Signal transduction and metabolic flux of β-thujaplicin and monoterpene biosynthesis in elicited Cupressus lusitanica cell cultures

Abstract

β-Thujaplicin is an antimicrobial tropolone derived from geranyl pyrophosphate(GPP) and monoterpene intermediate. Yeast elicitor-treated Cupressus lusitanica cell cultures accumulate high levels of β-thujaplicin at early stages and other monoterpenes at later stages post-elicitation. The different regulation of β-thujaplicin and monoterpene biosynthesis and signal transduction directing metabolic flux to β-thujaplicin firstly and then shifting metabolic flow from β-thujaplicin to other monoterpene biosynthesis were investigated. The earlier rapid induction of β-thujaplicin accumulation and a later stimulation of monoterpene biosynthesis by yeast elicitor are in well agreement with elicitor-induced changes in activity of three monoterpene biosynthetic enzymes including isopentenyl pyrophosphate isomerase, GPP synthase, and monoterpene synthase. Yeast elicitor induces an earlier and stronger β-thujaplicin production and monoterpene biosynthetic enzyme activity than methyl jasmonate (MeJA) does. Profiling all monoterpenes produced by C. lusitanica cell cultures under different conditions reveals that β-thujaplicin biosynthesis parallels with other monoterpenes and competes for common precursor pools. Yet β-thujaplicin is produced pre-dominantly at early stage of elicitation whereas other monoterpenes are mainly accumulated at late stage while β-thujaplicin is metabolized. It is suggested that yeast elicitor-treated C. lusitanica cells preferentially accumulate β-thujaplicin as a primary defense and other monoterpenes as a secondary defense. Inhibitor treatments suggest that immediate production of β-thujaplicin post-elicitation largely depends on pre-existing enzymes and translation of pre-existing transcripts as well as recruitment of precursor pools from both the cytosol and plastids. The later β-thujaplicin and other monoterpene accumulation strictly depends on active transcription and translation. Induction of β-thujaplicin production and activation of monoterpene biosynthetic enzymes by elicitor involves similar signaling pathways, which may activate early β-thujaplicin production and later monoterpene biosynthesis and induce a metabolic flux shift from β-thujaplicin to monoterpene accumulation.