In nature, plant roots are always colonized by fungi. This interaction can be either mutualistic, benefiting both the plant and the fungus, or pathogenic, where the fungus harms the host plant. A research group led by Professor Dr. Alga Zuccaro at the CEPLAS Cluster of Excellence has now deciphered how the beneficial root fungus Serendipita indica successfully colonizes plant roots of the model plant Arabidopsis thaliana.