Modular Cloning Tools for <i>Streptomyces</i> spp. and Application to the De Novo Biosynthesis of Flavokermesic Acid

The filamentous <i>Streptomyces</i> are among the most prolific producers of bioactive natural products and are thus attractive chassis for the heterologous expression of native and designed biosynthetic pathways. Although suitable <i>Streptomyces</i> hosts exist, including genetically engineered cluster-free mutants, the approach is currently limited by the relative paucity of synthetic biology tools facilitating the de novo assembly of multicomponent gene clusters. Here, we report a modular system (MoClo) for <i>Streptomyces</i> including a set of adapted vectors and genetic elements, which allow for the construction of complete genetic circuits. Critical functional validation of each of the elements was obtained using the previously reported β-glucuronidase (GusA) reporter system. Furthermore, we provide proof-of-principle for the toolbox in<i>S. albus</i>, demonstrating the efficient assembly of a biosynthetic pathway to flavokermesic acid (FK), an advanced precursor of the commercially valuable carminic acid.