Directed evolution of melanized fungi to investigate mechanisms of adaptation and resistance to ionizing radiation

Author:

Jillian Romsdahl 1, Zachary Schultzhaus 1, Amy Chen 2, Jing Liu 2, Alexander
Ewing 2, Jason Stajich 3, Zheng Wang 2

Author address:

1 National Research Council, Postdoctoral Research Associate, United States Naval Research Laboratory, Washington DC USA;
2 United States Naval Research, Center for Biomolecular Science and Engineering, Washington DC, USA
3 University of California, Departement of Microbiology and Plant Pathology, Washington DC, USA

Full conference title:

15th European Conference on Fungal Genetics 2020

Date: 21 June 2020

Abstract:

Lonizing radiation is highly damaging to biological systems and therefore represents a significant health threat. Despite efforts to prevent nuclear proliferation and increase safety at nuclear power plants, the risk of a nuclear disaster persists. Further, ionizing radiation present in cosmic rays introduces protective challenges for astronauts traveling past Earth’s magnetosphere. There is an unmet need for novel and effective radioprotective materials and prophylactic treatments that will protect humans from radiation exposure. Fungi, which are highly resistant to radiation and capable of surviving doses up to 1000x higher than mammals, are well-poised to serve as a model to investigate adaptation and resistance to ionizing radiation. In particular, melanized fungal species are often associated with highly irradiated environments, as melanin is considered an evolutionary derived trait that confers protection against radiation and extreme temperatures. However, recent studies suggest that fungal resistance to ionizing radiation is independent of melanin, implying the existence of unrealized adaptation and resistance mechanisms. To investigate these mechanisms, the melanized yeast Exophiala dermatitidis and the melanized filamentous fungus Aspergillus niger were adapted to various doses of γ-radiation. Whole-genome sequencing enabled the identification of genetic variations that had been selected for during directed evolution, which revealed “high-impact” frameshift and premature stop codon gain mutations in genes involved in DNA repair, transcriptional regulation, transmembrane transport, and protein ubiquitination. Genetic engineering was used to investigate the involvement of highly mutated genes on radiation resistance. These findings validate the use of melanized fungi as a model for studying adaptation and resistance to ionizing radiation and serve as a starting point for exploring novel radioprotective applications of such mechanisms.

Link to conference website:

Link Conference abstract:

ECFG 15