Integrated Transcriptomic and Metabolomic Analysis Reveals the Mechanism of Gibberillic acid Regulates the Growth and Flavonoid Synthesis in Phellodendron chinense Schneid Seedlings.

The phytohormone gibberellic acids (GAs) play a crucial role in the processes of growth, organ development, and secondary metabolism. However, the mechanism of exogenous GA 3 regulating the growth and flavonoid synthesis in Phellodendron chinense Schneid ( P. chinense Schneid) seedlings remains unclear. In this study, the physicochemical properties, gene expression level, and secondary metabolite of P. chinense Schneid seedlings under GA 3 treatment were investigated. The results showed that GA 3 significantly improved the plant height, ground diameter, fresh weight, chlorophyll content, soluble substance content, superoxide dismutase, and peroxidase activities. This was accompanied by elevated relative expression levels of Pc(S)-GA2ox , Pc(S)-DELLA , Pc(S)-SAUR50 , Pc(S)-PsaD , Pc(S)-Psb 27 , Pc(S)-PGK , Pc(S)-CER3, and Pc(S)-FBA unigenes. Conversely, a notable reduction was observed in the carotenoid content, catalase activity and the relative expression abundances of Pc(S)-KAO, Pc(S)-GID1 / 2, and Pc(S)-GH 3.6 unigenes in leaves of P. chinense Schneid seedlings ( p < 0.05). Furthermore, GA 3 evidently decreased the contents of pinocembrin, pinobanksin, isosakuranetin, naringin, naringenin, (-)-epicatechin, tricetin, luteolin, and vitexin belonged to flavonoid in stem bark of P. chinense Schneid seedlings ( p < 0.05). These results indicated that exogenous GA 3 promoted growth through improving chlorophyll content and gene expression in photosynthesis and phytohormone signal pathway and inhibited flavonoid synthesis in P. chinense Schneid seedlings.