Transformation and expression of Paralichthys olivaceus growth hormone cDNA in Synechocystis sp. PCC6803

The cyanobacterium Synechocystis sp. PCC6803 was transformed with a constructed vector pZGH containing Paralichthys olivaceus (flounder) growth hormone (fGH) cDNA under the control of iron-stressed chlorophyll-binding protein (isiA) promoter. Southern-blotting analysis was employed in verifying the stable integration of introduced DNA. Even after ten successions in medium without kanamycin, the fGH gene could still be detected in the transformed Synechocystis by PCR. The transcription of the foreign gene in induced transformed Synechocystis was tested by RT-PCR. Western-blotting analysis indicated that transformed Synechocystis could express fGH under induction and over 0.2 μg of fGH expression per mg wet transformed Synechocystis was estimated by ELISA–RA. In a bioactivity study, the growth of P. olivaceus was proved to be increased by transformed Synechocystis. At the end of the 49 day feeding trial, the growth rate of P. olivaceus fed with 0.5% transformed Synechocystis was 43% higher than that of the control and the conversion rate of feed declined from 2.0 to 1.6. Whereas Synechocystis at the dose of 2%, increased the growth rate of P. olivaceus by 55% over the control with a feed conversion rate of 1.2. Transformed Synechocystis in fish feed sounds an efficient way of enhancing growth and potentially will have positive impacts on flounder farming industry.