Abstract
Most of plastidic proteins are nuclear encoded and are imported into plastids after synthesized in the cytoplasm. Majority of them are synthesized as precursors with plastidic localizing signals, transit peptides, at their amino termini. These proteins are thought to translocate through Toc and Tic complexes in an energy-dependent manner. Toc and Tic complexes are the translocons embedded in both the outer and inner envelope membranes, respectively. Once proteins are imported into plastids, some of them are further targeted to thylakoid membrane. Protein localization systems to thylakoid membrane are different from the Toc-Tic pathway, rather resembled to the bacterial protein secretion systems. There handful of Toc- and Tic-mutants are isolated in Arabidopsis, many of which exhibit pale-green as phenotype. Therefore, protein import through envelope membranes is important for the development of plastids. Current knowledge on protein import into plastids will be discussed at the symposium.
