Involvement of nitric oxide in oxidative burst, phenylalanine ammonia-lyase activation and Taxol production induced by low-energy ultrasound in Taxus yunnanensis cell suspension cultures

Abstract: This work was to characterize the generation of nitric oxide (NO) in Taxus yunnanensis cells exposed to low-energy ultrasound (US) and the signal role of NO in elicitation of plant defense responses and secondary metabolite accumulation. The US sonication (3.5–55.6mW/cm3 at 40kHz fixed frequency) for 2min induced a rapid and dose-dependent NO production in the Taxus cell culture, which exhibited a biphasic time course, reaching the first plateau within 1.5h and the second within 7h after US sonication. The NO donor sodium nitroprusside (SNP) potentiated US-induced H2O2 production and cell death. Inhibition of nitric oxide synthase (NOS) activity by N ω -nitro-l-arginine (l-NNA) or scavenging NO by 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxyde (PTIO) partially blocked the US-induced H2O2 production and cell death. Moreover, the NO inhibitors suppressed US-induced activation of phenylalanine ammonium-lyase (PAL) and accumulation of diterpenoid taxanes (Taxol and baccatin III). These results suggest that NO plays a signal role in the US-induced responses and secondary metabolism activities in the Taxus cells. [Copyright &y& Elsevier]