In this project, we conducted a quantitative analysis of secreted proteins during the initial stages of the pathogenic program in Ustilago maydis. We utilized the AB33 strain, which contains the compatible bE2/bW1 genes controlled by the nitrate-inducible nar1 promoter. Consequently, in nitrogen-rich media, the virulence program is initiated, leading to the development of filaments. Filamentation was induced for 5 hours in minimal medium supplemented with NO3 (MM-NO3) in both the AB33 wild-type and Δrow1 strains. Subsequently, samples were collected, precipitated, processed, and analyzed.