During colony establishment, germinating spores of N. crassa mutually attract each other, establish physical contact and undergo cell fusion. A combination of live-cell imaging and molecular genetic analysis revealed an unusual mode of cell-cell signaling controlling this interaction. During directed growth, the MAP kinase MAK-2 localizes to the cell tips of interacting germlings in a highly dynamic, oscillatory manner. We hypothesize that the cells undergo a kind of "cell dialog", in which both partners alternate between signal sending and signal receiving. To further understand the molecular basis mediating intercellular communication and fusion, we functionally characterize genes required for this process. By means of fluorescence microscopy, we determine the subcellular localization of proteins during germling fusion and, thus, can explore their function within the cells. These studies will extend our knowledge about cell-cell signaling in filamentous fungi and, more general, in eukaryotic organisms.
Recently, we have begun to study the interactions between different species on a cellular level. The dialogue-like communication mechanism, which mediates cell–cell fusion in filamentous fungi, is a conserved complex trait. This mechanism allows communication and behavioral coordination between cells of distantly related species. It sheds light on microbial communication and the potential for horizontal gene transfer in fungi. The mechanisms and outcomes of interspecies fungal interactions are in general only very poorly understood but potentially of very high relevance. We have recently shown, that the presence of N. crassa reduces the virulence of B. cinerea on different host plants by a so far unknown mechanism.
Shifting our focus to the broader ecological context, we recognize the pivotal role of forests in maintaining ecological balance, carbon sequestration, and biodiversity support. However, climate change poses unprecedented challenges to forest ecosystems.
Conifer tip blight, caused by Diplodia sapinea, exemplifies latent pathogens evolving into major threats globally in the context of climate change. The likely, but so far only poorly characterized triggers for the shift to pathogenic growth include reduced plant resistance due to climate change-induced stressors, such as drought and prolonged heat waves
Drawing on our fungal model organism expertise, we are establishing D. sapinea as a pioneering model for latent tree pathogens. Transformation protocols allow us to create fluorescent protein-expressing mutants, enabling precise imaging of infection processes and targeted gene modifications. We can now experimentally test hypotheses derived from decades of intensive work on the organism in its natural environment on a small scale in the laboratory. Our goal is to understand the cellular mechanisms underlying the outbreak of Diplodia tip blight and the influence of the surrounding microbiome on the processes.