Adaptive evolution provides a high-light stress tolerance in Synechocystis sp. PCC 6803

we obtained a HL tolerant (Tol) strain Synechocystis sp. PCC 6803 by adaptive evolution experiment that the cells were repeatedly subcultured for prolonged periods of time (52 days) under high light stress condition (7000 to 9000 μmol m-2 s-1). Although the growth of the parental strain almost stopped under 9000 μmol m-2 s-1, no growth inhibition was observed in the Tol strain. Furthermore, the growth rate was identical to that of parental strain under low light condition (40 μmol m-2 s-1). To further investigate the high light tolerant mechanisms in the Tol strain, the transcriptome was performed. The transcriptome data suggests the increase of isiA expression in the Tol strain under HL condition. The overexpression of isiA successfully enhanced the HL stress tolerance in the parental strain. The HL tolerant mechanism was different from previous reported mechanisms, such as a reduction of the light-harvesting antenna size. The tolerant strain would be an attractive host for bio-production under high light conditions. Microarray data were obtained from the PCC6803 and Tol grown under 4000 and 7000 μmol m-2 s-1. Three independent experiments were performed under each conditions.