绿僵菌破坏素合成缺失株中分离鉴定pseurotin A

真菌次级代谢产物是医药活性成分的重要来源之一。就真菌基因组编码的次级代谢基因簇数量而言,由于普遍存在的基因沉默现象,常规培养中能够分离鉴定的化合物种类一般很有限。广谱杀虫的罗伯茨绿僵菌在液体培养基中的主要代谢产物为非核糖体环肽类的破坏素,本研究在对破坏素合成缺失突变株ΔdtxS1进行液体培养时获得了新的产物峰,对其中一个产物峰进行分离、纯化及结构鉴定,确定该化合物为螺环类的pseurotin A。结合在烟曲霉菌中解析的pseurotin A合成途径,推测获得了罗伯茨绿僵菌中的潜在合成基因簇,并推测了pseurotin A在绿僵菌中的合成途径。本研究首次在绿僵菌中鉴定获得pseurotin A,并揭示了在真菌中通过对主要次级代谢产物缺失的方法可以鉴定获得新型的化合物。

Identification of pseurotin A from the destruxin non-producing mutant of Metarhizium robertsii

The secondary metabolites produced by different fungi are the rich sources for pharmaceutical explorations. In terms of the number of the secondary metabolism gene clusters encoded in certain fungal species, only handful of metabolites have been identified due to the effect of gene silencing. In the generalist species of the insect pathogenic fungi such as Metarhizium robertsii, the non-ribosomal cyclopeptide destruxins are the major compounds produced by the fungus grown in artificial liquid media. In this study, we found that the fermentation of the core non-ribosomal peptide synthase gene deletion mutant ΔdtxS1 obtained extra compounds when compared to the wild type (WT) strain of M. robertsii. Purification and structure identification of a chromatographic peak indicated that pseurotin A, a spirocyclic compound, was produced by ΔdtxS1 but not by the WT strain. Based on the elucidation of pseurotin A production in Aspergillus fumigatus, the conserved gene cluster is identified and the putative biosynthetic pathway is proposed in M. robertsii. In conclusion, we first reported the production of pseurotin A by Metarhizium species, and demonstrated that it is an effective way to identify new compounds from fungi by impairment of the production of certain major metabolites.