Exploring The Sclerotium Formation Mechanism Of Poria Cocos(Schw.) Wolf By Genomic And Transcriptomic Analysis

Many fungi form persistent and dormant sclerotia with compact hardened mycelium during unfavorable circumstances.While most of these sclerotia are small in size,Wolfiporia cocos grows into a giant sclerotium,which is widely used as a traditional medicine in Asian countries.We sequenced and assembled the genome of a cultivated W.cocos strain(WCLT).The 62 Mb haploid genome contains 44.2% repeat sequences,of which,48.0% are transposable elements(TEs).Contrary to the genome of W.cocos from North America,WCLT has independently undergone a whole genome duplication(WGD)event.The TEs and WGD occurrence overlapped an archaeological pleistocene stage with low oxygen and high temperature and these stresses might have induced sclerotium differences due to geographical distribution.A few wood decomposition enzymes were absent from WCLT but present in other fungi close in the phylogeny;while some others exhibited higher expression in sclerotium,which might allow the mushroom to absorb sufficient nutrients for robust growth,whilst it keeps generating stress signals for sclerotium development.The key genes for triterpene biosynthesis are expressed highest in the sclerotium epidermis,which affects the enrichment of triterpenoids in the epidermis.In addition,CYP5027B10(WC08328),CYP5027B11(WC08329)and CYP5354A(WC04233)genes are most likely to play a role in the modification and synthesis of certain triterpenoids.The NAD-related families,reverse transcriptases,zinc finger transcription factors and protein kinase C families have significant numbers expansion.Combined with transcriptome expression analysis,paralogous sclerotium-regulator kinase,aquaporins,PHA03247 superfamily,GAL4,SLC5-6-like＿sbd and highly expanded gene families in WCLT genome jointly regulate the sclerotium formation and swelling.