Effects of Exogenous Elicitors on Triterpenoids Accumulation and Expression of Farnesyl Diphosphate Synthase Gene in Inonotus obliquus

Abstract

Exogenous elicitors can influence accumulation of triterpenoids by regulating FPS (farnesyl pyrophosphate synthase) in Inonotus obliquus, such as birch bark (BB), birch rhizosphere soil (BS), Frankia alni (FA), and Rhizobium indigoferae (RI). Among them, the highest yield of biomass (15.6 mg/mL) could be detected by treatment with RI at 2 µg/mL for 10 d, about 2.1-fold of the control. Results showed the significant effect of elicitors on accumulation of triterpenoids by regulating FPS expression level. RI stimulated mycelium to achieve the highest accumulation of triterpenoids about 48.2 mg/g, which was about over 4-fold of the control (9.5 mg/g). Its effect on FPS expression level was greater than that of others, which was about over 10-fold of the control. However, accumulation of triterpenoids and FPS expression level were clearly down-regulated under treatment with BS. In addition, two endogenous factors (H2O2 and NO) in I. obliquus could affect accumulation of triterpenoids by regulating FPS expression level. Effect of RI on H2O2 and NO contents were higher than that of others, about 3.5-fold of the control. The minimum value of H2O2 content was detected by treatment with BS for 10 d, which was about 0.5-fold of the control. RI that assist with CAT (catalase) and SNP (sodium nitroprusside dehydrate) could stimulate triterpenoid contents to achieve highest accumulation, which was about 5.5-fold of the control. Fluctuation of H2O2 and NO content seems to play a pivotal role in accumulation of triterpenoids by regulating FPS expression level.