Functional analysis of promoter fragments of salt-tolerance related genes in <I>Spirulina</I>

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In this work, the functions of promoter fragments of two potential salt-tolerance related genes of Spirulina (Spirulina platensis Geitl.) were studied using green fluorescent protein gene (gfp) as a reporter. The promoter structures of two salt-tolerance related genes of Spirulina were predicted using online promoter prediction software. pMD18-T and pUC18 vectors were used to clone the promoter sequences as well as the gfp gene and kanamycine resistance (kan) gene. The fragments containing pro-gfp-kanr were further cloned into pKW1188 vector and the resulting recombinant plasmids were then transformed into a host strain Synechocystis sp. (Synechocystis pevalekii Ercegovic) PCC6803. The resulting bacterial strains were grown under various concentrations of salinity for defining time intervals. The bacterial fluorescence was observed using laser confocal microscope. Our results showed that the transgenic bacteria grown at different concentrations of salinity for various periods produced varying fluorescence intensities. The bacteria treated with NaCl at the concentrations of 0.4mol/L to 0.6mol/L for 6 to 8 h showed the strongest fluorescent intensity. From the result of high salt induced expression of gfp, we predicted that the genes under control of these two promoters are likely to play important roles in the salt tolerance of Spirulina. Accordingly, we believed that a research platform for the studying functions of the promoters of the salt-tolerance related genes in Spirulina has been developed with the gfp as a reporter, the kanr gene as the selection marker, and Synechocystis. sp. PCC6803 as the expression host.