Identifying substrate triggers for appressorium development in Setosphaeria turcica and functional characterization...

Northern corn leaf blight is a devastating disease caused by Setosphaeria turcica (S. turcica), leading to significant yield losses in maize. S. turcica initiates infection through a specialized structure known as the appressorium, which only forms on conducive substrates. In this study, we introduce a semi‑silicone water polyurethane resin (Si-PUD) that induces only germ tube formation from S. turcica conidia. A mixed coating of Si-PUD and polytetrafluoroethylene successfully triggers appressorium formation. Both coatings maintain optical transparency, chemical resistance, and thermal stability, which facilitate microscopic observations and the development of high-throughput systems. These coatings also demonstrate similar effects on Bipolaris maydis (B. maydis), suggesting their potential universal applicability. Utilizing coating-induced synchronous appressorium formation and proteomic analyses, we identified five genes essential for S. turcica appressorium development. Functional analyses of two zinc binuclear cluster domain-containing transcription factors, StTF1 and StTF2, revealed their critical roles in appressorium development and pathogenicity. This study not only develops a novel method for inducing appressorium formation but also lays the groundwork for rapid screening of environmentally-friendly fungicides that inhibit appressorium development.