A chloroplast repressible gene expression system in Chlamydomonas reinhardtii: a powerful tool to understand the function of essential plastid genes

Chloroplast biogenesis requires coordination of gene expression between the organellar and nuclear genomes. Sequencing of chloroplast genomes from a large collection of green organisms has revealed the existence of approximately one hundred genes in this organelle present in multiple copies. In the green alga Chlamydomonas reinhardtii, many of these genes have been characterized thanks to its dispensable photo-autotrophic growth in acetate-containing medium and the successful development of plastid transformation methods based on its highly efficient chloroplast homologous recombination system. However, there are still a number of genes for which it has never been possible to disrupt all of their copies. These genes are believed to encode essential factors for growth and survival of the cell. The aim of this thesis was to establish an inducible/repressible expression system for chloroplast genes in Chlamydomonas reinhardtii and to explore its potential for elucidating the role of essential chloroplast genes