Systems and life history analysis of fungal adaptations to extreme environments

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Extremotolerant fungi occupy diverse niches that are exposed to severe stress and lack obvious nutrient sources. Prevalent examples of such niches in Canada include rock surfaces and semi-arid soils. Fungi employ a diverse array of strategies to successfully adapt to these stressful habitats, including slow growth, simplified morphologies, and the accumulation of protective pigments. Understanding the regulatory networks that coordinate these responses will provide valuable insight into the evolution of the extremophile lifestyle in the fungal kingdom. Moreover, comparison to other microbial and plant extremophiles will enable a broader perspective on how sessile organisms successfully adapt to and colonize harsh environments. Given the importance of fungi as a source of strains and enzymes used for industrial applications, better characterization of the mechanisms that promote adaptation to stressful habitats will also be likely to have applied significance. The objective of my research program is to investigate mechanisms that underlie the ability of the extremotolerant fungi such as Exophiala dermatitidis and Knufia petricola to adapt to stress and to secure adequate nutrition. Whereas the role of protective pigments such as carotenoids and melanin in mediating stress resistance has been established in these fungi, the regulatory pathways that direct the production of these pigments are poorly understood. Preliminary data generated by my lab shows that the conserved GTPase Cdc42 regulates light-induced carotenoid accumulation and have identified a conserved circadian regulator that likely coordinates the diurnal production of pigments and other stress responsive functions. I propose the use of genomic and genetic approaches to further investigate the role of light and circadian responses in the ability to tolerate stress (Aim #1). My lab has also succeeded in engineering artificial mutualisms with the alga Chlorella sorokiniana that enhance viability of E. dermatitidis. I propose to generate additional mutualisms and to use them to define key morphological and metabolic features that underlie the capacity of fungi to acquire nutrient from photoautotrophs (Aim #2). Lastly, my lab has begun to assemble a large collection of extremotolerant fungi, algae, and cyanobacteria from rock surfaces and biological soil crusts in Canada. I propose to expand and leverage this collection to determine the extent to which "transient lichenization" of photoautotrophs represents a general strategy used by extremotolerant fungi to secure nutrition in harsh ecosystems. My research program will provide a robust, cutting-edge training experience for up to 12 HQP (2 PhD, 2 MSc, 8 BSc). Our collective efforts over the next five years will generate unprecedented new insight into the adaptations that have expanded the terrestrial environments available for colonization by eukaryotic life.*****