Research progress on ustiloxins and its biosynthetic pathway

Ustiloxins is a kind of cyclic peptide mycotoxin produced by Ustilaginoidea virens. Rice false smut (RFS), caused by U. virens, significantly increases the rate of empty bast, reduces grain weight, and ultimately affects the rice yield. Additionally, ustiloxins, produced by U. virens, change the rice quality and seriously threaten food safety in China. In recent years, with the development of genomics and molecular biology, the biosynthetic pathway of ustiloxins and its regulatory mechanism have been studied in depth. At present, the biosynthetic pathway of ustiloxins B is the clearest and it is mainly concentrated in Aspergillus flavus. There are 11 genes involved in the biosynthetic pathway of ustiloxins B, which are not only regulated by gene transcription level, but also by pathway-specific regulator ustR, protease kexB and global regulator LaeA. In this review, novel structures, physicochemical properties of the ustiloxins and their detection methods were summarized, with emphasis on the biosynthetic pathway of ustiloxins and its regulatory mechanism, which will lay a foundation for further research on the biosynthesis pathways and regulatory mechanisms of ustiloxins in Aspergillus flavus.