Comparative transcriptome analysis reveals the potential stimulatory mechanism of terpene trilactone biosynthesis by exogenous salicylic acid in Ginkgo biloba

Salicylic acid (SA) is an important endogenous signaling molecule that can not only induce disease resistance but also improve the accumulation of secondary metabolites in plants. Terpene trilactones (TTLs) are unique bioactive components of Ginkgo biloba L. and it can antagonize platelet activating factors. In this study, SA treatment could increase TTL content as well as increase several other physiological indicators related to growth, photosynthetic parameters, starch and sucrose content, antioxidant enzyme activity, and endogenous hormone content in G. biloba. Furthermore, comparative transcriptome analysis between the SA-treated and control was used to reveal the molecular regulation of SA on TTL biosynthesis. RNA-Seq analysis identified 249 differentially expressed genes (DEGs) between the SA treatment and CK group. Up-regulation of three DEGs (BMY1, BMY2, and AMY) related to the starch and sucrose metabolism pathway accelerated the oxidative decomposition of sugar to release energy for biosynthesis. Two up-regulated (PetF and Lhcb1) and two down-regulated (Lhcb2-1 and Lhcb2-2) genes involved in the photosynthesis pathway may contribute to TTL biosynthesis. SA-regulated genes may alter antioxidant enzyme activity and endogenous hormone content levels to facilitate TTL biosynthesis. Among these DEGs, candidate structural genes (HMGR, CYP450, CPR, and TPS) and transcription factors (MYB and WRKY) played key roles in SA-promoted TTL accumulation in G. biloba. Quantitative real-time PCR analysis verified the expression patterns of all of the selected DEGs. The results provide novel insights into the transcriptional regulatory mechanism of the promotive effect of SA on TTL biosynthesis in G. biloba.