1,721,151 research outputs found
Copper deficiency or toxicity in ectomycorrhizal pines?
No full textfeatures but not others, and host specificity was less important than assumed, with evidence for host-shifts during the evolution of the genus (pp. 41-56). The recognition of a new lignicolous species of Marchandio-myces, a genus hitherto only including lichenicolous species, also provides evidence of substrate switches as it is closest to the lichenicolous M. corallinus but has M. aurantiacus (which is also lichenicolous) as the sister group ; it is suggested that in this case the lichenicolous habit arose secondarily on two separate occasions from an ancestral lignicolous one (pp. 57-70). The edible Pleurotus eryngii varies considerably morphologically and several varieties have been distinguished. A comparative study of 154 strains using RAPDs and minisatellites showed correlations with fruit body numbers and weights, but not with geographical locations nor taxonomic groupings ; a high level of heterogeneity exisited within populations (pp. 71-80). In contrast, variability in the charcoal root rot pathogen, Macrophomina phaseolina, examined by SSR and microsatellite markers, revealed three major groups correlated with hosts (soybean vs cotton) and geographical origins (pp. 81-86). In order to further advance precise identifications of Alternaria species, restriction maps of the IGS region of nrDNA were constructed for 15 species and revealed both conserved and and variable domains, the latter showing considerable differences amongst the taxa (pp. 87-95). Two specific primers have been designed and tested for the detection of Sclerotinia pseudotuberosa, causal agent of black rot of Castanea sativa fruits, and were capable of detecting the fungus when growing en-dophytically and in picogram quantities (pp. 96-102). The effect of the biocontrol fungus Phlebiopsis gigantea on Heterobasdion colonization on conifer stump, has been examined by denaturing gradient gel electro-phoresis of SSU rDNA fragments obtained directly by PCR from the wood ; the treatment did not appear to reduce overall fungal diversity, and the method is a promising one for the analysis of fungal communities on stumps (pp. 103-114). Using lignin peroxidase and laccase gene-specific PCR primers, laccase genes proved widespread amongst the basidiomycetes tested and were also discovered for the first time in Xylariaceae, although in that case the enzymes were not produced in vitro as they were in the basidiomycetes (pp. 115-124)
Gene expression studies in different genotypes of an ectomycorrhizal fungus require a high number of reliable reference genes
No full textQuantitative reverse transcription PCR (qRT-PCR) has become the standard technique for the expression analysis of a set of chosen genes of interest. The accuracy and reliability of qRT-PCR measurements strongly depends on the normalization with appropriate endogenous reference genes. In this study a set of candidate reference genes for the use in gene expression studies of a basidiomycete fungus, Suillus luteus, exposed to toxic concentrations of zinc or cadmium was identified, evaluated and validated. Seven candidate genes were selected from cDNA-AFLP as stably expressed and the algorithms geNorm and Normfinder were used to evaluate these genes alongside the traditionally used housekeeping genes (actin, tubulin) in different S. luteus isolates. The use of several S. luteus isolates revealed that each isolate has its own most stably expressed set of reference genes, regardless of the metal treatments, in casu metal exposures. Metal treatments had only a minor impact on the expression of the candidate reference genes. The validated reference genes outperform the in fungal research commonly used single, arbitrary chosen (“housekeeping”) genes in terms of reliability, and have the potential to be suitable reference genes when studying the effect of other environmental factors. A relatively high number of reference genes is required to correct for intraspecific variability when studying natural populations.</jats:p
An ectomycorrhizal symbiosis differently affects host susceptibility to two congeneric fungal pathogens
Full text linkThe role of ectomycorrhizal fungi in modulating host susceptibility to fungal pathogens is poorly known. Pinus sylvestris susceptibility to two congeneric fungal pathogens was compared between mycorrhizal and non-mycorrhizal plants. The ectomycorrhizal fungus was Suillus luteus, while the pathogens were Heterobasidion irregulare and H. annosum. H. irregulare is native to North-America and invasive to Europe, whereas S. luteus and H. annosum are native to Eurasia. Non-mycorrhizal plants were equally susceptible to both pathogens. Mycorrhizal plants were significantly less susceptible to H. annosum than non-mycorrhizal plants, whereas there were no differences when considering H. irregulare. The abundance of ectomycorrhizas was negatively and significantly correlated to the level of host susceptibility only to H. annosum. This study shows that the protective role of ectomycorrhizal fungi may differ when the host is challenged by congeneric fungal pathogens. Results add a further clue to explain and predict the invasiveness of H. irregulare in Europe. (C) 2018 Elsevier Ltd and British Mycological Society. All rights reserved.This work was supported by the Italian Ministry of Education, University and Research, within the FIRB program (grant number RBFR1280NN). Authors are grateful to Francois Rineau for assistance with mycorrhiza inoculations and to Matteo Garbelotto for helpful comments on the manuscript and for revising the English. The authors wish to thank the Editor and the anonymous Reviewers for insightful suggestions on how to improve the manuscript
Identification of genes differentially expressed during the interaction between the plant symbiont Suillus luteus and two plant pathogenic allopatric Heterobasidion species
No full textThe effects of biological invasions by non-native species have been widely studied in terms of environmental, economic, and human health impacts. However, little is known about the consequences that non-native plant pathogens may determine on host plant symbionts, such as ectomycorrhizal (ECM) fungi. In this study, interactions between Suillus luteus, an ECM fungus of pine trees, and the allopatrically differentiated fungal pathogens of pines Heterobasidion irregulare and H. annosum were investigated in dual culture by morphological and gene expression analyses. Growth of S. luteus was inhibited by both Heterobasidion species, but based on statistical analysis, growth inhibition was due to the isolate rather than to the species. The expression analysis on genes related to cell wall hydrolytic enzymes and hydrophobins, putatively involved in the fungus-fungus interaction, allowed to identify significantly up- and down-regulated genes both in the symbiont and in the pathogens. Based on the transcript analysis, it was not possible to distinguish the impact of the two pathogenic species on the ECM fungus. The only exception was a S. luteus gene coding for a putative chitinase (SlGH18_8356) that was found to be differentially regulated during interaction with H. irregulare compared to H. annosum.This work was supported by the Italian Ministry of Education, University and Research, within the FIRB program (grant number RBFRI280NN)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Fungal heavy metal adaptation through single nucleotide polymorphisms and copy‐number variation
No full textHuman-altered environments can shape the evolution of organisms. Fungi are no exception, although little is known about how they withstand anthropogenic pollution. Here, we document adaptation in the mycorrhizal fungusSuillus luteusdriven by soil heavy metal contamination. Genome scans across individuals from recently polluted and nearby unpolluted soils in Belgium revealed low divergence across isolates and no evidence of population structure based on soil type. However, we detected single nucleotide polymorphism divergence and gene copy-number variation, with different genetic combinations potentially conferring the ability to persist in contaminated soils. Variants were shared across the population but found to be under selection in isolates exposed to pollution and located across the genome, including in genes involved in metal exclusion, storage, immobilization and reactive oxygen species detoxification. Together, our results point toS. luteusundergoing the initial steps of adaptive divergence and contribute to understanding the processes underlying local adaptation under strong environmental selection.Joint Genome Institute Community Science Program, Grant/Award Number: 502931; NSF, Grant/Award Number: DEB-1554181; Flanders Innovation & Entrepreneurships PhD fellowship, Grant/Award Number: 141461; Hawaii's Agricultural Experiment Station; Montana's Agricultural Experiment Station; Fonds Wetenschappelijk Onderzoek, Grant/Award Number: G079213NBranco, S (corresponding author), Univ Colorado Denver, Dept Integrat Biol, Denver, CO 80202 USA.
Bazzicalupo, AL (corresponding author), Univ British Columbia, Dept Zool, Vancouver, BC, Canada.
[email protected]; [email protected]
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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