Evidence for folate-salvage reactions in plants

Folates in vivo undergo oxidative cleavage, giving pterin and p-aminobenzoylglutamate (pABAGlu) moieties. These breakdown products are excreted in animals, but their fate is unclear in microorganisms and unknown in plants. As indirect evidence from this and previous studies strongly suggests that plants can have high folate-breakdown rates (approximately 10% per day), salvage of the cleavage products seems likely. Four sets of observations support this possibility. First, cleavage products do not normally accumulate: pools of pABAGlu (including its polyglutamyl forms) are equivalent to, at most, 4-14% of typical total folate pools in Arabidopsis thaliana, Lycopersicon esculentum and Pisum sativum tissues. Pools of the pterin oxidation end-product pterin-6-carboxylate are, likewise, fairly small (3-37%) relative to total folate pools. Second, little pABAGlu built up in A. thaliana plantlets when net folate breakdown was induced by blocking folate synthesis with sulfanilamide. Third, A. thaliana and L. esculentum tissues readily converted supplied breakdown products to folate synthesis precursors: pABAGlu was hydrolysed to p-aminobenzoate and glutamate, and dihydropterin-6-aldehyde was reduced to 6-hydroxymethyldihydropterin. Fourth, both these reactions were detected in vitro; the reduction used NADPH as cofactor. An alternative salvage route for pABAGlu, direct reincorporation into dihydrofolate via the action of dihydropteroate synthase, appears implausible from the properties of this enzyme. We conclude that plants are excellent organisms in which to explore the biochemistry of folate salvage

Integrative Identification of Arabidopsis Mitochondrial Proteome and Its Function Exploitation through Protein Interaction Network

Mitochondria are major players on the production of energy, and host several key reactions involved in basic metabolism and biosynthesis of essential molecules. Currently, the majority of nucleus-encoded mitochondrial proteins are unknown even for model plant Arabidopsis. We reported a computational framework for predicting Arabidopsis mitochondrial proteins based on a probabilistic model, called Naive Bayesian Network, which integrates disparate genomic data generated from eight bioinformatics tools, multiple orthologous mappings, protein domain properties and co-expression patterns using 1,027 microarray profiles. Through this approach, we predicted 2,311 candidate mitochondrial proteins with 84.67% accuracy and 2.53% FPR performances. Together with those experimental confirmed proteins, 2,585 mitochondria proteins (named CoreMitoP) were identified, we explored those proteins with unknown functions based on protein-protein interaction network (PIN) and annotated novel functions for 26.65% CoreMitoP proteins. Moreover, we found newly predicted mitochondrial proteins embedded in particular subnetworks of the PIN, mainly functioning in response to diverse environmental stresses, like salt, draught, cold, and wound etc. Candidate mitochondrial proteins involved in those physiological acitivites provide useful targets for further investigation. Assigned functions also provide comprehensive information for Arabidopsis mitochondrial proteome

A Functional Phylogenomic View of the Seed Plants

A novel result of the current research is the development and implementation of a unique functional phylogenomic approach that explores the genomic origins of seed plant diversification. We first use 22,833 sets of orthologs from the nuclear genomes of 101 genera across land plants to reconstruct their phylogenetic relationships. One of the more salient results is the resolution of some enigmatic relationships in seed plant phylogeny, such as the placement of Gnetales as sister to the rest of the gymnosperms. In using this novel phylogenomic approach, we were also able to identify overrepresented functional gene ontology categories in genes that provide positive branch support for major nodes prompting new hypotheses for genes associated with the diversification of angiosperms. For example, RNA interference (RNAi) has played a significant role in the divergence of monocots from other angiosperms, which has experimental support in Arabidopsis and rice. This analysis also implied that the second largest subunit of RNA polymerase IV and V (NRPD2) played a prominent role in the divergence of gymnosperms. This hypothesis is supported by the lack of 24nt siRNA in conifers, the maternal control of small RNA in the seeds of flowering plants, and the emergence of double fertilization in angiosperms. Our approach takes advantage of genomic data to define orthologs, reconstruct relationships, and narrow down candidate genes involved in plant evolution within a phylogenomic view of species' diversification

« Latin biblique et latin chrétien : quelques réflexions sur l’usage du texte biblique dans une recherche sémantique sur le latin des auteurs chrétiens »

Présentation lors du séminaire Biblindex de l’Institut des Sources Chrétiennes

Esme Stuart d'Aubigny, 1st Duke of Lennox c.1542-1583: a French courtier in Scotland

This thesis is a study of the life and careers of Esmé Stuart d’Aubigny, First Duke of Lennox, from his birth in the early 1540s to his death in May 1583, providing discussion of his legacy through his descendants. This study presents an understanding, within the context of the European religious conflicts of the second half of the sixteenth century, how a modest French lord became the most important noble in Scotland between 1579 and 1582. Esmé Stuart d’Aubigny was an influential person during the first years of James VI’s personal reign, notable for being a favourite of the Scottish king and for giving rise, in both Scotland and England, to fear of a new Catholic and French influence. Although he has been studied as the favourite of James VI, studies remained limited on his life in France before 1579, his involvement in a Catholic and European wide plot and his broader legacy. To ensure a higher level of knowledge of this French courtier, this work examines his family background and his education to understand whether his affiliation with the Stewart family was an important factor in his Scottish career. A study of his years in the service of France and his network, including the Valois brothers and the Guises, is also conducted to establish whether his years in France were properly formative. His career in Scotland from 1579 to 1582 are discussed in terms of three perspectives: royal favour, nobility and power, and the defence of the Catholic faith. Finally, his fall and legacy are questioned. This study offers new perspectives on Esmé Stuart d’Aubigny’s life, first by considering this matter using a biographical methodology, and, secondly, by changing the perspective on the second half of the sixteenth century to consider the individual of Esmé Stuart. By addressing gaps in the existing literature – notably using unpublished sources – this work presents the portrait of a French noble man who was not only destined to become the most important noble of the Scottish kingdom from 1579 to 1582 but who, thanks to his frequenting of the French court, become particularly socially intelligent and an opportunist with the ability to manipulate his surroundings to enable him to ascend within the most private royal circles

Sanctus et sanctitas dans les Bibles latines

Sancio, sanctus et sanctitas sont employés dans la Vulgate pour traduire des lexèmes hébreux et grecs appartenant au vocabulaire de la religion. Que traduisent exactement ces termes ? De quels sens se chargent-ils ? Quelles sont les évolutions sémantiques des lexèmes ?Sancio, sanctus and sanctitas are used in the Vulgate as translations of Hebrew and Greek lexemes that belong to religious vocabulary. What notions and actions do these terms exactly translate ? What new meanings do they carry ? How do the lexemes evolve semantically

: Sancio, sanctus et sanctitas sont employés dans la Vulgate pour traduire des lexèmes hébreux et grecs appartenant au vocabulaire de la religion. Que traduisent exactement ces termes ? De quels sens se chargent-ils ? Quelles sont les évolutions sémantiques des lexèmes ?

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