Our study focuses on sugar transporters from both plant and fungal partners at the symbiotic interface to better understand biotrophic exchange systems. Thereby, a collection of putative contigs and ESTs of hexose transporters from Medicago truncatula and Fragaria x ananassa will be processed. The full length sequences will be cloned for functional complementation and uptake experiments in transport deficient yeast mutants. This work also investigates the influence of different mycorrhizal fungi on (1) the expression level of sugar transporters and (2) the economically relevant part of F. x ananassa by analyzing its impact on the plant and the fruit. To this aim, combination of phenological observations, transcriptomics (qRT-PCR and Microarrays) and biochemical analyses will be performed. The need of the complete characterization of hexose transporters is reinforced by the recent demonstration of enhanced sugar content in mycorrhizal strawberries (G. Berta and G. Lingua; personal communication).