An artificial complementary chromatic acclimation (CCA) system was developed to realize a multiple gene expression system, which was regulated by two colors, red and green lights, using a single photosensor system, the CcaS/CcaR system derived from Synechocystis sp. PCC6803, in Escherichia coli. The development of multiple gene expression systems, especially those based on the physical signals, such as multiple color light irradiations, is challenging. We focused on the remarkable abilities of the cyanobacterial light-regulated gene expression system, CCA, which enables cyanobacteria to change the protein or pigment composition of phycobilisomes and accessory light-harvesting complexes linked to photosystems during exposure to red and green light. In this study, an artificial CCA systems, inspired by type III CCA light-regulated gene expression, was designed by employing a single photosensor system, the CcaS/CcaR green light gene expression system derived from Synechocystis sp. PCC6803, combined with G-box (the regulator recognized by activated CcaR), the cognate cpcG2 promoter, and the constitutively transcribed promoter, the PtrcΔLacO promoter. The E.coli transformants with plasmid-encoded genes, were evaluated at the transcriptional and translational levels under red or green light illumination. Under green light illumination, the transcription and translation of the rfp gene were observed, whereas the expression of the bfp gene was repressed. Under red light illumination, the transcription and translation of the bfp gene, were observed, whereas the expression of the rfp gene was repressed. During the red and green light exposure cycles at every 6 h, BFP expression increased under red light exposure while RFP expression was repressed, and RFP expression increased under green light exposure while BFP expression was repressed.

Artificial complementary chromatic acclimation gene expression system employing cyanobacterial two-component regulation system

ACS Spring 2022

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