Ectopic expression of PtaRHE1, encoding a poplar RING-H2 protein with E3 ligase activity, alters plant development and induces defence-related responses

RING (really interesting new gene)-H2 domain-containing proteins are widely represented in plants and play important roles in the regulation of many developmental processes as well as in plant–environment interactions. In the present report, experiments were performed to unravel the role of the poplar gene PtaRHE1, coding for a RING-H2 protein. In vitro ubiquitination assays indicate a functional E3 ligase activity for PtaRHE1 with the specific E2 ubiquitin-conjugating enzyme UbcH5a. The overexpression of PtaRHE1 in tobacco resulted in a pleiotropic phenotype characterized by a curling of the leaves, the formation of necrotic lesions on leaf blades, growth retardation, and a delay in floral transition. The plant gene expression response to PtaRHE1 overexpression provided evidence for the up-regulation of defence- and/or programmed cell death-related genes. Moreover, genes coding for WRKY transcription factors as well as for mitogen-activated protein kinases, such as wound-induced protein kinase (WIPK), were also found to be induced in the transgenic lines as compared with the wild type. In addition, histochemical β-glucuronidase staining showed that the PtaRHE1 promoter is induced by plant pathogens and by elicitors such as salicylic acid and cellulase. Taken together, these results suggest that the E3 ligase PtaRHE1 plays a role in the ubiquitination-mediated regulation of defence response, possibly by acting upstream of WIPK and/or in the activation of WRKY factors

Analysis of Genome Sequences from Plant Pathogenic Rhodococcus Reveals Genetic Novelties in Virulence Loci

Members of Gram-positive Actinobacteria cause economically important diseases to plants. Within the Rhodococcus genus, some members can cause growth deformities and persist as pathogens on a wide range of host plants. The current model predicts that phytopathogenic isolates require a cluster of three loci present on a linear plasmid, with the fas operon central to virulence. The Fas proteins synthesize, modify, and activate a mixture of growth regulating cytokinins, which cause a hormonal imbalance in plants, resulting in abnormal growth. We sequenced and compared the genomes of 20 isolates of Rhodococcus to gain insights into the mechanisms and evolution of virulence in these bacteria. Horizontal gene transfer was identified as critical but limited in the scale of virulence evolution, as few loci are conserved and exclusive to phytopathogenic isolates. Although the fas operon is present in most phytopathogenic isolates, it is absent from phytopathogenic isolate A21d2. Instead, this isolate has a horizontally acquired gene chimera that encodes a novel fusion protein with isopentyltransferase and phosphoribohydrolase domains, predicted to be capable of catalyzing and activating cytokinins, respectively. Cytokinin profiling of the archetypal D188 isolate revealed only one activate cytokinin type that was specifically synthesized in a fas-dependent manner. These results suggest that only the isopentenyladenine cytokinin type is synthesized and necessary for Rhodococcus phytopathogenicity, which is not consistent with the extant model stating that a mixture of cytokinins is necessary for Rhodococcus to cause leafy gall symptoms. In all, data indicate that only four horizontally acquired functions are sufficient to confer the trait of phytopathogenicity to members of the genetically diverse clade of Rhodococcus

Etude de l’interaction « Rhodococcus fascians »-plante: utilisation pour la régénération et la propagation de plantes

FRFC 2.4.565.00.F.info:eu-repo/semantics/publishe

Enzyme-Linked ImmunoSorbent Assay (ELISA) for the determination of free and conjugated tropine alkaloids in Datura stramonium extract from plant and hairy-root cultures

info:eu-repo/semantics/publishe

Utilisation des systèmes poison-antidote bactériens comme marqueur de sélection négative chez les végétaux supérieurs: application pour la transgenèse ciblée

FRFC 2.4.590.04.F.info:eu-repo/semantics/publishe

Analyse et identification de microARNs impliqués dans le développement de la galle feuillée chez Arabidopsis thaliana -- biologie moléculaire

Les microARNs sont de petits ARNs non codant impliqués dans la régulation négativede nombreuses voies métaboliques. Dans ce travail, leur rôle de régulateur est étudié dans lecadre de l’interaction plante-pathogène entre Arabidopsis thaliana et Rhodococcus fascians.En effet, de nombreuses études ont mis en évidence l’implication de cette bactérie dansl’établissement de déformations phénotypiques appelées « galles feuillées » chez la plante.Ces symptômes apparaissent à cause d’une modification de la balance hormonaleauxine/cytokinine de la plante par la bactérie.Le but de cette étude est de réaliser un screening sur une sélection de microARNsétablie par des recherches bioinformatiques, selon certains critères, et de tenter de mettre enévidence leur implication dans la perturbation de cette balance hormonale, via la régulationdes voies de signalisation auxiniques et cytokiniques de la plante, ainsi que dans lephénomène de maintenance des méristèmes.Pour ce faire, des plantules d’A. thaliana de 8 jours ont été infectées par trois souchesdifférentes de R. fascians :la D188, la D5 et la A44A. Nous avons extrait l’ARN de cesplantes après 14 dpi, et réalisé des expériences de RT-qPCR afin d’étudier l’expressionrelative des microARNs sélectionnés, en comparaison avec une plante saine. Cinq réplicasbiologiques de l’expérience ont été réalisés.Les résultats obtenus par RT-qPCR sont très hétérogènes d’un réplica à l’autre,probablement à cause d’une grande variabilité biologique. Cependant, par comparaison avecles phénotypes observés macroscopiquement chez les plantes infectées, pour les cinq réplicas,des tendances intéressantes ont pu être dégagées.En conclusion, nous avons pu montrer que certains microARNs sont impliqués dans larégulation des voies de signalisation des auxines ainsi que dans la maintenance desméristèmes. Par contre, aucune information ne nous permet de corréler la régulation par lesmicroARNs à une modification des voies de signalisation cytokiniques. De plus, l’étude apermi de mettre en évidence que la plante ne semble pas activer ses mécanismes de défense,médiés par les microARNs, lorsqu’elle est infectée par une souche virulente de R. fascians.info:eu-repo/semantics/nonPublishe

Impact of the phytopathogenic bacteria Rhodococcus fascians on tobacco BY-2 cell cycle progression

info:eu-repo/semantics/publishe

Communications chimiques induites lors des interactions plantes-microorganismes: altérations métaboliques chez la galle feuillée néoformée suite à une infection par Rhodococcus fascians

FRFC 2.4.593.09.F.info:eu-repo/semantics/publishe

From primary to secondary growth: origin and development of the vascular system

Vascular tissue differentiation is essential to enable plant growth and follows well-structured and complex developmental patterns. Based on recent data obtained from Arabidopsis and Populus, advances in the understanding of the molecular basis of vascular system development are reviewed. As identified by forward and/or reverse genetics, several gene families have been shown to be involved in the proliferation and identity of vascular tissues and in vascular bundle patterning. Although the functioning of primary meristems, for example the shoot apical meristem (SAM), is well documented in the literature, the genetic network that regulates (pro)cambium is still largely not deciphered. However, recent genome-wide expression analyses have identified candidate genes for secondary vascular tissue development. Of particular interest, several genes known to regulate the SAM have also been found to be expressed in the vascular cambium, highlighting possible overlapping regulatory mechanisms between these two meristems.Journal ArticleResearch Support, Non-U.S. Gov'tReviewinfo:eu-repo/semantics/publishe

Rhodococcus fascians - plant interaction: a novel biotechnological approach for plant propagation

info:eu-repo/semantics/publishe