Molecular-biological study on the blue light perception system in cyanobacteria

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Blue light specific responses are found throughout the biological kingdoms. However, the molecular mechanism of blue light perception and its signal transduction is not well understood in any organism.The cyanobacterium Synechocystis PCC6803 is a unicellular cyanobacterium which is naturally transformable by exogenously added DNA.Thus, molecular biological techniques can be applied easily to the strain. Thls strain grows under photoautotrophic growth (PAG) condition like other cyanobacteria, but also under photoheterotrophic growth (PHG) condition at the expense of glucose. This strain can also grow under light-activated growth (LAHG) condition in which cultures are incubated in dark and illuminated for 10 min once a day. Blue light is the most effective as daily pulse on the growth under this condition, demonstrating that this cyanobacterium possesses a blue light perception and its signal transduction system.In this study, we have isolated four blue light insensitive mutants of Synechocystis PCC6803. All the mutants are incapable of growing under LAHG condition, but capable of growing under PAG and PHG conditions. These findings suggest that these mutants have mutations in the genes involved in the blue light perception and its signal transduction system. To clone the genes mutants were transformed with the genomic DNA prepared from the wild type. One of the mutants (mutant B) was complemented by the genomic DNA.This finding suggests that the gene involved in the blue light perception and signal transduction system can be cloned from a genomic DNA library by the complementation of the mutant. If the genes could be cloned from this strain, this will lead to study which answers how the organism senses the blue light and transduce the signal.