Recent progress in marine mycological research in different countries, and prospects for future developments worldwide

Early research on marine fungi was mostly descriptive, with an emphasis on their diversity and taxonomy, especially of those collected at rocky shores on seaweeds and driftwood. Subsequently, further substrata (e.g. salt marsh grasses, marine animals, seagrasses, sea foam, seawater, sediment) and habitats (coral reefs, deep-sea, hydrothermal vents, mangroves, sandy beaches, salt marshes) were explored for marine fungi. In parallel, research areas have broadened from micro-morphology to ultrastructure, ecophysiology, molecular phylogenetics, biogeography, biodeterioration, biodegradation, bioprospecting, genomics, proteomics, transcriptomics and metabolomics. Although marine fungi only constitute a small fraction of the global mycota, new species of marine fungi continue to be described from new hosts/substrata of unexplored locations/habitats, and novel bioactive metabolites have been discovered in the last two decades, warranting a greater collaborative research effort. Marine fungi of Africa, the Americas and Australasia are under-explored, while marine Chytridiomycota and allied taxa, fungi associated with marine animals, the functional roles of fungi in the sea, and the impacts of climate change on marine fungi are some of the topics needing more attention. In this article, currently active marine mycologists from different countries have written on the history and current state of marine fungal research in individual countries highlighting their strength in the subject, and this represents a first step towards a collaborative inter- and transdisciplinary research strategy

A new method to identify flanking sequence tags in <it>chlamydomonas</it> using 3’-RACE

Abstract Background The green alga Chlamydomonas reinhardtii, although a premier model organism in biology, still lacks extensive insertion mutant libraries with well-identified Flanking Sequence Tags (FSTs). Rapid and efficient methods are needed for FST retrieval. Results Here, we present a novel method to identify FSTs in insertional mutants of Chlamydomonas. Transformants can be obtained with a resistance cassette lacking a 3’ untranslated region (UTR), suggesting that the RNA that is produced from the resistance marker terminates in the flanking genome when it encounters a cleavage/polyadenylation signal. We have used a robust 3’-RACE method to specifically amplify such chimeric cDNAs. Out of 38 randomly chosen transformants, 27 (71%) yielded valid FSTs, of which 23 could be unambiguously mapped to the genome. Eighteen of the mutants lie within a predicted gene. All but two of the intragenic insertions occur in the sense orientation with respect to transcription, suggesting a bias against situations of convergent transcription. Among the 14 insertion sites tested by genomic PCR, 12 could be confirmed. Among these are insertions in genes coding for PSBS3 (possibly involved in non-photochemical quenching), the NimA-related protein kinase CNK2, the mono-dehydroascorbate reductase MDAR1, the phosphoglycerate mutase PGM5 etc.. Conclusion We propose that our 3’-RACE FST method can be used to build large scale FST libraries in Chlamydomonas and other transformable organisms.</p

Halogenation in Fungi: What Do We Know and What Remains to Be Discovered?

International audienceIn nature, living organisms produce a wide variety of specialized metabolites to perform many biological functions. Among these specialized metabolites, some carry halogen atoms on their structure, which can modify their chemical characteristics. Research into this type of molecule has focused on how organisms incorporate these atoms into specialized metabolites. Several families of enzymes have been described gathering metalloenzymes, flavoproteins, or S-adenosyl-L-methionine (SAM) enzymes that can incorporate these atoms into different types of chemical structures. However, even though the first halogenation enzyme was discovered in a fungus, this clade is still lagging behind other clades such as bacteria, where many enzymes have been discovered. This review will therefore focus on all halogenation enzymes that have been described in fungi and their associated metabolites by searching for proteins available in databases, but also by using all the available fungal genomes. In the second part of the review, the chemical diversity of halogenated molecules found in fungi will be discussed. This will allow the highlighting of halogenation mechanisms that are still unknown today, therefore, highlighting potentially new unknown halogenation enzymes

Penicillium roqueforti PR toxin gene cluster characterization

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Enzymatic bromination of marine fungal extracts for enhancement of chemical diversity

Highlights: • Using a vHPO is efficient in increasing chemical diversity of natural extracts. • vHPO are a sustainable strategy to catalyze unspecific halogenation. • Metabolomics and bioinformatics are effective tools to highlight relevant molecules. • 12-bromo-communesin A is a novel brominated molecule with antimicrobial activity. This study reports for the first time the use of a vanadium chloroperoxidase (vCPO) enzyme to increase the chemical diversity of marine fungal extracts to generate new natural chemical entities. The vCPO used is a recombinant protein from the marine fungus Hortaea werneckii (HwvCPO). It catalyzes the formation of hypohalous acid (HOX), a highly reactive compound that can react with electron-rich substrates. Here, four fungal extracts obtained from different marine fungal strains (Penicillium expansum, Aspergillus pseudoglaucus, Trichoderma sp. and Hortaea werneckii) were investigated for enhancement of their chemical diversity. The metabolomic study showed that the enzymatic treatment of extracts of P. expansum and A. pseudoglaucus significantly boosted the chemodiversity by increasing the number of halogenated molecules. Indeed, respectively 5.07 and 6.65 times more halogenated ions were detected in ESI-MS profile of the extracts compared to negative controls. The new chemistry generated allowed the identification of new brominated compounds, one of which was further purified and characterized as 12-bromo-communesin A (2). This new compound, in contrast to communesin A (1), exhibited moderate antimicrobial activity on the methillicin-resistant Staphylococcus aureus (IC50 of 62 μM). This study has clearly demonstrated the employment of the vCPO enzyme to be a promising and environmentally friendly strategy to enhance the chemical diversity of natural extracts

Deep Subseafloor Fungi as an Untapped Reservoir of Amphipathic Antimicrobial Compounds

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The Bacterial Vanadium Iodoperoxidase from the Marine Flavobacteriaceae Zobellia galactanivorans Reveals Novel Molecular and Evolutionary Features of Halide Specificity in this Enzyme Family

International audienceVanadium haloperoxidases (VHPO) are key enzymes that oxidize halides and are involved in the biosynthesis of organo-halogens. Until now, only chloroperoxidases (VCPO) and bromoperoxidases (VBPO) have been characterized structurally, mainly from eukaryotic species. Three putative VHPO genes were predicted in the genome of the flavobacterium Zobellia galactanivorans, a marine bacterium associated with macroalgae. In a phylogenetic analysis, these putative bacterial VHPO were closely related to other VHPO from diverse bacterial phyla but clustered independently from eukaryotic algal VBPO and fungal VCPO. Two of these bacterial VHPO, heterogeneously produced in Escherichia coli, were found to be strictly specific for iodide oxidation. The crystal structure of one of these vanadium-dependent iodoperoxidases, Zg-VIPO1, was solved by multiwavelength anomalous diffraction at 1.8 Å, revealing a monomeric structure mainly folded into α-helices. This three-dimensional structure is relatively similar to those of VCPO of the fungus Curvularia inaequalis and of Streptomyces sp. and is superimposable onto the dimeric structure of algal VBPO. Surprisingly, the vanadate binding site of Zg-VIPO1 is strictly conserved with the fungal VCPO active site. Using site-directed mutagenesis, we showed that specific amino acids and the associated hydrogen bonding network around the vanadate center are essential for the catalytic properties and also the iodide specificity of Zg-VIPO1. Altogether, phylogeny and structure-function data support the finding that iodoperoxidase activities evolved independently in bacterial and algal lineages, and this sheds light on the evolution of the VHPO enzyme family