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

Abstract

BackgroundNodulisporic 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 ResultsInferences 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 SignificanceKnowledge 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.

Resurrection and emendation of the Hypoxylaceae, recognised from a multigene phylogeny of the Xylariales

“…None of them has so far been encountered in another xylariaceous species, let alone any other fungus, even though some yet unidentified metabolites with cohaerin-like UV/visible spectra were detected in the stromata of certain species of Hypoxylon (cf. H. pulicicidum, Bills et al 2012). A recent extensive study by Kuhnert et al (2016) embarked on these data.…”

Hypoxyvermelhotins A–C, new pigments from Hypoxylon lechatii sp. nov

“…Amplification products were purified using Nucleo Spin Gel and PCR Clean Up (Macherey-Nagel, Düren, Germany) as specified in the manufacturers' recommendations. 39 sequences of each gene originating from reliable sources (Bills et al 2012, Bitzer et al 2008, Hsieh et al 2005, Kuhnert et al 2013 were used in addition for phylogenetic analysis. Details on the considered specimens are given in Table 1.…”

Antimycobacterial dihydronaphthalenone from the endophytic fungus Nodulisporium sp. of Antidesma ghaesembilla

“…Nodulisporium, a common group of xylariaceous anamorphic fungi (Bills et al, 2012), is known to produce bioactive secondary metabolites such as cytotoxic and antimycobacterial quinones (Pontius et al, 2008), antibiotic naphthalenones (Isaka et al, 2009;Pittayakhajonwut et al, 2008), cytotoxic polyketides (Shiono et al, 2012), antifungal and antibiotic terpenoids , and antimalarial coumarins (Chinworrungsee et al, 2001). Our chemical investigation for bioactive secondary metabolites from the endophytic fungus Nodulisporium sp.…”