Physiological and transcriptomic analyses of roots from Panax ginseng C. A. Meyer under drought stress

Drought is one of the main limiting factors that strongly affects the growth, development and secondary metabolic processes of plants. Panax ginseng C. A. Meyer is an essential source of pharmaceuticals, and ginsenosides are the main active ingredients. Studies on the response to drought stress on the physiological and molecular mechanism regulation of ginseng are scarce. Therefore, we evaluated the root biomass, ginsenoside content, and physiological and transcriptional responses of ginseng under drought stress. We found that drought stress hindered the increase in ginseng root biomass but promoted ginsenoside accumulation. The physiological results showed that drought stress increased the content of malondialdehyde (MDA), osmoregulatory substances, and abscisic acid (ABA), also enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in ginseng roots. In addition, the transcriptome results revealed that many differentially expressed genes (DEGs) were enriched in the plant hormone signal transduction pathway, twelve DEGs from the ABA signaling pathway were identified as key mediators of the drought stress response. Moreover, twenty-six key enzyme genes involved in the ginsenoside synthesis pathway were identified, seven of these genes might be considered key regulators of ginsenoside biosynthesis in response to drought stress in ginseng. This study contributes to an improved understanding of the mechanism by which drought stress regulates ginsenoside biosynthesis in ginseng.