No coordinated transcriptional regulation of the sod-kat antioxidative system in Synechocystis sp PCC 6803

The balanced expression of antioxidative enzymes is believed to be important for effective protection against oxidative stress. The cyanobacterium Synechocystis sp, PCC6803 possesses the simplest antioxidative system, i.e., a single sod gene (sodB) for SOD and a single kat gene (katG) for catalase/peroxidase, so that it is an ideal model for analyzing the balance of expression. Here we show that sodB expression is induced by various stresses, i.e., O-2(-), H2O2, low and high temperatures and high salinity, whereas katG is constitutively expressed. These results suggest that coordinated expression is not essential for antioxidative protection at least in this cyanobacteria. The implications of these phenomena are discussed.