J. Gen. Appl. Microbiol

None of the authors of this manuscript has any financial or personal relationship with other people or organizations that could inappropriately influence their work. acteristic that has facilitated their use as a model organism for photosynthesis, nitrogen fixation (Herrero and Flores, 2008), environmental stress tolerance (Los et al., 2010; Muramatsu and Hihara, 2012), and the evolution of plastid endosymbiosis (McFadden, 2014). Recently, cyanobacteria have been studied for the production of biofuels and biomaterials because they can directly convert carbon dioxide to biomass and beneficial metabolites by photosynthesis and they grow faster than plants (Angermayr et al., 2015). Therefore, production systems using cyanobacteria from renewable resources are expected to contribute not only to sustainable energy generation but also to mitigate the effects of global warming by the uptake of atmospheric CO2. Among cyanobacteria, Synechocystis sp. PCC 6803 (hereafter called Synechocystis) is the most studied strain, and a large amount of genomic and physiological information about this organism has been generated over the years. Synechocystis was the first photosynthetic organism to have its genome sequenced (Kaneko et al., 1996), which comprises a 3.6-Mb chromosome and seven plasmids. Moreover, it is naturally transformable, and a number of molecular tools are available for its genetic manipulation (Heidorn et al., 2011; Koksharova and Wolk, 2002). Several expression systems that regulate transcription levels have been developed in Synechocystis (Berla et al., 2013): metabolite-inducible promoters, such as the LacI repressor-lacO operator system induced by the addition of isopropyl b-D-1-thiogalactopyranoside (IPTG) (Guerrero et al., 2012; Huang et al., 2010); metal-inducible promoters (Guerrero et al., 2012; Kunert et al., 2003; Peca et al., 2007; Schuergers et al., 2014); and light-inducible promoters, induced by high-intensity light (Berto et al., 2011; Lindberg et al., 2010) or green light (Abe et al., 2014). The trc promoter, a part of the IPTG-inducible A tightly inducible riboswitch system in Synechocystis sp. PCC 6803