Abstract
Previously, we showed that heat shock strongly enhanced accumulation of transcripts of the htpG and groEL genes in Synechocystis sp. PCC 6803 in the light, but heat induction was much lower in the dark. DCMU and DBMIB differentially affected transcript accumulation of these genes, suggesting that the redox poise of the plastoquinone pool is critical for the HSP gene expression.
In the present study, we examined the effect of light on the heat shock response in detail. Light did not affect stability of the HSP mRNA significantly. The level of the groEL and hsp17 mRNAs did not decrease in the dark for 3 hours after a heat shock. Heat shock strongly enhanced accumulation of the GroEL protein in the light. The acquired thermo-tolerance was greater in the light than in the dark. These results indicate that cyanobacteria have evolved a unique regulatory mechanism by light to induce heat shock genes.
