070-080

organelle biogenesis, posttranscriptional control, RNA binding proteins, RNAi, green alga

Posttranscriptional processes play a major role in chloroplast gene expression. Recent progress in the analysis of the Chlamydomonas reinhardtii genome sequence as well as the use of state-of-the art molecular and biochemical techniques like RNAi approaches and mass spectrometry now enable the identification of novel nucleus-encoded protein factors which regulate the fate of plastidial transcripts and protein synthesis/assembly. Promising candidates are represented by members of the TPR, PPR, and OPR families for many of which a function during chloroplast gene expression could already be assigned. Most, if not all, of these factors are probably organized in higher molecular weight complexes which represent the units mediating regulated gene expression with regard to environmental / developmental signals. Recent work reveals that the spatial organization of this machinery in different plastid subcompartments adds a new level of complexity to chloroplast biogenesis.