De Novo Transcriptome Sequencing of the Deep-Sea-Derived Fungus Dichotomomyces cejpii and Analysis of Gliotoxin Biosynthesis Genes

Gliotoxin, produced by fungi, is an epipolythiodioxopiperazine (ETP) toxin with bioactivities such as anti-liver fibrosis, antitumor, antifungus, antivirus, antioxidation, and immunoregulation. Recently, cytotoxic gliotoxins were isolated from a deep-sea-derived fungus, Dichotomomyces cejpii. However, the biosynthetic pathway for gliotoxins in D. cejpii remains unclear. In this study, the transcriptome of D. cejpii was sequenced using an Illumina Hiseq 2000. A total of 19,125 unigenes for D. cejpii were obtained from 9.73 GB of clean reads. Ten genes related to gliotoxin biosynthesis were annotated. The expression levels of gliotoxin-related genes were detected through quantitative real-time polymerase chain reaction (qRT-PCR). The GliG gene, encoding a glutathione S-transferase (DC-GST); GliI, encoding an aminotransferase (DC-AI); and GliO, encoding an aldehyde reductase (DC-AR), were cloned and expressed, purified, and characterized. The results suggested the important roles of DC-GST, DC-AT, and DC-AR in the biosynthesis of gliotoxins. Our study on the genes related to gliotoxin biosynthesis establishes a molecular foundation for the wider application of gliotoxins from D. cejpii in the biomedical industry in the future.