The volatile sesquiterpene β-caryophyllene generated by the Phoebe bournei terpene synthase PbTPSa21 regulates seed germination by mediating ROS signaling

Phoebe bournei is an evergreen tree with high economic and social value because of its fine timber and pleasant aroma, which is predominantly produced by terpenoids, including β-caryophyllene. However, the natural reproduction and artificial cultivation of P. bournei are severely hindered by long seed dormancy times and poor seed fragility. Terpenoids are secondary metabolites with vast commercial application potential in medicine, agriculture, and gardening, but their role in seed germination remains elusive. Here, we identified a novel P. bournei β-caryophyllene synthase gene, PbTPSa21, whose overexpression improved β-caryophyllene biosynthesis and seed germination in Arabidopsis. Through analyses of the morphological and physiological changes in Arabidopsis and P. bournei seeds during germination under different concentrations of exogenous β-caryophyllene, we found that β-caryophyllene improved seed vigor and germination in a concentration-dependent manner. Transcriptomic analysis revealed a regulatory network of β-caryophyllene signaling via gene coexpression analysis. Genes related to reactive oxygen species (ROS) signaling were found to be differentially regulated upon β-caryophyllene treatment. The results of dihydroethidium (DHE) staining analysis suggested a negative correlation between the concentration of β-caryophyllene and the level of ROS in the radicle. Further treatments with ROS modulators revealed that β-caryophyllene functions as an ROS scavenger in the regulation of seed germination. This study reveals the role of β-caryophyllene in seed germination via ROS scavenging and provides valuable resources for modulating plant growth and development.