Abstract: Pear fruit are often infected with Penicillium expansum during storage. Therefore, analyzing the regulatory mechanisms of relevant transcription factors on the defense of pear fruit against P. expansum are of great significance. Our previous research found that the transcription factor PbWRKY29 may play an important role in disease resistance in pear fruit. However, the underlying mechanism remains unclear. In this study, we conducted a bioinformatics-based analysis of the physicochemical properties of the PbWRKY29 protein and experimentally investigated its functional role and mechanism of action in pear fruit defense against P. expansum. Our results showed that the protein was composed of 20 amino acids and was characterized as an acidic, unstable, and highly hydrophilic non-transmembrane protein lacking a signal peptide, primarily localized to the nucleus. Its secondary structure comprises α-helices, extended strands, and random coils. Transient overexpression of PbWRKY29 in pear fruit enhanced the resistance to P. expansum. PbWRKY29 reinforces the resistance of pear fruit against P. expansum by positively regulating the expression of ethylene biosynthesis-related genes (PbACS1, PbACS7, PbACO1, PbACO2, and PbSAMB2) and defense-related genes (PRH, PRB1, and PRMS), thereby promoting the accumulation of H2O2, suppressing the production rate of superoxide anion radical, and enhancing the activities of antioxidant enzymes (CAT, SOD, POD, and PPO). These findings provide a new theoretical basis for an in-depth understanding of the molecular mechanisms underlying postharvest defense against P. expansum infection in pear fruit.

Key words: pear fruit; Penicillium expansum; biocontrol; PbWRKY29