The role of ectomycorrhizal (ECM) fungi in biological mineral weathering is increasingly recognised, although the quantitative significance of microbially mediated mineral dissolution for plant growth is debated. Species within the ECM genus Suillus are found to preferentially inhabit mineral soils and are frequently reported to possess mineral weathering capabilities and take up base cations – nutrients derived from minerals. Though studies growing ECM fungi with minerals have shown heightened mycelial nutrient content compared to growth without minerals, the mechanistic understanding of nutrient mobilisation associated with weathering remains largely unknown. Here, we attempt to elucidate the mechanisms of base cation uptake, as essential process that follows mineral weathering. Previously, we have studied base cation transporter gene family copy number evolution and base cation uptake by Suillus species following a period of mineral weathering. Here we assess gene expression in Suillus species grown in pure culture and in symbiosis with Pinus sylvestris seedlings when grown with and without minerals in controlled lab conditions. In particular, we will focus on the differential expression of base cation transporter genes in the different treatments. We hypothesise that base cation transporter genes will be upregulated in treatments with minerals compared to those without.