper virus. Although satellites were never detected with TYLCV in natural conditions, TYLCV was reported as a helper virus for both satellites in artificial conditions and its virulence was dramatically increased when co-inoculated with betasatellites. We have confirmed these results with the Cotton leaf curl Gezira betasatellite (CLCuGB) and two alphasatellites, Cotton leaf curl Gezira alphasatellite (CLCuGA) and Okra leaf curl Burkina Faso alphasatellite (OLCA). If the co-infection of TYLCV and a betasatellite would occur in natural conditions, tomato production may be severely affected. As the probability of such a scenario mainly depends on the maintenance of TYLCV-satellite associations over time, we have studied various factors potentially determining this maintenance: (i) the relative intra-plant accumulation of TYLCV and the satellites, (ii) the cellular co-infection level of TYLCV and satellites, and (iv) the transmission efficiency of satellites by the vector Bemisia tabaci. These various factors were analyzed with CLCuGB, CLCuGA and OLCA. Besides the specific question of the possible maintenance of satellites with TYLCV, the results of our study are expected to provide a new insight on begomoviruses detected in co-infection with satellites in natural conditions, but which were proved to be infectious without satellites. (Résumé d'auteur

Utilisation du rendu expressif pour l'illustration et l'exploration de données archéologiques

National audienceLe rendu expressif est une branche relativement jeune de la synthèse d'images qui s'intéresse non pas à créer des images qui sont le résultat de simulations de phénomènes physiques réalistes, mais qui tend à communiquer visuellement des informations sur les objets représentés par le biais de styles variés (dessin, aquarelle, etc). Ce type de rendu semble particulièrement adapté au domaine de l'archéologie pour deux raisons : il permet d'illustrer les hypothèses de reconstruction 3D archéologiques sans pour autant biaiser l'interprétation par une représentation trop réaliste et peut aussi apporter une méthode visuelle intuitive d'exploration de données archéologiques. Dans cet exposé, nous allons tout d'abord présenter les travaux que nous avons réalisé par le passé portant sur la création d'illustrations (effets de papier, aquarelle). Puis nous allons introduire les aspects du rendu expressif qui permettraient l'exploration sémantique de données archéologiques

Improving Shape Depiction under Arbitrary Rendering

International audienceBased on the observation that shading conveys shape information through intensity gradients, we present a new technique called Radiance Scaling that modifies the classical shading equations to offer versatile shape depiction functionalities. It works by scaling reflected light intensities depending on both surface curvature and material characteristics. As a result, diffuse shading or highlight variations become correlated to surface feature variations, enhancing concavities and convexities. The first advantage of such an approach is that it produces satisfying results with any kind of material for direct and global illumination: we demonstrate results obtained with Phong and Ashikmin-Shirley BRDFs, Cartoon shading, sub-Lambertian materials, perfectly reflective or refractive objects. Another advantage is that there is no restriction to the choice of lighting environment: it works with a single light, area lights, and inter-reflections. Third, it may be adapted to enhance surface shape through the use of precomputed radiance data such as Ambient Occlusion, Prefiltered Environment Maps or Lit Spheres. Finally, our approach works in real-time on modern graphics hardware making it suitable for any interactive 3D visualization

Shading with Apparent Relief

SIGGRAPH '08: ACM SIGGRAPH 2008 talksInternational audienceShape depiction is an important dimension of image creation. For example, techniques are used to remove ambiguities in scientific illustrations, or to create more legible representations in paintings and drawings. Previous approaches focus on a set body of techniques: line-based rendering. Such techniques generate some shape cues to depict the object characteristics that correspond to discontinuities of shape features. Many artists rather depict an object's shape through shading. They have to use other kinds of shape cues that correspond to continuous variations of shape features to convey more subtle information about shape and integrate it seamlessly into conventional lighting. Instead of detecting sharp discontinuities as in line-based rendering, we thus seek a set of continuous cues that have to be defined for each pixel of an image. To this end, we introduce an intermediate representation that we call Apparent Relief to assist the user. It is a view-dependent shape descriptor, from which continuous shape cues are easily extracted, and which gives rise to stylized shading-based shape depictions. By construction, it is free of temporal coherence artifacts and naturally leads to automatic Levels-of-Detail (LOD) effects. Our approach is simple to implement, runs in real-time on modern graphics hardware, and allows a user selection of features. We illustrate its potential using several shading styles

Apparent relief: a shape descriptor for stylized shading

International audienceShape depiction in non-photorealistic rendering of 3D objects has mainly been concerned with the extraction of contour lines, which are generally detected by tracking the discontinuities of a given set of shape features varying on the surface and/or the picture plane. In this paper, we investigate another approach: the depiction of shape through shading. This technique is often used in scientific illustration, comics, cartoon animation and various other artwork. A common method consists in indirectly adapting light positions to reveal shape features; but it quickly becomes impractical when the complexity of the object augments. In contrast, our approach is to directly extract a set of shape cues that are easily manipulated by a user and re-introduced during shading. The main problem raised by such an approach is that shape cues must be identified in a continuous way in image space, as opposed to line-based techniques. Our solution is a novel view-dependent shape descriptor called Apparent Relief, which carries pertinent continuous shape cues for every pixel of an image. It consists of a combination of object- and image-space attributes. Such an approach provides appealing properties: it is simple to manipulate by a user, may be applied to a vast range of styles, and naturally brings levels-of-detail functionalities. It is also simple to implement, and works in real-time on modern graphics hardware

Role of a short non coding viral sequence in bypassing crossprotection in tomato infecting begomoviruses

TYLCV-IS76 (IS76) is a natural recombinant of Tomato Yellow Curl Virus (TYLCV, Begomovirus, Geminiviridae) in which 76 nucleotides (nts) of the intergenic region (S76) have been replaced by the homologous sequence from Tomato Yellow Curl Sardinia Virus (TYLCSaV). We monitored the emergence of IS76 in Morocco and showed, in controlled conditions, that its intra-plant accumulation was significantly higher than those of parental viruses in resistant cultivars carrying the Ty-1 resistance gene. This gene is known to code for a γ-clade RNA-dependent RNA polymerase that prevents symptoms and reduces viral load. The competitive advantage of IS76 is detected irrespective of co- infection conditions, simultaneously with parents or 1 or 4 months after parents, which questioned the existence of crossprotection with TYLCV and more generally with begomoviruses. Using TYLCV variants differing by 8 or 30 nts within the S76 region and qPCR monitoring of viral DNA accumulations, we proved the existence of a crossprotection phenomenon with the TYLCV parent, in Ty-1-resistant and susceptible tomato plants, and in turn that IS76 escapes this mechanism. Although crossprotection mechanisms with TYLCV are not yet known, we studied the genetic determinism of the crossprotection-escape and more specifically whether it is determined only by the S76 region. It this is true, the escape would be observed with the TYLCSaV parent, the donor of S76, and also with any other begomovirus that inherit S76 by recombination. A TYLCSaV mutant and a recombinant Tomato leaf curl Comoros virus (ToLCKMV) carrying S76 were engineered to test this hypothesis. Results will be discussed in relation with the emergence of IS76 and more generally with the crossprotection phenomenon in begomoviruses and its potential application in their management

Radiance Scaling for Versatile Surface Enhancement

International audienceWe present a novel technique called Radiance Scaling for the depiction of surface shape through shading. It adjusts reflected light intensities in a way dependent on both surface curvature and material characteristics. As a result, diffuse shading or highlight variations become correlated to surface feature variations, enhancing surface concavities and convexities. This approach is more versatile compared to previous methods. First, it produces satisfying results with any kind of material: we demonstrate results obtained with Phong and Ashikmin BRDFs, Cartoon shading, sub-Lambertian materials, and perfectly reflective or refractive objects. Second, it imposes no restriction on lighting environment: it does not require a dense sampling of lighting directions and works even with a single light. Third, it makes it possible to enhance surface shape through the use of precomputed radiance data such as Ambient Occlusion, Prefiltered Environment Maps or Lit Spheres. Our novel approach works in real-time on modern graphics hardware and is faster than previous techniques

SIAMESE-RELATED1 Is Regulated Posttranslationally and Participates in Repression of Leaf Growth under Moderate Drought.

The plant cell cycle is tightly regulated by factors that integrate endogenous cues and environmental signals to adapt plant growth to changing conditions. Under drought, cell division in young leaves is blocked by an active mechanism, reducing the evaporative surface and conserving energy resources. The molecular function of cyclin-dependent kinase-inhibitory proteins (CKIs) in regulating the cell cycle has already been well studied, but little is known about their involvement in cell cycle regulation under adverse growth conditions. In this study, we show that the transcript of the CKI gene SIAMESE-RELATED1 (SMR1) is quickly induced under moderate drought in young Arabidopsis thaliana leaves. Functional characterization further revealed that SMR1 inhibits cell division and affects meristem activity, thereby restricting the growth of leaves and roots. Moreover, we demonstrate that SMR1 is a short-lived protein that is degraded by the 26S proteasome after being ubiquitinated by a Cullin-RING E3 ubiquitin ligase. Consequently, overexpression of a more stable variant of the SMR1 protein leads to a much stronger phenotype than overexpression of the native SMR1. Under moderate drought, both the SMR1 transcript and SMR1 protein accumulate. Despite this induction, smr1 mutants do not show overall tolerance to drought stress but do show less growth inhibition of young leaves under drought. Surprisingly, the growth-repressive hormone ethylene promotes SMR1 induction, but the classical drought hormone abscisic acid does not

PHENOPSIS DB: an Information System for Arabidopsis thaliana phenotypic data in an environmental context

<p>Abstract</p> <p>Background</p> <p>Renewed interest in plant × environment interactions has risen in the post-genomic era. In this context, high-throughput phenotyping platforms have been developed to create reproducible environmental scenarios in which the phenotypic responses of multiple genotypes can be analysed in a reproducible way. These platforms benefit hugely from the development of suitable databases for storage, sharing and analysis of the large amount of data collected. In the model plant <it>Arabidopsis thaliana</it>, most databases available to the scientific community contain data related to genetic and molecular biology and are characterised by an inadequacy in the description of plant developmental stages and experimental metadata such as environmental conditions. Our goal was to develop a comprehensive information system for sharing of the data collected in PHENOPSIS, an automated platform for <it>Arabidopsis thaliana </it>phenotyping, with the scientific community.</p> <p>Description</p> <p>PHENOPSIS DB is a publicly available (URL: <url>http://bioweb.supagro.inra.fr/phenopsis/</url>) information system developed for storage, browsing and sharing of online data generated by the PHENOPSIS platform and offline data collected by experimenters and experimental metadata. It provides modules coupled to a Web interface for (i) the visualisation of environmental data of an experiment, (ii) the visualisation and statistical analysis of phenotypic data, and (iii) the analysis of <it>Arabidopsis thaliana </it>plant images.</p> <p>Conclusions</p> <p>Firstly, data stored in the PHENOPSIS DB are of interest to the <it>Arabidopsis thaliana </it>community, particularly in allowing phenotypic meta-analyses directly linked to environmental conditions on which publications are still scarce. Secondly, data or image analysis modules can be downloaded from the Web interface for direct usage or as the basis for modifications according to new requirements. Finally, the structure of PHENOPSIS DB provides a useful template for the development of other similar databases related to genotype × environment interactions.</p