Abstract
BackgroundSynechocystis sp. PCC 6803 provides a well-established reference point to cyanobacterial metabolic engineering as part of basic photosynthesis research, as well as in the development of next-generation biotechnological production systems. This study focused on expanding the current knowledge on genomic integration of expression constructs in Synechocystis, targeting a range of novel sites in the chromosome and in the native plasmids, together with established loci used in literature. The key objective was to obtain quantitative information on site-specific expression in reference to replicon copy numbers, which has been speculated but never compared side by side in this host.ResultsAn optimized sYFP2 expression cassette was successfully integrated in two novel sites in Synechocystis chromosome (slr0944; sll0058) and in all four endogenous megaplasmids (pSYSM/slr5037-slr5038; pSYSX/slr6037; pSYSA/slr7023; pSYSG/slr8030) that have not been previously evaluated for the purpose. Fluorescent analysis of the segregated strains revealed that the expression levels between the megaplasmids and chromosomal constructs were very similar, and reinforced the view that highest expression in Synechocystis can be obtained using RSF1010-derived replicative vectors or the native small plasmid pCA2.4 evaluated in comparison. Parallel replicon copy number analysis by RT-qPCR showed that the expression from the alternative loci is largely determined by the gene dosage in Synechocystis, thereby confirming the dependence formerly proposed based on literature.ConclusionsThis study brings together nine different integrative loci in the genome of Synechocystis to demonstrate quantitative differences between target sites in the chromosome, the native plasmids, and a RSF1010-based replicative expression vector. To date, this is the most comprehensive comparison of alternative integrative sites in Synechocystis, and provides the first direct reference between expression efficiency and replicon gene dosage in the context. In the light of existing literature, the findings support the view that the small native plasmids can be notably more difficult to target than the chromosome or the megaplasmids, and that the RSF1010-derived vectors may be surprisingly well maintained under non-selective culture conditions in this cyanobacterial host. Altogether, the work broadens our views on genomic integration and the rational use of different integrative loci versus replicative plasmids, when aiming at expressing heterologous genes in Synechocystis.
Highlights
Microorganisms are routinely engineered by introducing recombinant genetic material into the cell to express individual target proteins, produce specific metabolites, or to study enzyme functions in vivo
Nagy et al Microb Cell Fact (2021) 20:130 more difficult to target than the chromosome or the megaplasmids, and that the RSF1010-derived vectors may be surprisingly well maintained under non-selective culture conditions in this cyanobacterial host
The work broadens our views on genomic integration and the rational use of different integrative loci versus replicative plas‐ mids, when aiming at expressing heterologous genes in Synechocystis
Summary
Microorganisms are routinely engineered by introducing recombinant genetic material into the cell to express individual target proteins, produce specific metabolites, or to study enzyme functions in vivo This can be accomplished by either integrating the expression cassette into the host genome using, for example, homologous recombination, site-specific recombination or transposasemediated gene transposition depending on the organism, or as part of a replicative plasmid [1, 2]. Genomic locus-specific effects that relate to DNA organization and replication with localized effects on transcriptional efficiency (chromosomal position effect) have a significant impact on the expression levels in some microorganisms such as E. coli and S. cerevisiae [5, 8, 9] These factors essentially depend on the organism, and understanding them is important for the rational design of expression systems in basic and applied research. The key objective was to obtain quantitative information on sitespecific expression in reference to replicon copy numbers, which has been speculated but never compared side by side in this host
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.