Abstract
Actinomycetes family including Streptomyces species have been a major source for the discovery of novel natural products (NPs) in the last several decades thanks to their structural novelty, diversity and complexity. Moreover, recent genome mining approach has provided an attractive tool to screen potentially valuable NP biosynthetic gene clusters (BGCs) present in the actinomycetes genomes. Since many of these NP BGCs are silent or cryptic in the original actinomycetes, various techniques have been employed to activate these NP BGCs. Heterologous expression of BGCs has become a useful strategy to produce, reactivate, improve, and modify the pathways of NPs present at minute quantities in the original actinomycetes isolates. However, cloning and efficient overexpression of an entire NP BGC, often as large as over 100 kb, remain challenging due to the ineffectiveness of current genetic systems in manipulating large NP BGCs. This mini review describes examples of actinomycetes NP production through BGC heterologous expression systems as well as recent strategies specialized for the large-sized NP BGCs in Streptomyces heterologous hosts.
Highlights
Natural products (NPs) and their derivatives lead a huge pharmaceutical market share comprising 61% of anticancer drugs and 49% of anti-infection medicine in the past 30 years (Newman and Cragg, 2012)
Since efficient expression of actinomycetes natural products (NPs) biosynthetic gene clusters (BGCs) present a major bottleneck for novel NP discovery, various cryptic BGC awakening strategies such as regulatory genes control, ribosome engineering, co-culture fermentation, and heterologous expression have been pursued for NP development (Tang et al, 2000; Flinspach et al, 2014; Martinez-Burgo et al, 2014; Miyamoto et al, 2014)
Three cloning and heterologous expression systems, which are quite suitable for large NP BGCs, such as transformation-associated recombination (TAR) system, integrase-mediated recombination (IR) system, and plasmid Streptomyces bacterial artificial chromosome system are introduced (Figure 1)
Summary
Natural products (NPs) and their derivatives lead a huge pharmaceutical market share comprising 61% of anticancer drugs and 49% of anti-infection medicine in the past 30 years (Newman and Cragg, 2012). Actinomycetes NPs are a major resource for drug discovery and development, mainly due to their structural novelty, diversity, and complexity (Donadio et al, 2007). Isolation and characterization of NP biosynthetic gene clusters (BGCs) have further accelerated our understanding of their molecular biosynthetic mechanisms, leading to the rational redesign of novel NPs through BGC manipulation (Fischer et al, 2003; Castro et al, 2015). Some of these potentially valuable BGCs are, derived from non-culturable metagenomes or genetically recalcitrant microorganisms. Since efficient expression of actinomycetes NP BGCs present a major bottleneck for novel NP discovery, various cryptic BGC awakening strategies such as regulatory genes control, ribosome engineering, co-culture fermentation, and heterologous expression have been pursued for NP development (Tang et al, 2000; Flinspach et al, 2014; Martinez-Burgo et al, 2014; Miyamoto et al, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
