Diet of arbuscular mycorrhizal fungi: bread and butter ?

Most plants entertain mutualistic interactions known as arbuscular mycorrhiza (AM) with soil fungi (Glomeromycota) which provide them with mineral nutrients in exchange for reduced carbon from the plant. Mycorrhizal roots represent strong carbon sinks in which hexoses are transferred from the plant host to the fungus. However, most of the carbon in AM fungi is stored in the form of lipids. The absence of the type I fatty acid synthase (FAS-I) complex from the AM fungal model species Rhizophagus irregularis suggests that lipids may also have a role in nutrition of the fungal partner. This hypothesis is supported by the concerted induction of host genes involved in lipid metabolism. We explore the possible roles of lipids in the light of recent literature on AM symbiosis

The rise and fall of a secondary policy: la Joyanca (Guatemala)

International audiencePaleoenvironmental studies have recently made impressive contributions to our understanding of the Maya Lowland Terminal Classic crisis. They put much emphasis on the detection of drought episodes during the ninth century and later. There is no doubt that such events had an impact on Maya sociopolitical dynamics, although ninth-century droughts may have entailed relatively moderate rainfall reduction.Not only Maya agriculture but also urban populations were vulnerable to variation in precipitation.Moreover, the impact of reconstructed climatic events does not appear to have been as direct and synchronous as we would expect, and the concatenation of environmental and sociopolitical factors remains poorly investigated

Modélisation pharmacocinétique/pharmacodynamique par une approche de population de l'effet du G-CSF chez des patients traités avec du carboplatine

Une des stratégies pour limiter les neutropénies induites par la chimiothérapie est l utilisation de granulocyte-colony stimulating factor (G-CSF). Nous avons développé, par une approche de population, un nouveau modèle pharmacocinétique/pharmacodynamique capable de décrire la cinétique des neutrophiles des patients traités au carboplatine, qu ils aient ou non reçu du G-CSF. Les simulations réalisées à partir de ce modèle ont montré que le G-CSF n était pas bénéfique chez tous les patients et que la formulation à action longue semblerait plus efficace que les autres formulations. Nous avons également établi des règles de décision permettant d une part de prédire le risque de neutropénie sévère, et d autre part d identifier précocement les patients pour lesquels le G-CSF peut avoir un effet bénéfique.Granulocyte colony-stimulating factor (G-CSF) is often used in cancer patients receiving cytotoxic drugs to prevent or reduce high grade neutropenia. We developed a new population pharmacokinetic/pharmacodynamic model to describe neutrophil time-course in carboplatin-treated patients, whether or not they received G-CSF. Model simulations showed that G-CSF was not as beneficial as expected in some patients and that the onceper- cycle formulation was more efficient than other formulations. Model-based decision rules were also built to anticipate prolonged high grade neutropenia and early identify patients for whom G-CSF was beneficial.TOULOUSE-INP (315552154) / SudocSudocFranceF

La cavité buccale et la femme enceinte

peer reviewe

The homology of odontodes in gnathostomes: insights from Dlx gene expression in the dogfish, Scyliorhinus canicula

<p>Abstract</p> <p>Background</p> <p>Teeth and tooth-like structures, together named odontodes, are repeated organs thought to share a common evolutionary origin. These structures can be found in gnathostomes at different locations along the body: oral teeth in the jaws, teeth and denticles in the oral-pharyngeal cavity, and dermal denticles on elasmobranch skin. We, and other colleagues, had previously shown that teeth in any location were serially homologous because: i) pharyngeal and oral teeth develop through a common developmental module; and ii) the expression patterns of the <it>Dlx </it>genes during odontogenesis were highly divergent between species but almost identical between oral and pharyngeal dentitions within the same species. Here we examine <it>Dlx </it>gene expression in oral teeth and dermal denticles in order to test the hypothesis of serial homology between these odontodes.</p> <p>Results</p> <p>We present a detailed comparison of the first developing teeth and dermal denticles (caudal primary scales) of the dogfish (<it>Scyliorhinus canicula</it>) and show that both odontodes develop through identical stages that correspond to the common stages of oral and pharyngeal odontogenesis. We identified six <it>Dlx </it>paralogs in the dogfish and found that three showed strong transcription in teeth and dermal denticles (<it>Dlx3</it>, <it>Dlx4 </it>and <it>Dlx5</it>) whereas a weak expression was detected for <it>Dlx1 </it>in dermal denticles and teeth, and for <it>Dlx2 </it>in dermal denticles. Very few differences in <it>Dlx </it>expression patterns could be detected between tooth and dermal denticle development, except for the absence of <it>Dlx2 </it>expression in teeth.</p> <p>Conclusions</p> <p>Taken together, our histological and expression data strongly suggest that teeth and dermal denticles develop from the same developmental module and under the control of the same set of <it>Dlx </it>genes. Teeth and dermal denticles should therefore be considered as serial homologs developing through the initiation of a common gene regulatory network (GRN) at several body locations. This mechanism of heterotopy supports the 'inside and out' model that has been recently proposed for odontode evolution.</p

A petunia GRAS transcription factor controls symbiotic gene expression and fungal morphogenesis in arbuscular mycorrhiza

Arbuscular mycorrhiza (AM) is a mutual symbiosis that involves a complex symbiotic interface over which nutrients are exchanged between the plant host and the AM fungus. Dozens of genes in the host are required for the establishment and functioning of the interaction, among them nutrient transporters that mediate the uptake of mineral nutrients delivered by the fungal arbuscules. We have isolated in a genetic mutant screen a petunia GRAS-type transcription factor, ATYPICAL ARBUSCULE (ATA), that acts as the central regulator of AM-related genes and is required for the morphogenesis of arbuscules. Forced mycorrhizal inoculations from neighbouring wild type plants revealed an additional role of ATA in restricting mycorrhizal colonization of the root meristem. The lack of ATA, which represents the orthologue of RAM1 in Medicago truncatula, renders the interaction completely ineffective, hence demonstrating the central role of AM-related genes for arbuscule development and function