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Front. Microbiol. | doi: 10.3389/fmicb.2018.03161

Chemically-mediated interactions between macroalgae, their fungal endophytes, and protistan pathogens

  • 1Muséum national d'Histoire naturelle (France), France
  • 2Station Biologique de Roscoff, France
  • 3Max Planck for Chemical Ecology, Germany
  • 4Scottish Association For Marine Science, United Kingdom
  • 5Kongju National University, South Korea

Filamentous fungi asymptomatically colonise the inner tissues of macroalgae, yet their ecological roles remain largely underexplored. Here, we tested if metabolites produced by fungal endophytes might protect their host against a phylogenetically broad spectrum of protistan pathogens. Accordingly, the cultivable fungal endophytes of four brown algal species were isolated and identified based on LSU and SSU sequencing. The fungal metabolomes were tested for their ability to reduce the infection by protistan pathogens in the algal model Ectocarpus siliculosus. The most active metabolomes effective against the oomycetes Eurychasma dicksonii and Anisolpidium ectocarpii, and the phytomixid Maullinia ectocarpii were further characterized chemically. Several pyrenocines isolated from Phaeosphaeria sp. AN596H efficiently inhibited the infection by all abovementioned pathogens. Strikingly, these compounds also inhibited the infection of nori (Pyropia yezoensis) against its two most devastating oomycete pathogens, Olpidiopsis pyropiae and Pythium porphyrae. We thus demonstrate that fungal endophytes associated with brown algae produce bioactive metabolites which might confer protection against pathogen infection. These results highlight the potential of metabolites to finely-tune the outcome of molecular interactions between algae, their endophytes and protistan pathogens. This also provide proof-of-concept towards the applicability of such metabolites in marine aquaculture to control otherwise untreatable diseases.

Keywords: fungal endophyte, Macroalga (seaweed), Metabolome, molecular interaction, Protistan pathogen

Received: 18 Sep 2018; Accepted: 06 Dec 2018.

Edited by:

Marcelino T. Suzuki, Sorbonne Universités, France

Reviewed by:

Ekaterina Shelest, German Center for Integrative Biodiversity Research, Germany
Ravindra N. Kharwar, Banaras Hindu University, India  

Copyright: © 2018 Prado, Strittmatter, Dupont, Hubas, Vallet, Murua, Lacoste, Kim and Gachon. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Soizic Prado, Muséum national d'Histoire naturelle (France), Paris, France,