Spatio-temporal MAPK dynamics mediate cell behavior coordination during fungal somatic cell fusion

Mitogen-activated protein kinases are conserved regulators of proliferation, differentiation and adaptation in eukaryotic cells. Their activity often involves changes in their subcellular localization, indicating an important role of these spatio-temporal dynamics for signal transmission. A striking model illustrating these dynamics is somatic cell fusion in Neurospora crassa . Germinating spores of this fungus rapidly alternate between signal sending and receiving, thereby establishing a kind of cell-cell dialog, which involves the alternating membrane recruitment of the MAP kinase MAK-2 in both fusion partners. Here we show that the dynamic translocation of MAK-2 is essential for coordinating the fusion partners behavior before physical contact. Activation and function of the kinase strongly correlate with its subcellular localization, indicating a crucial contribution of the MAP kinase dynamics in establishing regulatory feedback loops, which establish the oscillatory signaling mode. In addition, we provide evidence that MAK-2 not only contributes to cell-cell communication, but also mediates cell-cell fusion. The MAK-2 dynamics significantly differ between these two processes, suggesting a role of the MAP kinase in switching of the cellular programm between communication and fusion.