Kessler Felix, Schnell Danny J
Laboratoire de Physiologie Végétale, Institut de Botanique, Université de Neuchâtel, Rue Emile-Argand 11, 2007 Neuchâtel, Switzerland.
Traffic. 2006 Mar;7(3):248-57. doi: 10.1111/j.1600-0854.2005.00382.x.
The photosynthetic chloroplast is the hallmark organelle of green plants. During the endosymbiotic evolution of chloroplasts, the vast majority of genes from the original cyanobacterial endosymbiont were transferred to the host cell nucleus. Chloroplast biogenesis therefore requires the import of nucleus-encoded proteins from their site of synthesis in the cytosol. The majority of proteins are imported by the activity of Toc and Tic complexes located within the chloroplast envelope. In addition to chloroplasts, plants have evolved additional, non-photosynthetic plastid types that are essential components of all cells. Recent studies indicate that the biogenesis of various plastid types relies on distinct but homologous Toc-Tic import pathways that have specialized in the import of specific classes of substrates. These different import pathways appear to be necessary to balance the essential physiological role of plastids in cellular metabolism with the demands of cellular differentiation and plant development.
光合叶绿体是绿色植物的标志性细胞器。在叶绿体的内共生进化过程中，绝大多数来自原始蓝细菌内共生体的基因被转移到宿主细胞核中。因此，叶绿体生物发生需要从其在细胞质中的合成位点导入细胞核编码的蛋白质。大多数蛋白质是通过位于叶绿体包膜内的Toc和Tic复合物的活性导入的。除了叶绿体，植物还进化出了其他非光合质体类型，它们是所有细胞的重要组成部分。最近的研究表明，各种质体类型的生物发生依赖于不同但同源的Toc-Tic导入途径，这些途径专门用于导入特定类别的底物。这些不同的导入途径似乎对于平衡质体在细胞代谢中的基本生理作用与细胞分化和植物发育的需求是必要的。
