Nitric oxide potentiates oligosaccharide-induced artemisinin production in Artemisia annua hairy roots

The purpose of the present study was to characterize the generation of nitric oxide ( NO) in Artemisia annua roots induced by an oligosaccharide elicitor (OE) from Fusarium oxysporum mycelium and the potentiation role of NO in the elicitation of artemisinin accumulation. The OE (0.3mg total sugar/mL) induced a rapid production of NO in cultures, which exhibited a biphasic time course, reaching the first plateau within 1.5 h and the second within 8 h of OE treatment. Artemisinin content in 20-day-old hairy roots was increased from 0.7mg/g dry wt to 1.3mg/g dry wt by using the OE treatment for 4 d. In the absence of OE, the NO donor sodium nitroprusside (SNP) at 10, 50 mu M and 100 mu M enhanced the growth of hairy roots, but had no effect on artemisinin synthesis. The combination of SNP with OE increased artemisinin content from 1.2 mg/g drywt to 2.2mg/g dry wt, whereas the maximum production of artemisinin in cultures was 28.5mg/L, a twofold increase over the OE treatment alone. The effects of SNP on the OE-induced artemisinin were suppressed strongly by the NO scavenger 2-(4-carboxyphenyl)- 4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO). The results suggest that NO can strongly potentiate elicitor-induced artemisinin synthesis in A. annua hairy roots.