Abstract
Polyamines play important roles in cell proliferation and stress adaptation. The polyamine content of cells is regulated by biosynthesis, degradation and transport. Synechocystis sp. PCC 6803 can adapt to various environmental stress. However the enzymes involved in polyamine biosynthesis and transport in Synechocystis has not been completely understood. In this study, we found that the growth of Synechocystis was rescued by addition of exogenous polyamine under osmotic stress condition. Synechocystis sp. PCC6803 has several enzymes for polyamine biosynthesis. We isolated the gene encoding homologous arginine decarboxylase. We generated knockdown mutant for the genes, and observed that the mutants required polyamine for their growth. The arginine decarboxylase activities of the gene products were also decreased compared with that of wild type. These results indicate that polyamines are involved in adaptation for osmotic stress and that the genes studied above may participate in the biosynthesis of polyamines.
