Hormonal and transcriptional profiles highlight common and differential host responses to arbuscular mycorrhizal fungi and the regulation of the oxylipin pathway

Arbuscular mycorrhizal (AM) symbioses are mutualistic associations between soil fungi and most vascular plants. The symbiosis significantly affects the host physiology in terms of nutrition and stress resistance. Despite the lack of host range specificity of the interaction, functional diversity between AM fungal species exists. The interaction is finely regulated according to plant and fungal characters, and plant hormones are believed to orchestrate the modifications in the host plant. Using tomato as a model, an integrative analysis of the host response to different mycorrhizal fungi was performed combining multiple hormone determination and transcriptional profiling. Analysis of ethylene-, abscisic acid-, salicylic acid-, and jasmonate-related compounds evidenced common and divergent responses of tomato roots to Glomus mosseae and Glomus intraradices, two fungi differing in their colonization abilities and impact on the host. Both hormonal and transcriptional analyses revealed, among others, regulation of the oxylipin pathway during the AM symbiosis and point to a key regulatory role for jasmonates. In addition, the results suggest that specific responses to particular fungi underlie the differential impact of individual AM fungi on plant physiology, and particularly on its ability to cope with biotic stresses

Ascorbate oxidase is the potential conductor of a symphony of signaling pathways

The functional role of ascorbate oxidase (AO; EC 1.10.3.3) has never been fully explained so far, due to the difficulties in understanding the presence of an enzyme specifically oxidizing ascorbate with no obvious advantage, and the apparent disadvantage of lowering plant stress resistance as a consequence of ascorbate consumption. Here we suggest a complete change of perspective, by proposing an essential role of AO as a modulator of both ascorbate and oxygen content, with relevant implications related to signaling. By affecting the overall redox state, AO is actually involved in redox regulation in the extracellular matrix. In addition, AO can contribute to creating a hypoxic microenvironment, especially relevant in the maintenance of meristem identity and the establishment of mutualistic plant-microbe interactions. We also hypothesize the possible involvement of AO in the activation of a signaling cascade analogous to the mechanism of prolyl hydroxylases/Hypoxia Inducible Factors in animal

MSKOMP - MoSi_2-Komposite fuer Hochtemperaturanwendungen in korrosiven und oxidativen Atmosphaeren Abschlussbericht

Composite materials consisting of a matrix of MoSi_2 having a melting point above 2000 C and ceramic inclusions provide high a potential for high temperature application. Due to the formation of a thin, self healing SiO_2 film this material class is of particular interest for high temperature application in corrosive and oxidative atmospheres. The production was to be established by a reaction powder technological process with subsequent sintering with and without pressure. The samples obtained were to be tested in oxidizing atmosphere at high temperatures. During the project the economically feasible production of composites with a matrix of MoSi_2 via a reaction powder technological process could be demonstrated. An optimization in terms of purity which is a premise for high temperature application, is obligatory. (orig.)Kompositwerkstoffe mit einer Matrix aus MoSi_2 mit einem Schmelzpunkt ueber 2000 C und keramischen Einlagerungen bieten ein grosses Potenzial fuer den Einsatz bei hohen Temperaturen. Aufgrund der Ausbildung duenner, selbstheilender Deckschichten aus SiO_2 ist diese Werkstoffklasse insbesondere fuer den Hochtemperatureinsatz in korrosiven und oxidativen Atmosphaeren interessant. Die Herstellung sollte durch einen reaktionspulvertechnologischen Prozess mit anschliessender Sinterung mit und ohne Anwendung von Druck erfolgen. Die gewonnenen Proben sollten in oxidativer Atmosphaere bei hohen Temperaturen getestet werden. Im Rahmen des Projekts konnte gezeigt werden, dass die Herstellung von Kompositen mit MoSi_2-Matrix ueber einen reaktionspulvertechnologischen Prozess wirtschaftlich anwendbar ist. Hier bedarf es hinsichtlich der fuer die Verwendung bei hoher Temperatur notwendigen Reinheit noch einer Optimierung. (orig.)SIGLEAvailable from TIB Hannover: F03B492 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman