BibSonomy publications for /user/ipazphytoFri Jul 25 10:21:37 CEST 2008JOURNAL OF PLANT PHYSIOLOGY160-70Systemic and local modulation of plant responses by Piriformospora indica and related Sebacinales species1652008induced_resistance endophyte mutualism compatibility powdery_mildew IFZ root Piriformospora indica is a fungus of the order Sebacinales (Basidiomycota) infesting roots of mono- and dicotyledonous plants. Endophytic fungal colonization leads to enhanced plant growth while host cell. death is required for proliferation in differentiated root tissue to form a mutualistic interaction. Colonization of barley roots by P. indica and related Sebacina vermifera strains also leads to systemic resistance against the leaf pathogenic fungus Blumerio graminis f.sp. hordei due to a yet unknown mechanism of induced resistance. In order to elucidate plant response pathways governed by these root endophytes, we analyzed gene expression in barley plants exhibiting an established symbiosis with P. indica 3 weeks after inoculation. P. indica-cotonized roots showed no induction of defence-related genes, white other genes showed a differential regulation pattern indicating a faster P. indica-dependent root development. Gene expression analysis of leaves detected only few systemically induced mRNAs. Among differentially regulated transcripts, we characterized the pathogenesis-related gene HvPr17b and the molecular chaperone HvHsp70 in more detail. HvPr17b shows similarity with TaWC15, a wheat gene inducible by chemical resistance inducers and salicylate, and was previously proven to exhibit antifungal activity against B. graminis. HvHsp70 is the first gene found to systemically indicate root colonization with endophytic fungi of the order Sebocinales. Both genes are discussed as markers for endophytic colonization and resulting systemic responses. (C) 2007 Elsevier GmbH. All rights reserved.Wed May 14 10:24:29 CEST 2008JOURNAL OF PLANT PHYSIOLOGY11-4Compatible host-microbe interactions: Mechanistic studies enabling future agronomical solutions1652008imported IFZ Wed May 14 10:24:29 CEST 2008NEW PHYTOLOGIST3634-646Nitric oxide generation in Vicia faba phloem cells reveals them to be sensitive detectors as well as possible systemic transducers of stress signals1782008phloem IFZ stress salicylic_acid nitric_oxide_(NO) systemic_signalling nitric_oxide_synthase hydrogen_peroxide_(H2O2) pathogen_resistance Vascular tissue was recently shown to be capable of producing nitric oxide (NO), but the production sites and sources were not precisely determined. Here, NO synthesis was analysed in the phloem of Vicia faba in response to stress- and pathogen defence-related compounds. The chemical stimuli were added to shallow paradermal cortical cuts in the main veins of leaves attached to intact plants. NO production in the bare-lying phloem area was visualized by real-time confocal laser scanning microscopy using the NO-specific fluorochrome 4,5-diaminofluorescein diacetate (DAF-2 DA). Abundant NO generation in companion cells was induced by 500 mu M salicylic acid (SA) and 10 mu M hydrogen peroxide (H2O2), but the fungal elicitor chitooctaose was much less effective. Phloem NO production was found to be dependent on Ca2+ and mitochondrial electron transport and pharmacological approaches found evidence for activity of a plant NO synthase but not a nitrate reductase. DAF fluorescence increased most strongly in companion cells and was occasionally observed in phloem parenchyma cells. Significantly, accumulation of NO in sieve elements could be demonstrated. These findings suggest that the phloem perceives and produces stress-related signals and that one mechanism of distal signalling involves the production and transport of NO in the phloem.Wed May 14 10:24:29 CEST 2008JOURNAL OF PLANT PHYSIOLOGY152-59Interactive signal transfer between host and pathogen during successful infection of barley leaves by Blumeria graminis and Bipolaris sorokiniana1652008surface_pH apoplastic_pH resistance barley IFZ compatibility Using ion-selective microprobes, interactive signalling between barley and Blumeria graminis or Bipolaris sorokiniana has been investigated. The question was raised whether a biotrophically growing fungus manipulates the electrical driving forces (membrane potential., transmembrane pH), required for H+ cotransport of energy-rich compounds. Electrodes were positioned in the substomatal cavity of open stomata or on the leaf surface, and pH was measured continuously up to several days during fungal development. We demonstrate that surface and apoplastic fluids are electrically coupled and respond in a similar manner to stimuli. Apoplastic pH, monitored from the moment of inoculation with conidia, reveals several phases: 2-4 h after inoculation of the barley leaf with either fungus, the host displays rapid transient responses after its first contact with the fungal cell wall; apoplastic pH and pCa increases, cytoplasmic pH and pCa decreases. About 1 day after inoculation, the apoplastic pH increases by up to 2 pH units, which is thought to reflect a resistance response against the intruder. Whereas barley leaf cells possess a membrane potential of -152 +/- 5 mV, hyphae of B. graminis yield -251 +/- 8 mV, indicative of a substantial driving force advantage for the fungus. Although the resting membrane potential of barley remains constant during the first days after inoculation, leaves infected with B. sorokiniona get confronted with an energy problem, indicated by a retarded repolarization following a ��light-off" stimulus. Five daysWed May 14 10:24:29 CEST 2008FEMS MICROBIOLOGY LETTERS11-7Root cell death and systemic effects of Piriformospora indica: a study on mutualism2752007IFZ growth_promotion arbuscular_mycorrhizal mutualism Sebacinales resistance_induction programmed_cell_death fungi The root systems of most terrestrial plants are confronted with a huge variety of invasive microorganisms that either can cause detrimental effects or in case of mutualistic symbiosis provide benefits for the host. In either case, establishment of the parasitic or mutualistic interaction is the result of a highly sophisticated cross-talk between the partners. Despite the ecological importance of mutualistic symbioses, the molecular events accompanied by this phenomenon are far from being understood. Piriformospora indica represents a recently discovered fungus that transfers considerable beneficial impact to its host plants. In this review, the current knowledge on this novel symbiosis is summarized by focusing on its biological effects in hosts and the role of programmed cell death in the establishment of the mutualistic interaction.Wed May 14 10:24:29 CEST 2008JOURNAL OF PLANT DISEASES AND PROTECTION6263-268Piriformospora indica protects barley from root rot caused by Fusarium graminearum1142007bio-control IFZ pathogen PR_genes root_endophyte Q-PCR_quantification The beneficial endophytic fungus Piriformospora indica colonizes barley (Hordeum vulgare L.) roots, which results in protection against diseases and abiotic stress and eventually in higher yield. Infection of the roots with pathogenic necrotrophic fungi of the genus Fusarium, in contrast, leads to necrotized roots and severe reduction of root and shoot biomass. Upon infestation with P. indica, roots were protected from Fusarium infections as evidenced by reduced root rot symptoms. Consistently, Fusarium quantification using quantitative polymerase chain reaction (Q-PCR) revealed a correlation between reduced root rot symptoms and the relative amount of fungal DNA. In vitro analysis of the interaction of P. indica and F. graminearum under axenic culture conditions did not reveal reciprocal growth inhibition suggesting that retardation of Fusarium in roots is mediated by a plant response rather than by antibiosis. Expression of pathogenesis-related genes strongly increased in response to F. graminearum infections, but in contrast was diminished in the presence of P. indica, indicating that PR proteins do not play a crucial role in the P. indica-mediated resistance response to Fusarium.