Endogenous hydrogen peroxide is a key factor in the yeast extract-induced activation of biphenyl biosynthesis in cell cultures of Sorbus aucuparia

摘要

Biphenyls are unique phytoalexins produced by plants belonging to Pyrinae, a subtribe of the economically important Rosaceae family. The formation of aucuparin, a well-known biphenyl, is induced by yeast extract (YE) in cell cultures of Sorbus aucuparia. However, the molecular mechanism underlying YE-induced activation of biphenyl biosynthesis remains unknown. Here we demonstrate that the addition of YE to the cell cultures results in a burst of reactive oxygen species (ROS; H2O2 and O2 −), followed by transcriptional activation of the biphenyl synthase 1 gene (BIS1) encoding the key enzyme of the biphenyl biosynthetic pathway and aucuparin accumulation. Pretreatment of the cell cultures with ROS scavenger dihydrolipoic acid and NADPH oxidase-specific inhibitor diphenylene iodonium abolished all of the above YE-induced biological events. However, when the cell cultures was pretreated with superoxide dismutase specific inhibitor N,N-diethyldithiocarbamic acid, although O2 − continued to be generated, the H2O2 accumulation, BIS1 expression and aucuparin production were blocked. Interestingly, exogenous supply of H2O2 in the range of 0.05–10 mM failed to induce aucuparin accumulation. These results indicate that endogenous generation of H2O2 rather than that of O2 − is a key factor in YE-induced accumulation of biphenyl phytoalexins in cell cultures of S. aucuparia.