to improve the photosynthetic performance of c 3 plants, installing cyanobacterial bicarbonate transporters to the chloroplast inner envelope membrane (IEM) has been proposed for years. In our previous study, we successfully introduced chimeric cyanobacterial sodium-dependent bicarbonate transporters, BicA or SbtA, to the chloroplast IEM of Arabidopsis. However, the installation of authentic BicA and SbtA to the chloroplast IEM has not been achieved yet. In this study, we examined whether or not tobacco etch virus (TEV) protease targeted within chloroplasts can cleave chimeric proteins and produce authentic bicarbonate transporters. To this end, we constructed a TEV protease that carried the transit peptide and expressed it with chimeric BicA or SbtA proteins containing a TEV cleavage site in planta. Chimeric proteins were cleaved only when the TEV protease was co-expressed. The authentic forms of hemagglutinin-tagged BicA and SbtA were detected in the chloroplast IEM. In addition, cleavage of chimeric proteins at the teV recognition site seemed to occur after the targeting of chimeric proteins to the chloroplast IEM. We conclude that the cleavage of chimeric proteins within chloroplasts is an efficient way to install authentic bicarbonate transporters to the chloroplast IEM. Furthermore, a similar approach can be applied to other bacterial plasma membrane proteins.Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the incorporation of CO 2 into ribulose 1,5-bisphosphate (RuBP), which is indispensable for carbohydrate production in plants. However, Rubisco also catalyzes the oxygenation reaction of RuBP. This reaction has been considered wasteful since extra energy is consumed to recover RuBP and CO 2 is partially lost during the process of photorespiration. To compensate for the promiscuous nature of Rubisco, photosynthetic organisms have evolved various CO 2 -concentrating mechanisms (CCMs) 1,2 . For instance, cyanobacterial CCMs possess inorganic carbon (Ci) uptake systems and the microcompartments, carboxysomes, containing Rubisco. To date, five types of active Ci uptake systems have been identified in cyanobacteria. BicA and SbtA are single subunit sodium-dependent bicarbonate transporters on the plasma membrane 3,4 . In contrast, BCT1 is an ATP-binding, cassette-type bicarbonate transporter. The multimeric BCT1 complex is composed of four different subunits 5 . It has been proposed that the installation of CCM to chloroplasts is a promising approach to improve photosynthesis in C 3 plants. According to a theoretical estimation, installing any one of the bicarbonate transporters, BicA, BCT1, or SbtA alone, to the chloroplast inner envelope membrane (IEM) may improve photosynthesis 6-8 .It has been shown that chimeric cyanobacterial bicarbonate transporters expressed in the nucleus can be targeted to the chloroplast IEM 9,10 . Rolland et al. used a membrane protein leader (MPL) sequence that was fused to the N-terminus of the bicarbonate transporter together with the transit peptide 9 , which...