Sucrose accumulation in salt-stressed cells ofagpgene deletion-mutant in cyanobacteriumSynechocystissp. PCC 6803

The agp gene encoding the ADP-glucose pyrophosphorylase is involved in cyanobacterial glycogen synthesis and glucosylglycerol formation. By in vitro DNA recombination technology, a mutant with partial deletion of agp gene in the cyanobacterium Synechocystis sp. PCC 6803 was constructed. This mutant could not synthesize glycogen or the osmoprotective substance glucosylglycerol. In the mutant cells grown in the medium containing 0.9 M NaCl for 96 h, no glucosylglycerol was detected and the total amount of sucrose was 29 times of that of in wild-type cells. Furthermore, the agp deletion mutant could tolerate up to 0.9 M salt concentration. Our results suggest that sucrose might act as a similar potent osmoprotectant as glucosylglycerol in cyanobacterium Synechocystis sp. PCC 6803.