Role of tri18 gene in Epiroridin E production and toxin resistance mechanisms in Paramyrothecium roridum.

Type D trichothecene toxins represent a class of macrocyclic trichothecene toxins with significant cytotoxicities towards human and crops. These toxins can also be used as anti-tumor compounds by the combination of antibody-drug conjugate. Therefore, it is urgent to investigate the biosynthetic routine of type D trichothecene toxins and explore type D trichothecene toxin-resistant genes, in order to ameliorate the hazard of trichothecene toxins and to facilitate the heterologous expression of toxin-biosynthetic cluster. In this study, tri18 gene was firstly knocked out in Paramyrothecium roridum, leading to the complete absence of type D trichothecene toxin epiroridin E, which can be restored by the complement of tri18 gene. Additionally, the knockout of tri18 gene led to a significant reduction in the pathogenicity of P. roridum towards pumpkin. Meanwhile, the enzymatic properties of Tri18 protein towards trichothecene deoxynivalenol (DON) toxin were also characterized. Moreover, tri3 and tri17KR with broad spectrum toxin-resistance function within the tri cluster were initially discovered through heterologous expression in toxin-sensitive Saccharomyces cerevisiae. And this study provides innovative type D trichothecene toxin resistant enzymes, which can provides green platform for the production of type D trichothecene toxins, thus promoting the application of these toxins in biomedical field.

The excavation of novel toxin-resistance proteins against trichothecenes toxins in Paramyrothecium roridum.

Trichothecene toxins cause serious hazard towards human health and economical crops. However, there are no sufficient molecular strategies to reduce the hazard of trichothecene toxins. Thus it is urgent to exploit novel approaches to control the hazard of trichothecenes. In this study, four trichothecene toxin-resistance genes including mfs1, GNAT1, TRP1 and tri12 in Paramyrothecium roridum were excavated based on genome sequencing results, and then expressed in toxin-sensitive Saccharomyces cerevisiae BJ5464, the toxin resistance genes pdr5, pdr10 and pdr15 of which were firstly knocked out simultaneously by the introduction of TAA stop codon employing CRISPR/Cas9 system. Therefore, three novel hazardous toxin-resistance genes mfs1, GNAT1, TRP1 in P. roridum were firstly excavated by the co-incubation of DON toxin and toxin resistant genes-containing BJ5464 strains. The in vitro function and properties of novel toxin-resistance genes coding proteins including GNAT1, MFS1 and TRP1 were identified by heterologous expression and cellular location analysis as well as in vitro biochemical reaction. The excavation of novel trichothecene toxin-resistance genes provide novel molecular clues for controlling the harm of trichothecenes, meanwhile, this study will also pave a new way for the yield improvement of trichothecenes by heterologous expression to facilitate the development of trichothecenes as anti-tumor lead compounds.

Recent Advances on Macrocyclic Trichothecenes, Their Bioactivities and Biosynthetic Pathway.

Macrocyclic trichothecenes are an important group of trichothecenes bearing a large ring. Despite the fact that many of trichothecenes are of concern in agriculture, food contamination, health care and building protection, the macrocyclic ones are becoming the research hotspot because of their diversity in structure and biologic activity. Several researchers have declared that macrocyclic trichothecenes have great potential to be developed as antitumor agents, due to the plenty of their compounds and bioactivities. In this review we summarize the newly discovered macrocyclic trichothecenes and their bioactivities over the last decade, as well as identifications of genes tri17 and tri18 involved in the trichothecene biosynthesis and putative biosynthetic pathway. According to the search results in database and phylogenetic trees generated in the review, the species of the genera Podostroma and Monosporascus would probably be great sources for producing macrocyclic trichothecenes. Moreover, we propose that the macrocyclic trichothecene roridin E could be formed via acylation or esterification of the long side chain linked with C-4 to the hydroxyl group at C-15, and vice versa. More assays and evidences are needed to support this hypothesis, which would promote the verification of the proposed pathway.