Direct cloning and reassembly of secondary metabolite biosynthetic gene clusters. (A) To capture a long cluster, a linear cloning vector flanked with homology arms is
prepared and then co-transferred with the cluster-harboring genomic DNA into yeast (TAR) or engineered Escherichia coli (LLHR). Catalyzed by the native recombination
mechanism in yeast or expressed Red/ET in E. coli, the homologous recombination between the cluster ends and the vector homology arms yields a circular replicable
construct. (B) For reassembly of a cluster, genes are isolated individually by PCR, subcloning, or chemical synthesis, and are modified by the addition of homology ends, ends
with restriction sites, or specific recombination sites. Strong or inducible promoters can be introduced in front of genes. Next, the gene fragments are assembled in a vector by in
vivo homologous recombination in yeast, or by in vitro site-specific recombination or ligation. Assembled products can be further amplified in E. coli.