Objective

Swainsonine (SW) is the principal toxic ingredient of locoweeds, and is produced by multiple fungi. A key enzyme in the SW synthesis pathway is a hybrid swnk/nrps. To analyze the role of swnk in the SW biosynthesis pathway of Metarhizium anisopliae.

Results

The concentration of SW and the swnk expression in M. anisopliae fermentation from 1st to 7th day were determined using LC–MS and RT-qPCR, respectively. M. anisopliae had the highest SW content and swnk expression on the 5th day of fermentation; Mutant strain (MT) were obtained by PEG-mediated homologous recombination (HR) which knocked out swnk in the wild-type (WT) strain. Complemented-type (CT) strain were obtained by transforming a modified PUC19 complementation vector containing the geneticin (G418) resistance gene and swnK. SW was not detected in the MT strain and reverted to its original level in the CT strain; A Psilent-1 plasmid with Benomyl (ben)-resistant that was used interfered with swnk of WT strain. The level of SW was markedly diminished in the RNAi strain. RNAi of swnk affects the formation of the cell wall in M. anisopliae.

Conclusion

These results indicate that swnk plays a crucial role in the SW biosynthesis of M. anisopliae.