The Stress Response Sll0862Knockout Mutant In Synechocystis Sp. PCC6803

Regulated intramembrane proteolysis (RIP) is a conserved mechanism that regulates signaltransduction across the membrane by recruiting membrane-bound proteases to cleavemembrane-spanning regulatory proteins. The membrane-spanning regulatory proteins can beactivated under stress conditions such as heat shock, salt stress, cold shock and oxidativestress, through RIP and transduce the signal from environment to genomes to regulate geneexpression. Site-2protease (S2P) was first identified in human to involve in the feedbackregulation of sterol and fatty acid synthesis and uptake by controlling the activity oftranscription factors, SREBPs (Sterol regulatory element binding proteins). Bacterial Site-2protease (S2P) play roles in responding to the environmental changes. S2P homologes exist inmammal, bacterial, archaebacteria, eucaryote, high plants and many cyanobacterial.Thecyanobacterial, as the ancestor of chloroplast also have S2P homologes but their functions areelusive. The cyanobacterium Synechocystis sp. PCC6803have four S2P homologes: sll0862,slr0643, sll0528and slr1821. I analyzed the sll0862knockout mutant to explore the functionof sll0862.The results show that there is no difference between mutant and wild type under normalenvironment, so sll0862may have the specific function under stress environments. We usedifferent stress conditions including high temperature, cold shock and oxidative stress todetermine whether the mutants and wild type have different stress response. The results showthat growth rate of wild type and mutants have significant difference under high temperatureand oxidative stress. Meanwhile, chlorophyII fluorescence (values of yield and ETR) understress between wild type and mutant was observed using water-PAM. Significant difference ofchlorophyII fluorescence under oxidative stress was found. No significant difference wasfound between the growth rate of wild type and mutant under salt stress and hyperosmoticstress. The results provide foundations for further research of the sll0862function andmechanism.