Desiccator assay and sulfur labeling experiment
Twenty-one 10-d old Arabidopsis seedlings germinated on MS were transferred to a Petri dish with sucrose-free MS medium (14.5 cm in diameter). In a 2.5 L desiccator, a 7-d old fungal culture grown on PDA was placed at the bottom. A plastic inlay with holes was inserted in the middle of the desiccator, and the big Petri-dish with seedlings was placed on top of it. To ensure sterility of the experiment, the seam of the desiccator was wrapped with 3MTM Micropore tape (Figure S2). Fungus and seedlings were incubated at 22 °C under long day conditions (16 hours light/ 8 hours dark; 80 μmol m−2s−1) for 14 days. Number of inflorescence (flower stalk) and shoot fresh weight were measured.
The same procedure was followed for sulfur labeling experiments, in which a 7-d old M. hyalina culture grown on labeled/unlabeled KM medium and 16 10-d old Arabidopsis seedlings were used. Root and shoot tissues were collected after 14 days for analysis.