Evolution of lichen-forming fungi, algae, and secondary metabolites

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Large expanses of lichens that cover northern ecosystems form a mosaic of interactions (symbioses) between algae and fungi (symbionts). The widespread success of these lichens may be attributed to the algal symbiont and fungal secondary metabolites (polyketides). Algal carbohydrates from photosynthesis are transferred to the fungal partner and used in polyketide synthesis. Polyketides have ecological benefits such as light screening and antimicrobial activity that help the lichen survive in its habitat, but they may also have applications in biotechnology. The long-term goal of this research program is to understand the functional ecology and evolution of lichen symbionts and their polyketides in lichen dominated habitats. I will investigate ecological patterns in the algal symbiont and fungal polyketide production in 4 Cladonia species distributed among continental and coastal habitats. The varied chemotypes of these species will test hypotheses for 2 MSc projects that the algal symbiont and climate influence polyketide production. Since the alga is essential for the lichen symbiosis, polyketides that help protect the alga from adverse conditions should be produced in early stages of the symbiont interaction. Therefore, my second objective for a PhD and 2 BSc projects is to compare transcriptionally active PKS genes in 2 culture treatments; the fungus growing alone and the fungus and alga interacting together. This study will reveal active PKS genes in the presence and absence of the alga. Since growing conditions have been hypothesized to affect polyketide production, the third objective for a PhD, 3 BSc, and PDF projects is to compare transcriptomes from C. rangiferina grown under different conditions to identify the differentially transcribed PKS genes providing insights into gene function leading to further biotechnology studies. My research program has provided a better understanding of the evolutionary and adaptive strategies of lichen symbioses in lichen-dominated habitats but this proposed research will address the role of the alga in polyketide synthesis, establish PKS gene transcription at early stages in the interaction, and examine ecological benefits and isolation of PKS genes for biotechnology. Ten HQP are integrated within the proposed research for training in leading edge technology on topics addressing current day issues discovery of new bioactive molecules and impact of environmental change on the maintenance of arctic biodiversity.