Physiological Response and Transcriptome Profiling Reveal Phosphate-Mediated Amelioration of Arsenic Accumulation and Toxicity in Panax Notoginseng

Panax notoginseng is an important medical plant and is widely used in clinical treatment in China. However, the arsenic (As) contamination in taproots of P. notoginseng has not been effectively solved in main planting areas that would be a big threat to the persons who used. Mechanisms of response and resistance of P. notoginseng to As were revealed by determining physiological parameters and transcriptome profiling of roots in the presenting study. Phosphate-mediated amelioration of As accumulation in P. notoginseng was also investigated. Results showed that the biomass and notoginsenoside contents of P. notoginseng sharply decreased under As exposure or phosphorus (P) deficiency, but the addition of phosphate (Pi) ameliorated this reduction. Notably, As acquisition and translocation were weakened by supplementation with Pi. The antioxidant defense system of P. notoginseng was strengthened by the enhanced activities of antioxidases and elevated antioxidant contents under As exposure and Pi deficiency, e.g., superoxide dismutase (SOD), peroxidase (POD), malondialdehyde (MDA) and glutathione (GSH). Transcriptome analysis revealed that differentially expressed genes (DEGs) of P. notoginseng involved in saponin biosynthesis were mainly clustered into the CYP450 and UGT families under interactive treatment with Pi and As(V). Genes of Pi transporters (Phts), GSHs, phytochelatins (Pcs) and arsenate reductase (AR) were involved in As accumulation and detoxification in P. notoginseng. Taken together, supplying Pi-fertilizer is potentially an effective strategy for reducing As acquisition and accumulation but increasing saponin production in P. notoginseng.