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      Discovery of a new species of the Hypoxylon rubiginosum complex from Iran and antagonistic activities of Hypoxylon spp. against the Ash Dieback pathogen, Hymenoscyphus fraxineus , in dual culture


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          During a survey of xylarialean fungi in Northern Iran, several specimens that showed affinities to the Hypoxylon rubiginosum complex were collected and cultured. A comparison of their morphological characters, combined with a chemotaxonomic study based on high performance liquid chromatography, coupled with diode array detection and mass spectrometry (HPLC-DAD/MS) and a multi-locus phylogeny based on ITS, LSU, rbp2 and tub2 DNA sequences, revealed a new species here described as Hypoxylon guilanense . In addition, Hypoxylon rubiginosum sensu stricto was also encountered. Concurrently, an endophytic isolate of the latter species showed strong antagonistic activities against the Ash Dieback pathogen, Hymenoscyphus fraxineus , in a dual culture assay in our laboratory. Therefore, we decided to test the new Iranian fungi for antagonistic activities against the pathogen, along with several cultures of other Hypoxylon species that are related to H. rubiginosum . Our results suggest that the antagonistic effects of Hypoxylon spp. against Hym. fraxineus are widespread and that they are due to the production of antifungal phomopsidin derivatives in the presence of the pathogen.

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          Hypoxylon pulicicidum sp. nov. (Ascomycota, Xylariales), a Pantropical Insecticide-Producing Endophyte

          Background Nodulisporic acids (NAs) are indole diterpene fungal metabolites exhibiting potent systemic efficacy against blood-feeding arthropods, e.g., bedbugs, fleas and ticks, via binding to arthropod specific glutamate-gated chloride channels. Intensive medicinal chemistry efforts employing a nodulisporic acid A template have led to the development of N-tert-butyl nodulisporamide as a product candidate for a once monthly treatment of fleas and ticks on companion animals. The source of the NAs is a monophyletic lineage of asexual endophytic fungal strains that is widely distributed in the tropics, tentatively identified as a Nodulisporium species and hypothesized to be the asexual state of a Hypoxylon species. Methods and Results Inferences from GenBank sequences indicated that multiple researchers have encountered similar Nodulisporium endophytes in tropical plants and in air samples. Ascomata-derived cultures from a wood-inhabiting fungus, from Martinique and closely resembling Hypoxylon investiens, belonged to the same monophyletic clade as the NAs-producing endophytes. The hypothesis that the Martinique Hypoxylon collections were the sexual state of the NAs-producing endophytes was tested by mass spectrometric analysis of NAs, multi-gene phylogenetic analysis, and phenotypic comparisons of the conidial states. We established that the Martinique Hypoxylon strains produced an ample spectrum of NAs and were conspecific with the pantropical Nodulisporium endophytes, yet were distinct from H. investiens. A new species, H. pulicicidum, is proposed to accommodate this widespread organism. Conclusions and Significance Knowledge of the life cycle of H. pulicicidum will facilitate an understanding of the role of insecticidal compounds produced by the fungus, the significance of its infections in living plants and how it colonizes dead wood. The case of H. pulicicidum exemplifies how life cycle studies can consolidate disparate observations of a fungal organism, whether from environmental sequences, vegetative mycelia or field specimens, resulting in holistic species concepts critical to the assessment of the dimensions of fungal diversity.
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            Diversity of biologically active secondary metabolites from endophytic and saprotrophic fungi of the ascomycete order Xylariales

            The diversity of secondary metabolites in the fungal order Xylariales is reviewed with special emphasis on correlations between chemical diversity and biodiversity as inferred from recent taxonomic and phylogenetic studies. Covering: up to December 2017 The diversity of secondary metabolites in the fungal order Xylariales is reviewed with special emphasis on correlations between chemical diversity and biodiversity as inferred from recent taxonomic and phylogenetic studies. The Xylariales are arguably among the predominant fungal endophytes, which are the producer organisms of pharmaceutical lead compounds including the antimycotic sordarins and the antiparasitic nodulisporic acids, as well as the marketed drug, emodepside. Many Xylariales are “macromycetes”, which form conspicuous fruiting bodies (stromata), and the metabolite profiles that are predominant in the stromata are often complementary to those encountered in corresponding mycelial cultures of a given species. Secondary metabolite profiles have recently been proven highly informative as additional parameters to support classical morphology and molecular phylogenetic approaches in order to reconstruct evolutionary relationships among these fungi. Even the recent taxonomic rearrangement of the Xylariales has been relying on such approaches, since certain groups of metabolites seem to have significance at the species, genus or family level, respectively, while others are only produced in certain taxa and their production is highly dependent on the culture conditions. The vast metabolic diversity that may be encountered in a single species or strain is illustrated based on examples like Daldinia eschscholtzii , Hypoxylon rickii , and Pestalotiopsis fici . In the future, it appears feasible to increase our knowledge of secondary metabolite diversity by embarking on certain genera that have so far been neglected, as well as by studying the volatile secondary metabolites more intensively. Methods of bioinformatics, phylogenomics and transcriptomics, which have been developed to study other fungi, are readily available for use in such scenarios.
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              Affinities of Phylacia and the daldinoid Xylariaceae, inferred from chemotypes of cultures and ribosomal DNA sequences.

              A chemotaxonomic evaluation using hplc profiling was undertaken to resolve the infrageneric and intergeneric affinities of over 150 strains of Xylariaceae. Daldinia placentiformis, Hypoxylon nicaraguense, H. polyporus, and Phylacia sagrana were found to contain 8-methoxy-1-naphthol, which is apparently absent in Annulohypoxylon, Hypoxylon, and related genera with bipartite stromata. D. placentiformis and other species of Daldinia and Entonaema produced this naphthol, 5-hydroxy-2-methylchromone, isosclerone derivatives, and 'AB-5046' phytotoxins. Phylacia sagrana differed from most Daldinia spp., except for D. caldariorum, by producing eutypine derivatives in addition to the above compounds. Indolylquinones were observed in H. nicaraguense and H. polyporus. Isosclerones were also identified in the A. multiforme complex, but Hypoxylon and other Annulohypoxylon and most Hypoxylon spp. studied Annulohypoxylon spp. contained 5-methylmellein as the major metabolite of their cultures. Based on the occurrence of the above metabolites, further mellein-type dihydroisocoumarins, teleomorphic and anamorphic Xylariaceae with Nodulisporium-like anamorphs ('Hypoxyloideae') were divided into various chemotypes. A comparison of their 5.8S/ITS nuc-rDNA sequences agreed in some important aspects with the above results: H. nicaraguense and H. polyporus appeared basal to a clade comprising Daldinia, Entonaema, and Ph. sagrana. The latter species appeared allied to D. caldariorum, but was distantly related to Pyrenomyxa morganii and Hypoxylon s. str.

                Author and article information

                Pensoft Publishers
                24 April 2020
                : 66
                : 105-133
                [1 ] Department of Plant Protection, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran Helmholtz-Zentrum für Infektionsforschung GmbH Braunschweig Germany
                [2 ] Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, 1030, Wien, Austria University of Guilan Rasht Islamic Republic of Iran
                [3 ] Helmholtz-Zentrum für Infektionsforschung GmbH, Dept. Microbial Drugs, Inhoffenstrasse 7, 38124, Braunschweig, Germany University of Vienna Vienna Austria
                [4 ] Institute of Forest Entomology, Forest Pathology and Forest Protection, Department of Forest and Soil Sciences, BOKU-University of Natural Resources and Life Sciences, Franz-Schwackhöfer-Haus, Peter-Jordan-Straße 82/I, 1190, Vienna, Austria BOKU-University of Natural Resources and Life Sciences Vienna Austria
                Author notes
                Corresponding author: Marc Stadler ( Marc.Stadler@ 123456helmholtz-hzi.de )

                Academic editor: T. Lumbsch

                Mohammad Javad Pormoghadam, Christopher Lambert, Frank Surup, Seyed Akbar Khodaparast, Irmgard Krisai-Greilhuber, Hermann Voglmayr, Marc Stadler

                This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                Research Article
                Biodiversity & Conservation
                Evolutionary Ecology
                Molecular systematics


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