Role of nitric oxide and hydrogen peroxide in artemisinin increase of Artemisia annua L. hairy roots induced by an oligosaccharide elicitor from endophytic Fusarium sp. SZ1

Artemisia annua L. is presently the sole natural source of antimalarial drug artemisinin. Endophytic fungi, which spend their entire life spans inside the healthy A. annua plant, exhibit intimate impact on the growth and physiology of their hosts. An oligosaccharide elicitor (OE) of one endophytic fungi (Fusarium sp. SZ1) induced multiple responses in A. annua hairy roots, including rapid generation of nitric oxide (NO) and reactive oxygen species (ROS), sequentially followed by enhancement of artemisinin production. The purpose of this work was to characterise NO and ROS and their relationships with the induced artemisinin. The OE at 0.3mg total sugar/mL induced a rapid nitric oxide synthase (NOS)-dependent NO and H₂O₂ production in the cultures, which exhibited a biphasic time course, reaching the first plateau within 1.5h and the second within 8h after the elicitation. The NO donor sodium nitroprusside (SNP) potentiated OE-induced H₂O₂ production and OE-induced NO was suppressed by NADPH oxidase inhibitor diphenylene iodonium (DPI) and a scavenger of H₂O₂, catalase (CAT). The inhibition of NOS activity by DPI and CAT, NADPH oxidase activity by NOS inhibitor and NO scavenger show that the OE-induced NO production and H₂O₂ production are interdependent. Moreover, the OE-induced NO and ROS were involved in stimulating the bioconversion from artemisinic acid to artemisinin. These results suggest that the mutual effects between NO and ROS play a signal role in the elicitor-induced responses and secondary metabolism activities in Artemisia annua L.

Acknowledgements: Supported by the National Natural Science Foundation of China (30772731)