International Center for Biotechnology, Osaka University, 2-1 Yamadaoka Suita, Osaka, 565-0871, Japan.
Appl Microbiol Biotechnol. 2012 Mar;93(5):2011-22. doi: 10.1007/s00253-011-3657-9. Epub 2011 Nov 15.
Fungal secondary metabolites have been considered promising resources in the search for novel bioactive compounds. Given the high potential of fungi as genetic resources, it is essential to find an efficient way to link biosynthetic genes to the product in a heterologous system, because many genes for the secondary metabolite in the original strain are silent under standard laboratory conditions. In a previous study, we constructed a heterologous expression system for a biosynthetic gene cluster using Aspergillus oryzae as the host. To make the host more versatile for the expression of secondary metabolism genes, the expression levels of a global regulator, laeA, were increased by placing the A. oryzae laeA gene under the control of the constitutive active pgk promoter. In the A. oryzae overexpressing laeA, two clusters of heterologous biosynthetic genes [the monacolin K (MK) gene cluster from Monascus pilosus and the terrequinone A (TQ) gene cluster from Aspergillus nidulans] were successfully overexpressed, resulting in the production of the corresponding metabolite, MK or TQ. The successful production of secondary metabolites belonging to different structural groups, namely MK as a polyketide and TQ as a hybrid of amino acid and isoprenoid, indicated that the laeA-enriched A. oryzae was a versatile host for the heterologous expression of the biosynthetic gene cluster.
真菌次生代谢产物一直被认为是寻找新型生物活性化合物的有前途的资源。鉴于真菌作为遗传资源的巨大潜力，找到一种有效的方法将生物合成基因与异源系统中的产物联系起来至关重要，因为许多原始菌株中次生代谢产物的基因在标准实验室条件下是沉默的。在之前的一项研究中，我们使用 Aspergillus oryzae 作为宿主构建了一个生物合成基因簇的异源表达系统。为了使宿主更适合表达次生代谢基因，通过将 A. oryzae laeA 基因置于组成型活性 pgk 启动子的控制下，增加了全局调节剂 laeA 的表达水平。在过表达 laeA 的 A. oryzae 中，两个异源生物合成基因簇[来自 Monascus pilosus 的 monacolin K (MK) 基因簇和来自 Aspergillus nidulans 的 terrequinone A (TQ) 基因簇]成功过表达，导致相应代谢产物 MK 或 TQ 的产生。属于不同结构群的次生代谢产物的成功生产，即作为聚酮的 MK 和作为氨基酸和异戊二烯的杂种的 TQ，表明富含 laeA 的 A. oryzae 是生物合成基因簇异源表达的多功能宿主。
