Optimization of exogenous gene expression in Synechococcus sp. PCC 7002

Due to its photoautrophic growth in ocean water the cyanobacterium Synechococcus sp. PCC 7002 is an attractive organism for the sustainable production of chemicals and fuels.  However, gene expression tools commonly used in other microorganisms are unavailable for Synechococcus sp. PCC 7002.  Our group previously identified a series of LacI-regulated promoters allowing expression of yellow fluorescent protein (YFP) over a wide dynamic range in Synechococcus sp. PCC 7002.  However, substituting YFP for an exogenous gene resulted in poor expression of that gene.  Bioinformatic analysis revealed sub-optimal translation initiation rates presumably due to sequestration of the ribosome binding site by the nucleotides within the open reading frame of the exogenous gene.  To circumvent this problem a series of expression constructs were created including bioinformatically informed ribosome binding sites unhindered by the nucleotide sequence of the exogenous gene and translationally coupled operons.  Exogenous gene expression was qualified by determining the whole cell abundance of the protein product by western blotting.  These data strengthen our understanding of exogenous gene expression in Synechococcus sp. PCC 7002.