Analysis on the factors affecting start-up intensity in the upstream sequence of phycocyanin β subunit gene from Arthrospira platensis by site-directed mutagenesis

Six promoters in the 419 bp upstream sequence of the phycocyanin beta subunit gene of Arthrospira platensis FACHB341 have been previously cloned. Site-directed mutagenesis has now been used to introduce mutations in the -10 and -35 boxes of promoter 3, -10 box of promoter 4, and -35 box of promoter 6. The expression level of green fluorescent protein gene was measured by flow cytometry. Results showed that the effects of site-directed mutagenesis in different promoters were dissimilar: some increased and some declined.