Movie S3.

After interacting germlings have touched, the MAP kinase MAK-1 is recruited to the site of cell–cell fusion. Two germlings of a strain expressing MAK-1-GFP (NCAL010-1) interact and fuse with each other. The protein localizes to the cytosol and is enriched in the nuclei. Upon physical contact, the MAP kinase is strongly recruited to the site of cell–cell fusion. MAK-1-GFP transiently forms a ring-like structure through which individual nuclei can pass. (Scale bar, 5 μm.)