Naturally-produced beauvericins and divergence of BEAS gene among Fusarium and Trichoderma species

Beauvericin (BEA) and its analogs are non-ribosomal cyclodepsipeptide mycotoxins produced by a wide range of fungal species, including saprotrophs, plant, and insect pathogens, particularly belonging to Fusarium, Trichoderma, Beauveria, and Isaria genera. Most beauvericin analogs were described among Beauveria and Isaria genera as “unnatural” beauvericins by adding amino acid precursors to the growing media. The aim of the study was to find BEAs naturally-synthesized by Fusarium species and tentatively determine their structures using mass spectrometry. Moreover, because of the unknown ability to produce beauvericin by Trichoderma fungi, we carried out the quantitative analysis using UPLC-MS. We also analyzed the polymorphism of the BEAS gene by sequencing partial BEAS regions from Trichoderma and Fusarium species.

We screened five fungal cultures from the Fusarium genus cultivated on rice grain for the presence of the new natural beauvericins. The peptide sequence data of beauvericin analogs were established using MS/MS experiments as well as amino acid and hydroxy acid analysis following acid hydrolysis. Ten cyclodepsipeptide analogs described earlier were tentatively identified in the extract. In addition, two so far undescribed tyrosine-containing beauvericin analogs were tentatively identified in the cultures. Moreover, a quantitative analysis of beauvericin was performed using a UPLC-MS in eleven Trichoderma and six Fusarium rice cultures. The phylogenic analyses of beauvericin synthase (BEAS) divergence were performed on the basis of sequenced PCR-amplified fragments from Trichoderma and Fusarium fungi and partial reference genes from the GenBank database (representing Beauveria, Fusarium, and Trichoderma genera).

This study demonstrates the high variability of naturally-produced new types of beauvericins, such as tyrosine-containing analogs in Fusarium fungi. It also shows that fungi belonging to the Trichoderma genus possess the ability to produce beauvericin.