Chloroplast Protein Import: Reverse Genetic Approaches

Most proteins required for chloroplast function are encoded in the nuclear genome and have to be translocated into the organelle upon synthesis on cytosolic ribosomes. The translocation is facilitated by a proteinaceous machinery located in the outer and inner chloroplast membrane, the Toc and Tic complexes (translocon at the outer/inner chloroplast membrane). In the past years, many components of these complexes -including receptors, channels and regulatory proteins - have been isolated and characterized biochemically. Recently, the functional analysis of these proteins was complemented by characterization of corresponding loss of function mutants in Arabidopsis thaliana as a model system. Here, we will discuss these in vivo data and the results of expression profiling in the context of current biochemical models.