Higher plant diversity promotes higher diversity of fungal pathogens, while it decreases pathogen infection per plant

Fungal plant pathogens are common in natural communities where they affect plant physiology, plant survival, and biomass production. Conversely, pathogen transmission and infection may be regulated by plant community characteristics such as plant species diversity and functional composition that favor pathogen diversity through increases in host diversity while simultaneously reducing pathogen infection via increased variability in host density and spatial heterogeneity. Therefore, a comprehensive understanding of multi-host multi-pathogen interactions is of high significance in the context of biodiversity-ecosystem functioning. We investigated the relationship between plant diversity and aboveground obligate parasitic fungal pathogen (''pathogens'' hereafter) diversity and infection in grasslands of a long-term, large-scale, biodiversity experiment with varying plant species (1-60 species) and plant functional group diversity (1-4 groups). To estimate pathogen infection of the plant communities, we visually assessed pathogen-group presence (i.e., rusts, powdery mildews, downy mildews, smuts, and leaf-spot diseases) and overall infection levels (combining incidence and severity of each pathogen group) in 82 experimental plots on all aboveground organs of all plant species per plot during four surveys in 2006. Pathogen diversity, assessed as the cumulative number of pathogen groups on all plant species per plot, increased log-linearly with plant species diversity. However, pathogen incidence and severity, and hence overall infection, decreased with increasing plant species diversity. In addition, co-infection of plant individuals by two or more pathogen groups was less likely with increasing plant community diversity. We conclude that plant community diversity promotes pathogen-community diversity while at the same time reducing pathogen infection levels of plant individuals.

Hepatic fungal infection in a young beagle with unrecognised hereditary cobalamin deficiency (Imerslund-Gräsbeck syndrome)

A 12-month-old beagle presented for anorexia, pyrexia and vomiting. The dog had been treated intermittently with antibiotics and corticosteroids for inappetence and lethargy since five months of age. Previous laboratory abnormalities included macrocytosis and neutropenia. At presentation, the dog was lethargic, febrile and thin. Laboratory examination findings included anaemia, a left shift, thrombocytopenia, hypoglycaemia and hyperbilirubinaemia. Multiple, small, hypoechoic, round hepatic lesions were observed on abdominal ultrasound. Cytological examination of hepatic fine needle aspirates revealed a fungal infection and associated pyogranulomatous inflammation. The dog's general condition deteriorated despite supportive measures and treatment with fluconazole, and owners opted for euthanasia before hypocobalaminaemia was identified. Subsequent genomic analysis revealed a CUBN:c.786delC mutation in a homozygous state, confirming hereditary cobalamin malabsorption (Imerslund-Gräsbeck syndrome). Similar to human infants, dogs with Imerslund-Gräsbeck syndrome may rarely be presented for infectious diseases, distracting focus from the underlying primary disorder.

Sulfate and Nitrate Assimilation in Leaves of Quercus ilex and Quercus pubescens Grown Near Natural CO2 Springs in Central Italy

The effect of long-term exposure to elevated pCO2 concentrations on sulfate and nitrate assimilation was studied under field conditions using leaves from Quercus ilex and Quercus pubescens trees growing with ambient or elevated CO2 concentrations in the vicinity of three natural CO2 springs, Bossoleto, Laiatico and Sulfatara, in Tuscany, Italy. The activity of the key enzymes of sulfate assimilation, adenosine 5′-phosphosulfate reductase (APR) and nitrate assimilation, nitrate reductase (NR), were measured together with the levels of acid soluble thiols, and soluble non-proteinogenic nitrogen compounds. Whereas NR activity remained unaffected in Q. ilex or increased Q. pubescence, APR activity decreased in the area of CO2 springs. The latter changes were often accompanied by increased GSH concentrations, apparently synthesized from H2S and SO2 present in the gas mixture emitted from the CO2 springs. Thus, the diminished APR activity in leaves of Q. ilex and Q. pubescence from spring areas can best be explained by the exposure to gaseous sulfur compounds. Although the concentrations of H2S and SO2 in the gas mixture emitted from the vents at the CO2 springs were low at the Bossoleto and Laiatico spring, these sulfur gases pose physiological effects, which may override consequences of elevated pCO2.

Immune-Deficient Drosophila melanogaster: A Model for the Innate Immune Response to Human Fungal Pathogens

We explored the host-pathogen interactions of the human opportunistic fungus Candida albicans using Drosophila melanogaster. We established that a Drosophila strain devoid of functional Toll receptor is highly susceptible to the human pathogen C. albicans. Using this sensitive strain, we have been able to show that a set of specific C. albicans mutants of different virulence in mammalian infection models are also impaired in virulence in Drosophila and remarkably display the same rank order of virulence. This immunodeficient insect model also revealed virulence properties undetected in an immunocompetent murine model of infection. The genetic systems available in both host and pathogen will enable the identification of host-specific components and C. albicans genes involved in the host-fungal interplay.

Burden of serious fungal infections in Tanzania.

The incidence and prevalence of fungal infections in Tanzania remains unknown. We assessed the annual burden in the general population and among populations at risk. Data were extracted from 2012 reports of the Tanzanian AIDS program, WHO, reports, Tanzanian census, and from a comprehensive PubMed search. We used modelling and HIV data to estimate the burdens of Pneumocystis jirovecii pneumonia (PCP), cryptococcal meningitis (CM) and candidiasis. Asthma, chronic obstructive pulmonary disease and tuberculosis data were used to estimate the burden of allergic bronchopulmonary aspergillosis (ABPA) and chronic pulmonary aspergillosis (CPA). Burdens of candidaemia and Candida peritonitis were derived from critical care and/or cancer patients' data. In 2012, Tanzania's population was 43.6 million (mainland) with 1 500 000 people reported to be HIV-infected. Estimated burden of fungal infections was: 4412 CM, 9600 PCP, 81 051 and 88 509 oral and oesophageal candidiasis cases respectively. There were 10 437 estimated posttuberculosis CPA cases, whereas candidaemia and Candida peritonitis cases were 2181 and 327 respectively. No reliable data exist on blastomycosis, mucormycosis or fungal keratitis. Over 3% of Tanzanians suffer from serious fungal infections annually, mostly related to HIV. Cryptococcosis and PCP are major causes of mycoses-related deaths. National surveillance of fungal infections is urgently needed.

Inhibition of photosynthesis by high temperature in oak (Quercus pubescens L.) leaves grown under natural conditions closely correlates with a reversible heat-dependent reduction of the activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase

Inhibition of the net photosynthetic CO2 assimilation rate (Pn) by high temperature was examined in oak (Quercus pubescens L.) leaves grown under natural conditions. Combined measurements of gas exchange and chlorophyll (Chl) a fluorescence were employed to differentiate between inhibition originating from heat effects on components of the thylakoid membranes and that resulting from effects on photosynthetic carbon metabolism. Regardless of whether temperature was increased rapidly or gradually, Pn decreased with increasing leaf temperature and was more than 90% reduced at 45 °C as compared to 25 °C. Inhibition of Pn by heat stress did not result from reduced stomatal conductance (gs), as heat-induced reduction of gs was accompanied by an increase of the intercellular CO2 concentration (Ci). Chl a fluorescence measurements revealed that between 25 and 45 °C heat-dependent alterations of thylakoid-associated processes contributed only marginally, if at all, to the inhibition of Pn by heat stress, with photosystem II being remarkably well protected against thermal inactivation. The activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) decreased from about 90% at 25 °C to less than 30% at 45 °C. Heat stress did not affect Rubisco per se, since full activity could be restored by incubation with CO2 and Mg2+. Western-blot analysis of leaf extracts disclosed the presence of two Rubisco activase polypeptides, but heat stress did not alter the profile of the activase bands. Inhibition of Pn at high leaf temperature could be markedly reduced by artificially increasing Ci. A high Ci also stimulated photosynthetic electron transport and resulted in reduced non-photochemical fluorescence quenching. Recovery experiments showed that heat-dependent inhibition of Pn was largely, if not fully, reversible. The present results demonstrate that in Q. pubescens leaves the thylakoid membranes in general and photosynthetic electron transport in particular were well protected against heat-induced perturbations and that inhibition of Pn by high temperature closely correlated with a reversible heat-dependent reduction of the Rubisco activation state.

Layer-by-layer grown scalable redox-active ruthenium-based molecular multilayer thin films for electrochemical applications and beyond

Here we report the first study on the electrochemical energy storage application of a surface-immobilized ruthenium complex multilayer thin film with anion storage capability. We employed a novel dinuclear ruthenium complex with tetrapodal anchoring groups to build well-ordered redox-active multilayer coatings on an indium tin oxide (ITO) surface using a layer-by-layer self-assembly process. Cyclic voltammetry (CV), UV-Visible (UV-Vis) and Raman spectroscopy showed a linear increase of peak current, absorbance and Raman intensities, respectively with the number of layers. These results indicate the formation of well-ordered multilayers of the ruthenium complex on ITO, which is further supported by the X-ray photoelectron spectroscopy analysis. The thickness of the layers can be controlled with nanometer precision. In particular, the thickest layer studied (65 molecular layers and approx. 120 nm thick) demonstrated fast electrochemical oxidation/reduction, indicating a very low attenuation of the charge transfer within the multilayer. In situ-UV-Vis and resonance Raman spectroscopy results demonstrated the reversible electrochromic/redox behavior of the ruthenium complex multilayered films on ITO with respect to the electrode potential, which is an ideal prerequisite for e.g. smart electrochemical energy storage applications. Galvanostatic charge–discharge experiments demonstrated a pseudocapacitor behavior of the multilayer film with a good specific capacitance of 92.2 F g−1 at a current density of 10 μA cm−2 and an excellent cycling stability. As demonstrated in our prototypical experiments, the fine control of physicochemical properties at nanometer scale, relatively good stability of layers under ambient conditions makes the multilayer coatings of this type an excellent material for e.g. electrochemical energy storage, as interlayers in inverted bulk heterojunction solar cell applications and as functional components in molecular electronics applications.

Association of lectin pathway proteins with intra-abdominal Candida infection in high-risk surgical intensive-care unit patients. A prospective cohort study within the fungal infection network of Switzerland

OBJECTIVES Human studies on the role of mannose-binding lectin (MBL) in patients with invasive candidiasis have yielded conflicting results. We investigated the influence of MBL and other lectin pathway proteins on Candida colonization and intra-abdominal candidiasis (IAC) in a cohort of high-risk patients. METHODS Prospective observational cohort study of 89 high-risk intensive-care unit (ICU) patients. Levels of lectin pathway proteins at study entry and six MBL2 single-nucleotide polymorphisms were analyzed by sandwich-type immunoassays and genotyping, respectively, and correlated with development of heavy Candida colonization (corrected colonization index (CCI) ≥0.4) and occurrence of IAC during a 4-week period. RESULTS Within 4 weeks after inclusion a CCI ≥0.4 and IAC was observed in 47% and 38% of patients respectively. Neither serum levels of MBL, ficolin-1, -2, -3, MASP-2 or collectin liver 1 nor MBL2 genotypes were associated with a CCI ≥0.4. Similarly, none of the analyzed proteins was found to be associated with IAC with the exception of lower MBL levels (HR 0.74, p = 0.02) at study entry. However, there was no association of MBL deficiency (<0.5 μg/ml), MBL2 haplo- or genotypes with IAC. CONCLUSION Lectin pathway protein levels and MBL2 genotype investigated in this study were not associated with heavy Candida colonization or IAC in a cohort of high-risk ICU patients.

Light intensity selectively influences the distribution and further redistribution of macro- and micronutrients in hydroponically grown wheat ( Triticum aestivum L.)

Investigations were focused on light effects on allocation of root-borne macronutrients (calcium, magnesium and potassium) and micronutrients (iron, manganese, zinc and copper) in roots, shoots and harvested grains of wheat (Triticum aestivum L.). Plants were exposed to low (100 μmol photons m−2 s−1) or high light (380 μmol photons m−2 s−1). High light stimulated both root and shoot growth. While the total contents per plant of some nutrients were markedly higher (calcium and potassium) or lower (copper) under high light, no major differences were observed for other nutrients. The distribution of nutrients and the further redistribution within the shoot were influenced by the light intensity in an element-specific manner. Nutrients were selectively directed to the leaves of the main shoot (low light) or to the tillers (high light). The quality of the harvested grains was also affected by the light intensity.

Foliar fungal pathogens and grassland biodiversity

By attacking plants, herbivorous mammals, insects, and belowground pathogens are known to play an important role in maintaining biodiversity in grasslands. Foliar fungal pathogens are ubiquitous in grassland ecosystems, but little is known about their role as drivers of community composition and diversity. Here we excluded foliar fungal pathogens from perennial grassland by using fungicide to determine the effect of natural levels of disease on an otherwise undisturbed plant community. Importantly, we excluded foliar fungal pathogens along with rabbits, insects, and mollusks in a full factorial design, which allowed a comparison of pathogen effects along with those of better studied plant enemies. This revealed that fungal pathogens substantially reduced aboveground plant biomass and promoted plant diversity and that this especially benefited legumes. The scale of pathogen effects on productivity and biodiversity was similar to that of rabbits and insects, but different plant species responded to the exclusion of the three plant enemies. These results suggest that theories of plant coexistence and management of biodiversity in grasslands should consider foliar fungal pathogens as potentially important drivers of community composition.

A fungal endophyte helps plants to tolerate root herbivory through changes in gibberellin and jasmonate signaling

Plant–microbe mutualisms can improve plant defense, but the impact of root endophytes on below-ground herbivore interactions remains unknown. We investigated the effects of the root endophyte Piriformospora indica on interactions between rice (Oryza sativa) plants and its root herbivore rice water weevil (RWW; Lissorhoptrus oryzophilus), and how plant jasmonic acid (JA) and GA regulate this tripartite interaction. Glasshouse experiments with wild-type rice and coi1-18 and Eui1-OX mutants combined with nutrient, jasmonate and gene expression analyses were used to test: whether RWW adult herbivory above ground influences subsequent damage caused by larval herbivory below ground; whether P. indica protects plants against RWW; and whether GA and JA signaling mediate these interactions. The endophyte induced plant tolerance to root herbivory. RWW adults and larvae acted synergistically via JA signaling to reduce root growth, while endophyte-elicited GA biosynthesis suppressed the herbivore-induced JA in roots and recovered plant growth. Our study shows for the first time the impact of a root endophyte on plant defense against below-ground herbivores, adds to growing evidence that induced tolerance may be an important root defense, and implicates GA as a signal component of inducible plant tolerance against biotic stress.

Solute losses from various shoot parts of field-grown wheat by leakage in the rain

Leakage from field-grown wheat was investigated during two seasons differing considerably in their rainfall patterns. For all solutes analyzed, these losses were low from non-senescing plant parts, increased after the onset of senescence and became maximal in fully senesced (dry, brown) organs. The cumulative losses of potassium by leakage in the rain were 65% of the content at anthesis for the flag leaf and 95% for the third leaf from the top, while these relative values were lower for magnesium (50 to 80%) and calcium (around 55%) and extremely low for sodium (<10%). The differences between potassium and sodium may be due to a different compartmentation on the tissue level or on the subcellular level. It became evident that for certain nutrients (e.g. potassium or magnesium) leakage in the rain may represent a major loss from senescing leaves and can be a relevant flux in maturing wheat.