Study on the molecular mechanism of Penicillium expansum bZIP transcription factor PebZIP7 in apple infection

Penicillium expansum is the main pathogen causing postharvest decay of apples, resulting in economic losses during fruit storage. Meanwhile, patulin, a highly toxic secondary metabolite produced by the pathogen, poses a significant threat to food safety. Investigating its pathogenic molecular mechanisms can provide theoretical support for disease control. To elucidate the transcriptional regulatory mechanism of the key pathogenic gene PeBgl1, this study screened transcriptome data to identify the bZIP family transcription factor PebZIP7 (PEX2_056,300) with a gene expression pattern similar to PeBgl1. Using yeast one-hybrid, dual-luciferase reporter gene, and electrophoretic mobility shift assay (EMSA) experiments, it was verified both in vivo and in vitro that PebZIP7 can specifically bind to the PeBgl1 promoter and positively regulate its expression. Gene knockout tests showed that after PebZIP7 was deleted, the pathogenicity of P. expansum toward apples was significantly weakened, and both the fruit decay rate and decay diameter were lower than those of the wild-type strain and the complemented strain. Further functional analysis revealed that PebZIP7 can positively regulate the sporulation capacity of the strain while specifically negatively regulating the strain's tolerance to low temperature, cell membrane stress, and oxidative stress. This study clarifies the biological functions of PebZIP7 in P. expansum infection, growth and development, and stress responses, enriches the research on transcriptional regulation in P. expansum, and provides a reference and candidate target for the green control of postharvest blue mold in apples.