Transcriptional acclimation and spatial differentiation characterize drought response by the ectomycorrhizal fungus Suillus pungens.

Increasing temperature and decreasing precipitation has led to more frequent and extreme drought events in many regions throughout the world. In the western United States, multi-year drought events have led to widespread plant mortality and extreme wildfires (Asner et al. 2016, Pickrell and Pennisi 2020). Communities of ectomycorrhizal fungi (EMF) - root symbionts which play a critical role in forest health - are also thought to be threatened by these climatic changes (Fernandez et al. 2017, Steidinger et al. 2019). However, altered soil moisture conditions have complex direct and indirect effects on both fungi and ecosystem processes, such as nutrient availability (Schimel 2018), making it difficult to elucidate the primary drivers of community composition based on field observations or experiments (Pena and Polle 2014). As a result, efforts to identify the genes or traits involved in response to drought events are critical for accurate prediction of future EMF composition and function (Allison and Treseder 2008, Romero-Olivares et al. 2019). Despite this fact, we are not aware of any studies that have used gene expression analyses to measure the response of individual EMF to drought events or other climatic stressors.