Perillaldehyde controls citrus green mold by inhibiting the ribosome biogenesis of Penicillium digitatum and improving citrus disease resistance

Perillaldehyde (PAE) is a green and safe active ingredient of natural plants. The inhibitory activity of PAE against the citrus postharvest pathogen Penicillium digitatum and its ability to control green mold were evaluated by in vitro and in vivo experiments. The results revealed that the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) of PAE against P. digitatum were 0.5 and 1 μL/mL, respectively. The results of conductivity, cell activity staining, and calcium fluoride white staining revealed that PAE damaged the membrane and cell wall integrity of P. digitatum . PAE promoted ROS accumulation in P. digitatum , as shown by 2',7'-Dichlorofluorescein diacetate (DCHF-DA) staining, which may induce cell death. To further investigate the molecular regulatory network of PAE in P. digitatum , we performed an RNA-sequencing analysis. The results displayed that differentially expressed genes were significantly enriched in the biogenetic pathway of ribosomes, and all of these genes were downregulated, suggesting that PAE treatment interfered with ribosome biogenesis in P. digitatum and inhibited the normal life processes of cells. Furthermore, PAE treatment reduced the incidence and severity of citrus green mold, and the overall control effect of the PAE treatment group with 5 × MFC was greater than that with 10 × MFC. Therefore, we determined the activity of enzymes related to fruit disease resistance. The results revealed that PAE treatment significantly increased the activities of CAT, POD, and PAL in citrus. These findings demonstrate that PAE prevents green mold disease by increasing the activity of citrus disease-resistant enzymes.