Induced effect of Na⁺ on ganoderic acid biosynthesis in static liquid culture of Ganoderma lucidum via calcineurin signal transduction

Abstract

Na(+)/Ca(2+) exchange is important to cell physiology and metabolism, but its role in the secondary metabolite biosynthesis by fungi is yet unclear. In this work, in static liquid cultures of Ganoderma lucidum, which is an efficient process for hyper-production of anti-tumor ganoderic acids (GAs), it was interestingly found that Na(+) addition could enhance the GAs production, but K(+) did not. Further investigation by intracellular Ca(2+) imaging and using a calcineurin inhibitor (i.e., cyclosporin A) revealed that addition of Na(+) led to the influx of Ca(2+) from culture broth to the cells and calcineurin signals were also triggered. Addition of 100 mM Na(+) at the beginning of the static liquid cultivation, in which the addition dosage and timing were optimized, resulted in 2.8-fold improvement of total GAs production. Quantitative gene transcription analysis indicated that the expression levels of the genes of Ca(2+) sensors and GA biosynthesis were upregulated with Na(+) induction while downregulated by using the calcineurin inhibitor, implying that higher GA production might result from higher expression of those genes. This work not only provided a simple and efficient induction strategy by Na(+) addition for the improved GAs production but also suggested the regulation mechanism of Na(+) on the GA biosynthesis through calcineurin signaling transduction.

From 2000years of Ganoderma lucidum to recent developments in nutraceuticals

“…It was found that the addition of sodium and manganese can lead to a 2.8 and a 2.2-fold increase in the GA content, respectively (Xu et al, 2013(Xu et al, , 2014. The increased GA production is likely due to the activation of calcineurin signalling pathway induced by calcium/sodium exchange (Xu et al, 2013;. Furthermore, production of GAs can be improved by deliberate overexpression of specific genes in G. lucidum .…”

“…By manipulating the fermentation conditions such as medium components, oxygen supply, and pH, the production of GAs in the mycelium can be enhanced. It was found that the addition of sodium and manganese can lead to a 2.8 and a 2.2-fold increase in the GA content, respectively (Xu et al, 2013(Xu et al, , 2014. The increased GA production is likely due to the activation of calcineurin signalling pathway induced by calcium/sodium exchange (Xu et al, 2013;.…”

Induction of apoptosis and ganoderic acid biosynthesis by cAMP signaling in Ganoderma lucidum

“…The expression of SQS, LS, and HMGR was enhanced in static liquid culture as compared with shaking culture 48 . Sodium, methyl jasmonate, phenobarbital, and acetic acid induced GA production and increased the expression of GA biosynthetic genes 26, 49–51 . However, our data showed that NaF, caffeine, and cAMP induced GA production but reduced the gene expression of SQS and LS.…”

“…and our lab have demonstrated that ROS and Ca 2+ are able to regulate GA biosynthesis 18, 24, 25 . Sodium and manganese have been shown to trigger Ca 2+ signaling, which, in turn, leads to an enhancement of GA production 26, 27 . Recently, Mu et al .…”

Ganoderic Acid and Lucidenic Acid (Triterpenoid)

“…Other biologically active compounds (such as sterols, polysaccharides, and glycoproteins) have also been isolated from these mushrooms and possessed pharmacological activities including cytotoxic, antiviral, anti-inflammatory, hypoglycemic, and immunostimulant activities [33][34][35][36][37]. Optimization of the fermentation process (including Ganoderma strain screening and optimization of the fermentation process conditions) plays an important role in improving the production of triterpenoids [43][44][45][46][47][48][49][50][51]. Moreover, the content of triterpenoids isolated from fruit body of Ganoderma species is too low and very expensive.…”