Impact of Zn on the ectomycorrhizal interaction of Laccaria bicolor and populus tremula x alba 717-1B4

Ectomycorrhizal fungi (ECM) are an important group of organisms that ensure that trees can flourish in all types of environmental conditions. By providing nutrients, water and protection against stress conditions in exchange for sugars, they allow their host trees to grow. Understanding how ECM fungi respond to environmental stress-induced ROS, the regulation of Zn transporters and how this affects their symbiosis forming capabilities, remains understudied. Here, the response of the ECM fungus Laccaria bicolor to Zn stress in the presence of a poplar host plant is investigated. The transcriptional response to Zn excess/deficiency, as well as the ROS response, and the effect on symbiosis development is studied through qPCR, enzyme assays and fluorescence microscopy. While symbiosis development has already been found to induce ROS-producing stress for the fungus, it is unclear how the addition of Zn stress during symbiosis development influences L. bicolor and its capability to function as a symbiont. Preliminary results indicate a differential expression of ROS scavenging enzymes (CAT and SOD) due to the Zn stress and stress caused by the presence of the host plant. Root analysis also indicates more root tips are formed by the plant under Zn deficiency than the control, and less are formed during Zn excess. These results help us understand how this fungus adapts to combat two different stress conditions, Zn stress and symbiosis development, as well as further adjust its transcriptional profile for nutrient exchange with the poplar host plant, while also protecting the host from the Zn stress conditions.