Transcriptomic Analysis of the Role of PcPdeH in Chilli Pepper Infection by Phytophthora capsici

Phytophthora blight, caused by Phytophthora capsici , is a devastating disease that threatens pepper fruit production worldwide. PcPdeH, a high‐affinity phosphodiesterase in the cAMP signalling pathway, is essential for P. capsici vegetative growth, the oxidative stress response and pathogenicity. To explore the regulatory role of PcPdeH in pathogenicity, we conducted a transcriptomic analysis comparing gene expression between the PcPdeH knockout mutant and wild‐type strains during mycelial growth, 3 h post infection (hpi) and 12 hpi. The results demonstrated that disruption of PcPdeH significantly downregulated genes associated with hydrolase activity, carbohydrate metabolic processes, oxidoreductase activity and key metabolic pathways, including starch and sucrose metabolism, glycolysis, chloroalkane and chloroalkene degradation and fatty acid degradation. Functional enrichment analysis revealed that PcPdeH plays a regulatory role in metabolic adaptation and oxidative stress tolerance through the cAMP signalling pathway. These findings position PcPdeH as a central regulator within the cAMP signalling network of P. capsici , linking it to virulence‐related processes and highlighting its potential as a target for disease management strategies.