Identification and Biotechnological Application of Novel Regulatory Genes Involved inStreptomycesPolyketide Overproduction through Reverse Engineering Strategy

Abstract

Polyketide belongs to a family of abundant natural products typically produced by the filamentous soil bacteria Streptomyces. Similar to the biosynthesis of most secondary metabolites produced in the Streptomyces species, polyketide compounds are synthesized through tight regulatory networks in the cell, and thus extremely low levels of polyketides are typically observed in wild-type strains. Although many Streptomyces polyketides and their derivatives have potential to be used as clinically important pharmaceutical drugs, traditional strain improvement strategies such as random recursive mutagenesis have long been practiced with little understanding of the molecular basis underlying enhanced polyketide production. Recently, identifying, understanding, and applying a novel polyketide regulatory system identified from various Omics approaches, has become an important tool for rational Streptomyces strain improvement. In this paper, DNA microarray-driven reverse engineering efforts for improving titers of polyketides are briefly summarized, primarily focusing on our recent results of identification and application of novel global regulatory genes such as wblA, SCO1712, and SCO5426 in Streptomyces species. Sequential targeted gene manipulation involved in polyketide biosynthetic reguation synergistically provided an efficient and rational strategy for Streptomyces strain improvement. Moreover, the engineered regulation-optimized Streptomyces mutant strain was further used as a surrogate host for heterologous expression of polyketide pathway.

The re-emergence of natural products for drug discovery in the genomics era

“…However, owing to the intrinsic molecular complexity of polyketides, chemical synthesis is not commercially viable. Gene clusters are involved in every step of the production of biologically active polyketides 160 , and manipulating the biosynthetic gene clusters can allow more economical and efficient production of chirally pure polyketide compounds 161 . Two examples, epitholone 162 and lomaiviticin 163 , are presented in Figure 3.…”

Regulation of antibiotic biosynthesis in actinomycetes: Perspectives and challenges

“…Other examples include deletion of genes encoding GntR family regulators for nucleoside antibiotic A201A overproduction in Marinactinospora thermotolerans 00652, and platensimycin and platencin overproduction in Streptomyces platensis [ 90 , 91 ], GBL receptors for validamycin overproduction in S. hygroscopicus 5008 [ 92 ], SgcR for lidamycin overproduction (C-1027) in S. globisporus [ 93 ], and PhaR for daptomycin overproduction in S. roseosporus [ 94 ]. It is not uncommon that deletion of multiple repressors are required to further increase antibiotic titers [ 95 ]. To achieve maximal level of antibiotic production, it requires a systematic manipulation of deletion of repressors in combination with overexpression of activators [ 93 , 96 , 97 ].…”

Rational engineering of Streptomyces albus J1074 for the overexpression of secondary metabolite gene clusters

“…S. albus has a recorded ability to heterologously express other type II polyketides [ 55 ]. Nae et al [ 56 ] have constructed a S. coelicolor Δ pfk Δ wblA ΔSCO1712 triple mutant that also showed a synergistic effect in stimulating actinorhodin and other type II polyketide biosynthesis [ 57 ]. We attempted to delete SCO1712 homologue gene in S. albus but our efforts were unsuccessful using both recombineering (REDIRECT method) and CRISPR/Cas9 approaches.…”