CbCBF2 Integrates JA and BR Signaling to Enhance Oleanolic Acid Biosynthesis in Conyza blinii H. Lév Under Cold Stress

Low temperature significantly contributes to the medicinal quality of Conyza blinii. The CBF/DREB1-dependent cold-responsive signaling pathway is a major contributor to plant cold stress resistance. However, whether the CBF/DREB1 signaling pathway affects the terpenoid metabolism of C. blinii under cold stress remains to be explored. Here, we systematically identified and analyzed the impact of CbCBFs on the terpenoid metabolism of C. blinii. The results showed that three CbCBFs and CbICE1 were identified based on the transcriptome. The functions significantly correlated with CbCBFs encompass plant hormones and stress responses. Co-expression analysis revealed that key genes in BR and JA signaling pathways were correlated with CbCBFs. Among them, CbCBF2 is the predominant factor under low-temperature conditions and is significantly positively correlated with oleanolic acid. Overexpression of CbCBF2 significantly upregulated the catalase gene CbβAS and increased oleanolic acid content in the leaves. These results indicate that CbCBF2 can act as a major regulatory factor to promote the synthesis of oleanolic acid by integrating JA and BR signaling under low temperature conditions.