Cold-induced gene expression and ω(3) fatty acid unsaturation is controlled by red light in Synechocystis.

The expression of cold-induced genes, which are controlled by the cold sensor histidine kinase Hik33, and the formation of ω(3) polyunsaturated fatty acids are controlled by light in the cyanobacterium Synechocystis sp. PCC 6803. Cold-induced Hik33-dependent gene expression is initiated by red light (∼700nm), but not by blue or green light. Red light also turns on the ω(3) fatty acid desaturation. Different combinations of other wavelengths in red spectral region (635 and 726nm) had no effect on the red-light-activated cold-induced transcription or fatty acid desaturation. Therefore, the involvement of phytochrome-like photoreceptor(s), similar to phytochromes of higher plants, in this regulation was not confirmed. The absence of light-dependence of gene expression in the mutant cells deficient in Hik33 suggests the involvement of this histidine kinase in direct or mediated with red light regulation of cold responses in Synechocystis.