Abscisic acid-mediated cytosolic Ca2+ modulates triterpenoid accumulation of Ganoderma lucidum.

Abstract

Ganoderma lucidum is a mushroom widely used for its edible and medicinal properties. Primary bioactive constituents of G. lucidum are ganoderic triterpenoids (GTs), which exhibit important pharmacological activity. Abscisic acid (ABA), a plant hormone, is associated with plant growth, development, and stress responses. ABA can also affect the growth, metabolism, and physiological activities of different fungi and participates in the regulation of the tetracyclic triterpenes of some plants. Our findings indicated that ABA treatment promoted GT accumulation by regulating the gene expression levels (squalene synthase (sqs), 3-hydroxy-3-methylglutaryl-CoA reductase (hmgr), and lanosterol synthase (ls)), and also activated cytosolic Ca2+ channels. Furthermore, under ABA mediation, exogenous Ca2+ donors and inhibitors directly affected the cytosolic Ca2+ concentration and related gene expression in Ca2+ signaling. Our study also revealed that ABA-mediated cytosolic Ca2+ played a crucial regulatory role in GT biosynthesis, accompanied by antioxidant defense modulation with increasing superoxide dismutase (SOD) activity and ascorbate peroxidase (APX) activity, and the resistance ability of O2•- and glutathione (GSH) contents.