Department of Molecular and Applied Microbiology, Leibniz Institute for Natural Product Research and Infection Biology—Hans Knöll Institute (HKI), Beutenbergstrasse 11a, 07745 Jena, Germany.
Appl Environ Microbiol. 2010 Dec;76(24):8143-9. doi: 10.1128/AEM.00683-10. Epub 2010 Oct 15.
Filamentous fungi produce numerous natural products that constitute a consistent source of potential drug leads, yet it seems that the majority of natural products are overlooked since most biosynthesis gene clusters are silent under standard cultivation conditions. Screening secondary metabolite genes of the model fungus Aspergillus nidulans, we noted a silent gene cluster on chromosome II comprising two nonribosomal peptide synthetase (NRPS) genes, inpA and inpB, flanked by a regulatory gene that we named scpR for secondary metabolism cross-pathway regulator. The induced expression of the scpR gene using the promoter of the alcohol dehydrogenase AlcA led to the transcriptional activation of both the endogenous scpR gene and the NRPS genes. Surprisingly, metabolic profiling of the supernatant of mycelia overexpressing scpR revealed the production of the polyketide asperfuranone. Through transcriptome analysis we found that another silent secondary metabolite gene cluster located on chromosome VIII coding for asperfuranone biosynthesis was specifically induced. Quantitative reverse transcription-PCR proved the transcription not only of the corresponding polyketide synthase (PKS) biosynthesis genes, afoE and afoG, but also of their activator, afoA, under alcAp-scpR-inducing conditions. To exclude the possibility that the product of the inp cluster induced the asperfuranone gene cluster, a strain carrying a deletion of the NRPS gene inpB and, in addition, the alcAp-scpR overexpression cassette was generated. In this strain, under inducing conditions, transcripts of the biosynthesis genes of both the NRPS-containing gene cluster inp and the asperfuranone gene cluster except gene inpB were detected. Moreover, the existence of the polyketide product asperfuranone indicates that the transcription factor ScpR controls the expression of the asperfuranone biosynthesis gene cluster. This expression as well as the biosynthesis of asperfuranone was abolished after the deletion of the asperfuranone activator gene afoA, indicating that ScpR binds to the afoA promoter. To the best of our knowledge, this is the first report of regulatory cross talk between two biosynthesis gene clusters located on different chromosomes.
丝状真菌产生许多天然产物，这些产物构成了潜在药物先导物的持续来源，但似乎大多数天然产物都被忽视了，因为大多数生物合成基因簇在标准培养条件下是沉默的。我们筛选模式真菌构巢曲霉的次级代谢基因时，注意到在染色体 II 上有一个沉默的基因簇，该基因簇包含两个非核糖体肽合酶（NRPS）基因 inpA 和 inpB，由一个我们称为 scpR 的调节基因侧翼，用于次级代谢交叉途径调节。使用醇脱氢酶 AlcA 的启动子诱导 scpR 基因的表达导致内源 scpR 基因和 NRPS 基因的转录激活。令人惊讶的是，过表达 scpR 的菌丝体上清液的代谢谱分析显示产生了多酮化合物 Asperfuranone。通过转录组分析，我们发现另一个位于染色体 VIII 上编码 Asperfuranone 生物合成的沉默次级代谢基因簇被特异性诱导。定量逆转录-PCR 证明，不仅相应的聚酮合酶（PKS）生物合成基因 afoE 和 afoG 的转录，而且它们的激活子 afoA 的转录，在 alcAp-scpR 诱导条件下也被转录。为了排除 inp 簇的产物诱导 Asperfuranone 基因簇的可能性，生成了携带 NRPS 基因 inpB 缺失并且还带有 alcAp-scpR 过表达盒的菌株。在该菌株中，在诱导条件下，检测到包含 NRPS 的基因簇 inp 和 Asperfuranone 基因簇的生物合成基因的转录物，除了基因 inpB。此外，多酮产物 Asperfuranone 的存在表明转录因子 ScpR 控制 Asperfuranone 生物合成基因簇的表达。这种表达以及 Asperfuranone 的生物合成在删除 Asperfuranone 激活子基因 afoA 后被废除，表明 ScpR 结合到 afoA 启动子。据我们所知，这是第一个关于位于不同染色体上的两个生物合成基因簇之间的调控交叉对话的报告。
