Background

Ganoderma lucidum(Leyss.ex.Fr)Karst.，Ling-Zhi in Chinese and Reishi in Japanese，belonging to the Ganodermataceae of Aphyllophorales in Basidiomycetes［1］，is a widely distributed fungus in the tropic and subtropics of Asia，Africa and America［2］，with the most diversities in China.G.lucidum is one of the most famous Traditional Chinese Medicine and is widely used as a tonic for longevity and overall health in China for thousands of years［3］.G.lucidum has been proved with remarkable pharmacological activities and therapeutic effects in immuno-modulating，anti-cancer，anti-radiation and detoxification for various human diseases［4- 7］.However，the accumulation of its active ingredients and the pharmacological mechanisms are mainly unknown.The genome sequence and gene annotation of G.lucidum will provide key resources and may speed up the function research of G.lucidum to human health.

Ganoderic acid(GA)，one of the main active ingredients of G.lucidum，is a kind of triterpenoid secondary metabolites and shows the ability to participate in many biological activities including antitumor and antioxidant etc［8］.However，the content of GAs is very low and GAs are suggested to be the quality indicator of G.lucidum in Japan［1，9］.It is suggested that GAs could be biosynthesized via the mevalonic acid(MVA)pathway.Several genes in this pathway have been cloned in G.lucidum，including 3-Hydroxy-3-methylglutaryl-Co A reductase(HMGR)［10］，Farnesyl diphosphate synthase(FPPs)［11］，Squalene synthase(SQS)［12］，and Lanosterol synthase(also namely 2，3-oxidosqualene lanosterol cyclase，OSC)［13］.However，it is known very limited about the processes of decoration after the triterpene backbone biosynthesis，such as cyclization and glycosylation，which are very important for GAs synthesis，and even the synthases.The genome sequence is expected to characterize the enzymes of these key steps in the GAs biosynthesis.

G.lucidum is one of the white-rot fungi that could grow on the dead trees by degrading cellulose，hemicellulose and lignin.Lignin，one of the main polymeric components of plant cell wall，is highly resistant to chemical and biological degradation［14］.As one of the dominant organisms decomposing lignocellulose，G.lucidum may play an important role in renewable energy production.Although there are some studies about the ligninolytic enzymes，the mechanism of lignin degradation is still not fully understood［14- 16］.In addition，different enzymatic systems are employed in different fungi［17］.The enzymatic system and genes about wood degradation in G.lucidum are unknown.(https://www.daowen.com)

With the development of next-generation DNA sequencing，several macrofungi have been sequenced and analyzed to illuminate different aspects.Ohm et al.［18］studied the fruiting bodies formation and lignocelluloses degradation of Schizophyllum commune.Stajich et al.［19］completed the chromosome assembly of Coprinopsis cinerea，and investigated the rates of meiotic recombination and the distribution，expression，evolutionary conservation of single-copy genes and gene families.Martin et al.illustrated the different ways of genetic predisposition for symbiosis in basidiomycete Laccaria bicolor［20］and ascomycete Tubermelanosporum Vittad［21］.The genome annotation of G.lucidum will provide important data to further function and mechanism research in G.lucidum and comparative genomics.

In this study，we report the genomic sequence of the monokaryotic G.lucidum strain.The genome was assembled into 39.9 megabases(Mb).With the genome sequences and gene annotation，we illuminate the synthesis of GAs as a model system to study triterpenoid biosynthesis in fungi.Besides the importance of understanding the biosynthesis of this important active ingredient，insight into the enzyme system of lignocelluloses degradation in G.lucidum may speed up the process of understanding the lignocelluloses degradation mechanism for industrial applications.