Abstract
BackgroundExotic genes, especially clustered multiple-genes for a complex pathway, are normally integrated into chromosome for heterologous expression. The influences of insertion sites on heterologous expression and allotropic expressions of exotic genes on host remain mostly unclear.ResultsWe compared the integration and expression efficiencies of single and multiple exotic genes that were inserted into Myxococcus xanthus genome by transposition and attB-site-directed recombination. While the site-directed integration had a rather stable chloramphenicol acetyl transferase (CAT) activity, the transposition produced varied CAT enzyme activities. We attempted to integrate the 56-kb gene cluster for the biosynthesis of antitumor polyketides epothilones into M. xanthus genome by site-direction but failed, which was determined to be due to the insertion size limitation at the attB site. The transposition technique produced many recombinants with varied production capabilities of epothilones, which, however, were not paralleled to the transcriptional characteristics of the local sites where the genes were integrated. Comparative transcriptomics analysis demonstrated that the allopatric integrations caused selective changes of host transcriptomes, leading to varied expressions of epothilone genes in different mutants.ConclusionsWith the increase of insertion fragment size, transposition is a more practicable integration method for the expression of exotic genes. Allopatric integrations selectively change host transcriptomes, which lead to varied expression efficiencies of exotic genes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-015-0294-5) contains supplementary material, which is available to authorized users.
Highlights
Exotic genes, especially clustered multiple-genes for a complex pathway, are normally integrated into chromosome for heterologous expression
Our results indicated that allopatric integrations selectively change host transcriptomes, leading to varied expression efficiencies of exotic genes in M. xanthus
To test whether insertion pattern influences heterologous expression, we introduced the chloramphenicol acetyl transferase gene into the genome of M. xanthus DZ2 via either transposition (Tp) or site-directed insertion (Mx8)
Summary
Especially clustered multiple-genes for a complex pathway, are normally integrated into chromosome for heterologous expression. Multiple genes of complicated biosynthetic pathways are often integrated into chromosome for heterologous expression. The productions of epothilones are greatly varied in those engineered Myxococcus strains, even with almost identical genetic backgrounds [10, 11], suggesting internal uncertainty for the expression of multiple exotic genes. It is yet unclear whether and how insertion sites influence the expression efficiency of exotic genes and whether and how allotropic expressions influence on host cells
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