title: Specific and Efficient Targeting of Cyanobacterial Bicarbonate Transporters to the Inner Envelope Membrane of Chloroplasts in Arabidopsis.
abstract: Installation of cyanobacterial bicarbonate transporters to the inner envelope membrane (IEM) of chloroplasts in C3 plants has been thought to improve photosynthetic performance. However, the method to deliver cyanobacterial bicarbonate transporters to the chloroplast IEM remains to be established. In this study, we provide evidence that the cyanobacterial bicarbonate transporters, BicA and SbtA, can be specifically installed into the chloroplast IEM using the chloroplast IEM targeting signal in conjunction with the transit peptide. We fused the transit peptide and the mature portion of Cor413im1, whose targeting mechanism to the IEM has been characterized in detail, to either BicA or SbtA isolated from Synechocystis sp. PCC6803. Among the seven chimeric constructs tested, we confirmed that four chimeric bicarbonate transporters, designated as BicAI, BicAII, SbtAII, and SbtAIII, were expressed in Arabidopsis. Furthermore, these chimeric transporters were specifically targeted to the chloroplast IEM. They were also resistant to alkaline extraction but can be solubilized by Triton X-100, indicating that they are integral membrane proteins in the chloroplast IEM. One of the transporters, BicA, could reside in the chloroplast IEM even after removal of the IEM targeting signal. Taken together, our results indicate that the addition of IEM targeting signal, as well as the transit peptide, to bicarbonate transporters allows us to efficiently target nuclear-encoded chimeric bicarbonate transporters to the chloroplast IEM.
authors: Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki Miyazaki, Japan.
authors: Susumu
authors: S
authors: Uehara
authors: Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki Miyazaki, Japan.
authors: Fumi
authors: F
authors: Adachi
authors: Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of MiyazakiMiyazaki, Japan; Organization for Promotion of Tenure Track, University of MiyazakiMiyazaki, Japan.
authors: Yasuko
authors: Y
authors: Ito-Inaba
authors: Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki Miyazaki, Japan.
authors: Takehito
authors: T
authors: Inaba
keywords: Arabidopsis; bicarbonate transporter; chloroplast; cyanobacteria; protein targeting