Rice acyl-CoA-binding proteins OsACBP4 and OsACBP5 are differentially localized in the endoplasmic reticulum of transgenic Arabidopsis

Acyl-CoA-binding proteins (ACBPs) are known to bind and transport acyl-CoA esters and phospholipids intracellularly. In our recent paper in the New Phytologist, we reported that the six acyl-CoA-binding proteins (OsACBPs) in rice (Oryza sativa) are distributed across various subcellular compartments in transgenic Arabidopsis (Arabidopsis thaliana) such as the cytosol (OsACBP1, OsACBP2 and OsACBP3), the endoplasmic reticulum (ER) including the tubules (OsACBP4 and OsACBP5) and the cisternae (OsACBP4), and the peroxisomes (OsACBP6). Localization of OsACBP4::GFP to the peripheral ER cisternae and the central cisternal ER-like structures in transgenic Arabidopsis distinguished it from OsACBP5::GFP. We further report that besides the ER, OsACBP4::GFP and OsACBP5::GFP were both targeted to the membranes of ER bodies and ER-derived spherical structures in transgenic Arabidopsis. These findings support our previous conclusion that OsACBP4 and OsACBP5 are not redundant proteins in the ER.