Fungal-plant signalling in the Ustilago maydis-maize pathosystem

The smut fungus Ustilago maydis needs the host plant maize for completion o f its sexual life cycle. Recent experiments highlight the importance of cAM P and mitogen-activated protein (MAP) kinase signalling for cell fusion as well as for subsequent stages of plant colonisation and induction of diseas e symptoms. During these distinct developmental stages the same signalling cascades must be differentially regulated and accommodate multiple inputs a nd outputs.