The mutualistic fungus Piriformospora indica protects barley roots from a loss of antioxidant capacity caused by the necrotrophic pathogen Fusarium culmorum

Fusarium culmorum causes root rot in barley (Hordeum vulgare), resulting in severely reduced plant growth and yield. Pretreatment of roots with chlamydospores of the mutualistic root-colonizing basidiomycete Piriformospora indica (Agaricomycotina) prevented necrotization of root tissues and plant growth retardation commonly associated with Fusarium root rot. Quantification of Fusarium infections with a real-time PCR assay revealed a correlation between root rot symptoms and the relative amount of fungal DNA. Fusarium-infected roots showed reduced levels of ascorbate and glutathione (GSH), along with reduced activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR). Consistent with this, Fusarium-infected roots showed elevated levels of lipid hydroperoxides and decreased ratios of reduced to oxidized forms of ascorbate and glutathione. In clear contrast, roots treated with P. indica prior to inoculation with F. culmorum showed levels of ascorbate and GSH that were similar to controls. Likewise, lipid peroxidation and the overall reduction in antioxidant enzyme activities were largely attenuated by P. indica in roots challenged by F. culmorum. These results suggest that P. indica protects roots from necrotrophic pathogens at least partly, through activating the plant’s antioxidant capacity

Fabrication of Pt/Ru Nanoparticle Pair Arrays with Controlled Separation and their Electrocatalytic Properties

Aiming at the investigation of spillover and transport effects in electrocatalytic reactions on bimetallic catalyst electrodes, we have prepared novel, nanostructured electrodes consisting of arrays of homogeneously distributed pairs of Pt and Ru nanodisks of uniform size and with controlled separation on planar glassy carbon substrates. The nanodisk arrays (disk diameter approximate to 60 nm) were fabricated by hole-mask colloidal lithography; the separation between pairs of Pt and Ru disks was varied from -25 nm (overlapping) via +25 nm to +50 nm. Morphology and (surface) composition of the Pt/Ru nanodisk arrays Were characterized by scanning electron microscopy, energy dispersive X-ray analysis, and X-ray Photoelectron spectroscopy, the electrochemical/electrocatalytic properties were explored by cyclic voltammetry, COad monolayer oxidation ("COad stripping"), and potentiodynamic hydrogen oxidation. Detailed analysis of the 2 COad oxidation peaks revealed that on all bimetallic pairs these cannot be reproduced by superposition of the peaks obtained on electrodes with Pt/Pt or Ru/Ru pairs, pointing to effective Pt-Ru interactions even between rather distant pairs (50 nm). Possible reasons for this observation and its relevance for the understanding of previous reports of highly active catalysts with separate Pt and Ru nanoparticles are discussed. The results clearly demonstrate that this preparation method is perfectly suited for fabrication of planar model electrodes with well-defined arrays of bimetallic nanodisk pairs, which opens up new possibilities for model studies of electrochemical/electrocatalytic reactions

Detection of CO desorbing from the Ni electrode surface by DEMS

Electrochemical research on metal-CO interactions is generally related to the role of CO as a poison in the electro-oxidation reactions of organic fuels at noble metal electrodes. A small number of studies have treated the interaction of a nickel electrode with CO, either as a complement to studies of CO2 electroreduction, in which case CO is considered as an intermediate, or in comrection with an interest in Ni as a potential low cost electrocatalyst. In addition, the study of adsorption and desorption reactions on nickel electrodes is also important for understanding the action of inhibitors. The adsorption of CO was also used to protect a Ni(ll1) surface during the transfer from UHV into alkaline electrolytes.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

WRKY6 restricts Piriformospora indica-stimulated and phosphate-induced root development in Arabidopsis

BACKGROUND: Arabidopsis root growth is stimulated by Piriformospora indica, phosphate limitation and inactivation of the WRKY6 transcription factor. Combinations of these factors induce unexpected alterations in root and shoot growth, root architecture and root gene expression profiles. RESULTS: The results demonstrate that P. indica promotes phosphate uptake and root development under Pi limitation in wrky6 mutant. This is associated with the stimulation of PHOSPHATE1 expression and ethylene production. Expression profiles from the roots of wrky6 seedlings identified genes involved in hormone metabolism, transport, meristem, cell and plastid proliferation, and growth regulation. 25 miRNAs were also up-regulated in these roots. We generated and discuss here a list of common genes which are regulated in growing roots and which are common to all three growth stimuli investigated in this study. CONCLUSION: Since root development of wrky6 plants exposed to P. indica under phosphate limitation is strongly promoted, we propose that common genes which respond to all three growth stimuli are central for the control of root growth and architecture. They can be tested for optimizing root growth in model and agricultural plants. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12870-015-0673-4) contains supplementary material, which is available to authorized users

The beneficial fungus Piriformospora indica protects Arabidopsis from Verticillium dahliaeinfection by downregulation plant defense responses

BACKGROUND: Verticillium dahliae (Vd) is a soil-borne vascular pathogen which causes severe wilt symptoms in a wide range of plants. The microsclerotia produced by the pathogen survive in soil for more than 15 years. RESULTS: Here we demonstrate that an exudate preparation induces cytoplasmic calcium elevation in Arabidopsis roots, and the disease development requires the ethylene-activated transcription factor EIN3. Furthermore, the beneficial endophytic fungus Piriformospora indica (Pi) significantly reduced Vd-mediated disease development in Arabidopsis. Pi inhibited the growth of Vd in a dual culture on PDA agar plates and pretreatment of Arabidopsis roots with Pi protected plants from Vd infection. The Pi-pretreated plants grew better after Vd infection and the production of Vd microsclerotia was dramatically reduced, all without activating stress hormones and defense genes in the host. CONCLUSIONS: We conclude that Pi is an efficient biocontrol agent that protects Arabidopsis from Vd infection. Our data demonstrate that Vd growth is restricted in the presence of Pi and the additional signals from Pi must participate in the regulation of the immune response against Vd. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12870-014-0268-5) contains supplementary material, which is available to authorized users