Nano-selenium promotes the product quality and plant defense of Salvia miltiorrhiza by inducing tanshinones and salvianolic acids accumulation

Selenium (Se) is a non-essential element for plants, but it has dosage effects on plant's life in some environments. Although many studies have revealed the beneficial effects of Se on the plant growth and defense of grains, fruits and vegetables, the underlying mechanism is largely unknown. Here, the effects of nanoparticle Se (Nano-Se) on Salvia miltiorrhiza, a valuable traditional Chinese medicine, were described. Ten mg/L Nano-Se was the optimum concentration for foliar application to stimulate plant growth, antioxidant capacity, and the accumulation of tanshinones and salvianolic acids. With the increase in the duration of Nano-Se exposure, plant biomass, nutrients and tanshinones contents gradually increased, while the salvianolic acids contents first increased significantly and then decreased. Transcriptomic analysis showed that the promotion effects of Nano-Se were probably due to the activation of photosynthesis, plant hormone signal transduction and antioxidant response in S. miltiorrhiza. Nano-Se might increase the contents of tanshinones and salvianolic acids by activating the salicylic acid (SA) and jasmonic acid (JA) signaling pathways and the downstream APETALA2/ethylene-responsive element binding factors (AP2/ERF) and WRKY transcription factors. Insect bioassays revealed that Nano-Se could reduce the survival and fecundity of aphids on S. miltiorrhiza by inducing the contents of salvianolic acid B (SalB) and rosmarinic acid (RA). Thus, these results indicate that Nano-Se could promote the crop yield, product quality and pest resistance of S. miltiorrhiza by inducing plant biomass and secondary metabolites. Our study suggests potential applications of Nano-Se in the production of industry crops.