Identification of a Gene, Ccr-1 (sll1242), Required for Chill-light Tolerance and Growth at 15 Degrees C in Synechocystis Sp. PCC 6803

Synechocystis sp. PCC 6803 exposed to chill (5 degrees C)-light (100 mumol photons m(-2) s(-1)) stress loses its ability to reinitiate growth. From a random insertion mutant library of Synechocystis sp. PCC 6803, a sll1242 mutant showing increased sensitivity to chill plus light was isolated. Mutant reconstruction and complementation with the wild-type gene confirmed the role of sll1242 in maintaining chill-light tolerance. At 15 degrees C, the autotrophic and mixotrophic growth of the mutant were both inhibited, paralleled by decreased photosynthetic activity. The expression of sll1242 was upregulated in Synechocystis sp. PCC 6803 after transfer from 30 to 15 degrees C at a photosynthetic photon flux density of 30 mumol photons m(-2) s(-1). sll1242, named ccr (cyanobacterial cold resistance gene)-1, may be required for cold acclimation of cyanobacteria in light.