Mechanisms of Differential Resource Uptake and Translocation in <i>Agaricus bisporus</i>

Mushroom-forming fungi form interconnected networks of hyphae and cords that cooperate to colonise their environment and feed developing mushrooms. To fully enable this cooperation, transport across the network is essential for the collection and delivery of resources when and where needed. It is not known to what extent, and with which resources, specific parts of the network contribute to feeding the developing mycelium and mushrooms. In this study, we investigated the translocation patterns of water, carbon and nitrogen in Agaricus bisporus, using stable isotope tracers. Ammonium-derived ¹⁵N, but not glucose-derived ¹³C, was consistently transported from the centre to the periphery of colonies in axenic culturing conditions. External wicking along the hyphae is likely a major translocation mechanism. Throughout the compost bed, there was ¹³C and ¹⁵N transport towards the mycelium colonising the casing and the developing mushrooms. Moreover, the top compost layer contributed most to feeding the growing mushrooms, irrespective of the mycelium network architecture. Within cords, we found five cell types of which one is likely specialised for nutrient transport. Overall, these findings provide new insights into nutrient uptake and translocation mechanisms in A. bisporus. This knowledge may ultimately enable enhanced feeding of mushrooms to improve production efficiency.