Functional ecology of the plant-fungus interface: harnessing evolutionary genomics, transcriptomics and experimental ecology to dissect communication and nutrient exchange in a mutualistic symbiosis
This proposal aims to construct an evolutionary framework for the molecular interactions between ectomycorrhizal fungi and their plant hosts. Ectomycorrhizal (ECM) symbiosis is a mutualistic association between fungi and trees that is founded on reciprocal exchange of nutrients, facilitating growth in nutrient-limited or otherwise stressful environments. The symbiosis has evolved independently in many fungal clades, raising questions about its evolvability and the ecological redundancy of different ECM fungi. The ability of one ECM fungus to functionally replace another is especially salient in light of environmental change and loss of biodiversity. What components of communication between fungus and plant are conserved among ECM species? How conserved are molecular interactions at different phylogenetic scales? What are the molecular mechanisms responsible for phenotypic variation? ECM fungi from the genus Amanita will be grown together with the host Quercus robur (pendunculate oak). Q. robur displays endogenous rhythmic growth with alternating root and shoot flushes, distinct physiological states of growth that influence interactions with ECM fungi. The fungal strains are selected to survey variation i) between different Amanita ECM species and ii) in comparison with closely related saprobic Amanita sp., using a phylogenomic approach. We will profile genes expressed on both fungal and plant side at different time points: during mycorrhizal development and in mature mycorrhizas, while separating each time point into periods of root flush and shoot flush. We will profile a compendium of traits related to the functioning and success of ECM symbiosis at each developmental stage. Together these results will allow us to develop a detailed mechanistic view of the genes and pathways underlying ECM symbiosis, their evolutionary dynamics across a phylogenetic gradient of fungal partners and their impact on the different physiological stages of plant growth.