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

Communications inter-règnes dans les interactions plantes-microorganismes

info:eu-repo/semantics/nonPublishe

Les microARNs: biogenèse, fonctionnement et rôles de ces nouveaux interrupteurs moléculaires

info:eu-repo/semantics/nonPublishe

Molecular bases of the Rhodococcus fascians - plant interaction :bacterial signal molecules and early plant gene responses

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Le Cylce Cellulaire chez les Plantes

info:eu-repo/semantics/nonPublishe

Rhéostats moléculaires: les miRNAs et les siRNAs, ou comment réguler l’expression des protéines avec des petits ARNs

info:eu-repo/semantics/nonPublishe

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

La coopération universitaire, ou comment réunir le Sud et le Nord pour atteindre le quorum afin de mener des recherches de pointe

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