Abstract
Every cyanobacterial species possesses multiple genes encoding putative transcriptional regulators (cyAbrBs) having an AbrB-type DNA binding domain at their C-termini. When two genes encoding cyAbrBs in Synechocystis sp. PCC 6803, sll0359 and sll0822, were insertionally disrupted, complete segregation was attained only in the sll0822 mutant. In this study, in order to clarify the physiological roles of multiple cyAbrB copies, we made the overexpression strains of Sll0359 and Sll0822 in either the wild-type or sll0822-disrutped mutant background and analyzed their phenotypes. The phenotypes of sll0822-disrupted mutant such as defects in regulation of nitrogen metabolism and cytokinesis were almost completely suppressed by overexpression of Sll0822 and partially by that of Sll0359, indicating the cooperative function of cyAbrBs. Moreover, the results of co-purification experiment of cyAbrBs suggest the direct interaction of Sll0822 and Sll0359.
