Phosphoproteomic Insights into the Dynamic Responses of Maize ( Zea mays L.) to Setosphaeria turcica Infection

Northern corn leaf blight, caused by Setosphaeria turcica, poses a serious threat to global maize production. Although previous studies have documented protein expression changes during infection, the role of protein phosphorylation has remained unclear. Here, using mass spectrometry-based proteomics, we identified 2,691 phosphopeptides from 1,598 proteins, corresponding to 3,416 phosphorylation sites. Phosphorylation dynamics were largely independent of the protein abundance changes during infection. We also uncovered 21 enriched phosphorylation motifs, including a novel [LxxxxS] motif. Quantitative analysis revealed significant changes in phosphorylated proteins across infection stages, indicating a functional transition from initial metabolic and chromatin regulators to subsequent redox- and pathogen-responsive proteins. Notably, ZmRIN4b was shown to enhance the resistance by modulating reactive oxygen species and immune gene expression. Protein interaction network analysis highlighted ZmMYB2 as a central hub and implicated glycolysis/gluconeogenesis and chloroplast proteins in defense. These findings offer novel insights into the phosphorylation-mediated immune response of maize to S. turcica.