La girolline, nouvelle substance antitumorale extraite de l'éponge, Pseudaxinyssa cantharella n. sp. (Axinellidae)

Une nouvelle substance antitumorale a été isolée d'une Eponge néo-calédonienne, #Pseudaxinyssa cantharella$. Sa structure a été établie à l'aide de ses caractéristiques spectrales et par préparation de dérivés sélectivement substitués. (Résumé d'auteur

NRT2.1 phosphorylation prevents root high affinity nitrate uptake activity in Arabidopsis thaliana

In Arabidopsis thaliana, NRT2.1 codes for a main component of the root nitrate high-affinity transport system. Previous studies revealed that post-translational regulation of NRT2.1 plays an important role in the control of root nitrate uptake and that one mechanism could correspond to NRT2.1 C-terminus processing. To further investigate this hypothesis, we produced transgenic plants with truncated forms of NRT2.1. It revealed an essential sequence for NRT2.1 activity, located between the residues 494-513. Using a phospho-proteomic approach, we found that this sequence contains one phosphorylation site, at serine 501, which can inactivate NRT2.1 function when mimicking the constitutive phosphorylation of this residue in transgenic plants. This phenotype could neither be explained by changes in abundance of NRT2.1 and NAR2.1, a partner protein of NRT2.1, nor by a lack of interaction between these two proteins. Finally, the relative level of serine 501 phosphorylation was found to be modulated by nitrate in wildtype plants. Altogether, these observations allowed us to propose a model for a new and essential mechanism for the regulation of NRT2.1 activity

Deep sequencing of the Mexican avocado transcriptome, an ancient angiosperm with a high content of fatty acids

Background: Avocado (Persea americana) is an economically important tropical fruit considered to be a good source of fatty acids. Despite its importance, the molecular and cellular characterization of biochemical and developmental processes in avocado is limited due to the lack of transcriptome and genomic information. Results: The transcriptomes of seeds, roots, stems, leaves, aerial buds and flowers were determined using different sequencing platforms. Additionally, the transcriptomes of three different stages of fruit ripening (pre-climacteric, climacteric and post-climacteric) were also analyzed. The analysis of the RNAseqatlas presented here reveals strong differences in gene expression patterns between different organs, especially between root and flower, but also reveals similarities among the gene expression patterns in other organs, such as stem, leaves and aerial buds (vegetative organs) or seed and fruit (storage organs). Important regulators, functional categories, and differentially expressed genes involved in avocado fruit ripening were identified. Additionally, to demonstrate the utility of the avocado gene expression atlas, we investigated the expression patterns of genes implicated in fatty acid metabolism and fruit ripening. Conclusions: A description of transcriptomic changes occurring during fruit ripening was obtained in Mexican avocado, contributing to a dynamic view of the expression patterns of genes involved in fatty acid biosynthesis and the fruit ripening process

GeneCloud Reveals Semantic Enrichment in Lists of Gene Descriptions

International audienceRevealing the over-represented functions in a particular gene list is a particular important post-genomic challenge. Genome-wide investigations generate gene lists from which meaningful information has to be extracted. This information is key to orient in planta investigations and to define the biological significance of genome-wide reprogramming. Here we describe the development and use of the GeneCloud algorithm, which retrieves the over-represented semantic terms in the description of a gene list

O-carboxyl- and N-methyltransferases active on plant aquaporins

present address : T. Sahr : UP Biologie des Bactéries Intracellulaires, Institut Pasteur, Paris, France; T. Adam : UMR Plante Microbe Environnement, Dijon, FranceInternational audienceMethylation of biologically active molecules is achieved by methyltransferases (MTases). MTases can act on proteins through N- or O-carboxylmethylation reactions. Methylation of lysine and glutamic acid residues was recently described on the N-terminal tail of AtPIP2;1, a plasma membrane aquaporin of plants. In this study, we combine a bioinformatic and a biochemical screen and identify two MTases of Arabidopsis thaliana, SDG7 (At2g44150) and OMTF3 (At3g61990), as acting on the N-terminal tail of AtPIP2;1, at Lys3 and Glu6, respectively. Confocal microscopy imaging showed the two enzymes to be associated with the endoplasmic reticulum. An in vitro assay using various AtPIP2;1 N-terminal peptides as a bait allowed characterization of the enzymatic properties of recombinant SDG7 and OMTF3. The two enzymes showed minimal apparent K(m) values for their substrates, S-adenosylmethionine and peptide, in the range of 5-8 and 2-9 M, respectively. SDG7 was shown to almost exclusively mono- or di-methylate Lys3. In contrast, OMTF3 specifically methylated Glu6, this methylation being dependent on the methylation profile of the neighboring Lys3 residue. In conclusion, this study allows the characterization of the first MTases able to methylate plant transmembrane proteins and provides the first identification of a glutamate-MTase in eukaryotes

Identification of ion channels expressed in Medicago truncatula root hairs

Identification of ion channels expressed in Medicago truncatula root hairs . 3rd Meeting on Molecular Mechanisms in Nitogen Fixing Root Endosymbiose

Genetic linkage of Meleda disease to chromosome 8qter

International audienc