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Olpidiopsis is a genus of obligate holocarpic endobiotic oomycetes. Most of the species classified in the genus are known only from their morphology and life cycle, and a few have been examined for their ultrastructure or molecular phylogeny. However, the taxonomic placement of all sequenced species is provisional, as no sequence data are available for the type species, O. saprolegniae, to consolidate the taxonomy of species currently placed in the genus. Thus, efforts were undertaken to isolate O. saprolegniae from its type host, Saprolegnia parasitica and to infer its phylogenetic placement based on 18S rDNA sequences. As most species of Olpidiopsis for which sequence data are available are from rhodophyte hosts, we have also isolated the type species of the rhodophyte-parasitic genus Pontisma, P. lagenidioides and obtained partial 18S rDNA sequences. Phylogenetic reconstructions in the current study revealed that O. saprolegniae from Saprolegnia parasitica forms a monophyletic group with a morphologically similar isolate from S. ferax, and a morphologically and phylogenetically more divergent species from S. terrestris. However, they were widely separated from a monophyletic, yet unsupported clade containing P. lagenidioides and red algal parasites previously classified in Olpidiopsis. Consequently, all holocarpic parasites in red algae should be considered to be members of the genus Pontisma as previously suggested by some researchers. In addition, a new species of Olpidiopsis, O. parthenogenetica is introduced to accommodate the pathogen of S. terrestris.
Holocarpic oomycetes are poorly known but widespread parasites in freshwater and marine ecosystems. Most of the holocarpic species seem to belong to clades that diverge before the two crown lineages of the oomycetes, the Saprolegniomycetes and the Peronosporomycetes. Recently, the genus Miracula was described to accommodate Miracula helgolandica, a holocarpic parasitoid of Pseudo-nitzschia diatoms, which received varying support for its placement as the earliest-diverging oomycete lineage. In the same phylogenetic reconstruction, Miracula helgolandica was grouped with some somewhat divergent sequences derived from environmental sequencing, indicating that Miracula would not remain monotypic. Here, a second species of Miracula is reported, which was found as a parasitoid in the limnic centric diatom Pleurosira leavis. Its life-cycle stages are described and depicted in this study and its phylogenetic placement in the genus Miracula revealed. As a consequence, the newly discovered species is introduced as Miracula moenusica.
Biosynthetic gene content of the "Perfume Lichens" Evernia prunastri and Pseudevernia furfuracea
(2019)
Lichen-forming fungi produce a vast number of unique natural products with a wide variety of biological activities and human uses. Although lichens have remarkable potential in natural product research and industry, the molecular mechanisms underlying the biosynthesis of lichen metabolites are poorly understood. Here we use genome mining and comparative genomics to assess biosynthetic gene clusters and their putative regulators in the genomes of two lichen-forming fungi, which have substantial commercial value in the perfume industry, Evernia prunastri and Pseudevernia furfuracea. We report a total of 80 biosynthetic gene clusters (polyketide synthases (PKS), non-ribosomal peptide synthetases and terpene synthases) in E. prunastri and 51 in P. furfuracea. We present an in-depth comparison of 11 clusters, which show high homology between the two species. A ketosynthase (KS) phylogeny shows that biosynthetic gene clusters from E. prunastri and P. furfuracea are widespread across the Fungi. The phylogeny includes 15 genomes of lichenized fungi and all fungal PKSs with known functions from the MIBiG database. Phylogenetically closely related KS domains predict not only similar PKS architecture but also similar cluster architecture. Our study highlights the untapped biosynthetic richness of lichen-forming fungi, provides new insights into lichen biosynthetic pathways and facilitates heterologous expression of lichen biosynthetic gene clusters.