Cloning and functional characterization of sesquiterpene synthase genes from Inonotus obliquus using a Saccharomyces cerevisiae expression system.

Inonotus obliquus (Chaga mushroom) is a large medicinal and edible fungus that contains a wealth of bioactive terpenoids. However, the detection of certain low-abundance sesquiterpenoids remains a challenge due to limitations in extraction and analytical techniques. Furthermore, the synthase genes responsible for the biosynthesis of the identified terpenoids have not yet been clearly elucidated. To address this, our study combined transcriptome mining with yeast heterologous expression to investigate the synthase genes involved in sesquiterpenoid production in I. obliquus. We successfully identified eight sesquiterpene synthase genes and one farnesyltransferase. Among these, only cis-β-farnesene, synthesized by IoTPS2, had been previously detected before in the sclerotium of I. obliquus, while the other nine sesquiterpenoids-including neoisolongifolene-8-ol, β-longipinene, vetiselinenol, isolongifolene, 7,8-dehydro-8a-hydroxy-, 4a,8b,10b,11a-tetramethylbicyclo[6.3.0]undec-1-en-5-one, 6,11-oxido-acor-4-ene, β-maaliene, neointermedeol, and longifolenaldehyde-were discovered for the first time. This research provides a critical scientific foundation for expanding the known repertoire of sesquiterpenoids and their corresponding synthase genes in I. obliquus.