Enhancement of Ganoderic Acid Accumulation by Overexpression of an N-Terminally Truncated 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Gene in the Basidiomycete Ganoderma lucidum

Abstract

ABSTRACTGanoderic acids produced byGanoderma lucidum, a well-known traditional Chinese medicinal mushroom, exhibit antitumor and antimetastasis activities. Genetic modification ofG. lucidumis difficult but critical for the enhancement of cellular accumulation of ganoderic acids. In this study, a homologous genetic transformation system forG. lucidumwas developed for the first time using mutatedsdhB, encoding the iron-sulfur protein subunit of succinate dehydrogenase, as a selection marker. The truncatedG. lucidumgene encoding the catalytic domain of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) was overexpressed by using theAgrobacterium tumefaciens-mediated transformation system. The results showed that the mutatedsdhBsuccessfully conferred carboxin resistance upon transformation. Most of the integrated transfer DNA (T-DNA) appeared as a single copy in the genome. Moreover, deregulated constitutive overexpression of the HMGR gene led to a 2-fold increase in ganoderic acid content. It also increased the accumulation of intermediates (squalene and lanosterol) and the upregulation of downstream genes such as those of farnesyl pyrophosphate synthase, squalene synthase, and lanosterol synthase. This study demonstrates that transgenic basidiomyceteG. lucidumis a promising system to achieve metabolic engineering of the ganoderic acid pathway.