Researchers studied how blue light triggers brown film formation on shiitake mushroom mycelia by analyzing protein modifications called phosphorylation. Using advanced mass spectrometry techniques, they identified thousands of phosphorylation changes in proteins when mushroom mycelia are exposed to blue light. The findings revealed that blue light activates several important processes including light sensing, pigment production, and cell wall degradation, providing insights into how mushrooms develop fruiting bodies in response to light signals.