The Basic Leucine Zipper Transcription Factor PlBZP32 Associated with the Oxidative Stress Response Is Critical for Pathogenicity of the Lychee Downy Blight Oomycete Peronophythora litchii.

Basic leucine zipper (bZIP) transcription factors are widespread in eukaryotes, including plants, animals, fungi, and oomycetes. However, the functions of bZIPs in oomycetes are rarely known. In this study, we identified a bZIP protein possessing a special bZIP-PAS structure in , named We found that is upregulated in zoospores, in cysts, and during invasive hyphal growth. We studied the functions of using the RNAi technique to suppress the expression of this gene. -silenced mutants were more sensitive to oxidative stress, showed a lower cyst germination rate, and produced more sporangia than the wild-type strain SHS3. The -silenced mutants were also less invasive on the host plant. Furthermore, we analyzed the activities of extracellular peroxidases and laccases and found that silencing decreased the activities of peroxidase and laccase. To our knowledge, this is the first report that the functions of a bZIP-PAS protein are associated with oxidative stress, asexual development, and pathogenicity in oomycetes. In this study, we utilized the RNAi technique to investigate the functions of PlBZP32, which possesses a basic leucine zipper (bZIP)-PAS structure, and provided insights into the contributions of bZIP transcription factors to oxidative stress, the production of sporangia, the germination of cysts, and the pathogenicity of This study also revealed the role of PlBZP32 in regulating the enzymatic activities of extracellular peroxidases and laccases in the plant-pathogenic oomycete.