Genome Sequencing of Inonotus Obliquus Reveals Insights Into Candidate Genes Involved In Secondary Metabolite Biosynthesis

Abstract

Background: Inonotus obliquus is an important edible and medicinal mushroom that was shown to have many pharmacological activities in preclinical trials, including anti-inflammatory, antitumor, immunomodulatory, and antioxidant effects. However, the biosynthesis of these pharmacological components has rarely been reported. The reason for this is that there have been no relevant reports on its genome information.Results: we report the genome of I. obliquus using a combined high-throughput Illumina NovaSeq with Oxford Nanopore PromethION sequencing platform. The de novo assembled 38.18 Mb I. obliquus genome was determined to harbor 12525 putative genes, with 81.83% of them having detectable sequence similarities to others available in public databases. Phylogenetic analysis revealed a close evolutionary relationship between I. obliquus and Fomitiporia mediterranea and Sanghuangporus baumii in the core Hymenochaetales clade. The I. obliquus genome was found to encode a repertoire of enzymes involved in carbohydrate metabolism, along with 135 cytochrome P450 proteins. Other annotated genes included those encoding key enzymes for secondary metabolite biosynthesis, such as those from polysaccharide, melanin, and triterpenoid pathways. Among them, the I. obliquus genome was particularly enriched in sesquiterpenoid biosynthesis genes and gene clusters.Conclusions: This study presents the first genome analysis of an important medical mushroom, I. obliquus, which can provide insights into the usefulness of this organism and its secondary metabolites in medicine.