• Molecules and Cells
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• 제43권6호
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• pp.509-516
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• 2020

To perceive fluctuations in light quality, quantity, and timing, higher plants have evolved diverse photoreceptors including UVR8 (a UV-B photoreceptor), cryptochromes, phototropins, and phytochromes (Phys). In contrast to plants, prokaryotic oxygen-evolving photosynthetic organisms, cyanobacteria, rely mostly on bilin-based photoreceptors, namely, cyanobacterial phytochromes (Cphs) and cyanobacteriochromes (CBCRs), which exhibit structural and functional differences compared with plant Phys. CBCRs comprise varying numbers of light sensing domains with diverse color-tuning mechanisms and signal transmission pathways, allowing cyanobacteria to respond to UV-A, visible, and far-red lights. Recent genomic surveys of filamentous cyanobacteria revealed novel CBCRs with broader chromophore-binding specificity and photocycle protochromicity. Furthermore, a novel Cph lineage has been identified that absorbs blue-violet/yellow-orange light. In this minireview, we briefly discuss the diversity in color sensing and signal transmission mechanisms of Cphs and CBCRs, along with their potential utility in the field of optogenetics.

• 한국미생물학회:학술대회논문집
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• 한국미생물학회 2005년도 International Meeting of the Microbiological Society of Korea
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• pp.64-66
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• 2005

Photosynthetic microbes possess a wealth of photoactive proteins including chlorophyll-based pigments, phototropin-related blue light receptors, phytochromes, and cryptochromes. Surprisingly, recent genome sequencing projects discovered additional photoactive proteins, retinal-based rhodopsins, in cyanobacterial and algal genera. Most of these newly found rhodopsin genes and retinal synthase have not been expressed and their functions are unknown. Analysis of the Anabaena and Chlamyrhodopsin with retinal synthase revealed that they have sensory functions, which, based on our work with haloarchaeal rhodopsins, may use a variety of signaling mechanisms. Anabaena rhodopsin is believed to be sensory, shown to interact with a soluble transducer and the putative function is either chromatic adaptation or circadian rhythm. Chlamydomonas rhodopsins are involved in phototaxis and photophobic responses based on electrical measurements by RNAi experiment. In order to analyze the protein, we developed a sensory rhodopsin expression system in E. coli. The opsin in E. coil bound endogenous all-trans retinal to form a pigment and can be observed on the plate. Using this system we could identify retinal synthase in Anabaena PCC 7120. We conclude that Anabaena D475 dioxygenase functions as a retinal synthase to the Anabaena rhodopsin in the cell.

• Plant Biotechnology Reports
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• 제4권2호
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• pp.149-155
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• 2010

Expression of the genes for carotenoid bio-synthesis (crt) is dependent on light, but little is known about the underlying mechanism of light sensing and signalling in the cyanobacterium Synechocystis sp. PCC 6803 (hereafter, Synechocystis). In the present study, we investigated the light-induced increase in the transcript levels of Synechocystis crt genes, including phytoene synthase (crtB), phytoene desaturase (crtP), ${\zeta}$-carotene desaturase (crtQ), and ${\beta}$-carotene hydroxylase (crtR), during a darkto-light transition period. During the dark-to-light shift, the increase in the crt transcript levels was not affected by mutations in cyanobacterial photoreceptors, such as phytochromes (cph1, cph2 and cph3) and a cryptochrome-type photoreceptor (ccry), or respiratory electron transport components NDH and Cyd/CtaI. However, treatment with photosynthetic electron transport inhibitors significantly diminished the accumulation of crt gene transcripts. Therefore, the light induction of the Synechocystis crt gene expression is most likely mediated by photosynthetic electron transport rather than by cyanobacterial photoreceptors during the dark-to-light transition.