Effect of solid-medium coupled with reactive oxygen species on ganoderic acid biosynthesis and MAP kinase phosphorylation in Ganoderma lucidum

Abstract

Ganoderma lucidum is used as a functional food and medicinal mushroom in Asia. Biosynthesis of its active ingredients, the ganoderic acids (GAs), together with signal transduction related to the fungal biology of G. lucidum, are critical for this application. However, regulation of G. lucidum GA biosynthesis and signal transduction remains enigmatic. We investigated the role of reactive oxygen species (ROS) on biosynthesis of individual GAs and on MAPK (mitogen-activated protein kinase) signaling. Antioxidant treatment decreased lanosta-7,9(11), 24-trien-3α-01-26-oic acid (ganoderic acid 24) and total GA production. Cultures incubated with the pro-oxidant CDNB (1-chloro-2,4-dinitrobenzene) or H2O2, increased production of ganoderic acid 24 and total GAs were found. Interestingly, CDNB reduced RNA expression of the squalene synthase and lanosterol synthase, indicating that both genes may not be bottlenecks in GA induction. H2O2 induced phosphorylation of the proteins Hog-1 and Fus3, which are homologs of the mammalian MAPKs p38 and ERK (extracellular signal-related kinases), respectively. CDNB also enhanced phosphorylation of Hog1 but had no effect on Fus3. To the best of our knowledge, this is the first report indicating that ROS regulate the biosynthesis of individual GAs and affect MAPK signaling in G. lucidum. This study also identifies the potential application of ROS to the G. lucidum functional food industry.