title: Repression of essential chloroplast genes reveals new signaling pathways and regulatory feedback loops in chlamydomonas.
abstract: Although reverse genetics has been used to elucidate the function of numerous chloroplast proteins, the characterization of essential plastid genes and their role in chloroplast biogenesis and cell survival has not yet been achieved. Therefore, we developed a robust repressible chloroplast gene expression system in the unicellular alga Chlamydomonas reinhardtii based mainly on a vitamin-repressible riboswitch, and we used this system to study the role of two essential chloroplast genes: ribosomal protein S12 (rps12), encoding a plastid ribosomal protein, and rpoA, encoding the α-subunit of chloroplast bacterial-like RNA polymerase. Repression of either of these two genes leads to the arrest of cell growth, and it induces a response that involves changes in expression of nuclear genes implicated in chloroplast biogenesis, protein turnover, and stress. This response also leads to the overaccumulation of several plastid transcripts and reveals the existence of multiple negative regulatory feedback loops in the chloroplast gene circuitry.
authors.affiliation: Department of Molecular Biology and Plant Biology, University of Geneva, 1211 Geneva, Switzerland.
authors.forename: Silvia
authors.initials: S
authors.lastname: Ramundo
authors.forename: Michèle
authors.initials: M
authors.lastname: Rahire
authors.forename: Olivier
authors.initials: O
authors.lastname: Schaad
authors.forename: Jean-David
authors.initials: JD
authors.lastname: Rochaix
mesh_terms: D020418:Algal Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D060365:Chloroplast Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D016000:Cluster Analysis; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D025461:Feedback, Physiological; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D020043:Genes, Essential; D007106:Immune Sera; D008969:Molecular Sequence Data; D011132:Polyribosomes; D014176:Protein Biosynthesis; D011817:Rabbits; D012269:Ribosomal Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017422:Sequence Analysis, DNA; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D020418:Algal Proteins; D060365:Chloroplast Proteins; D007106:Immune Sera; D012269:Ribosomal Proteins; C034212:ribosomal protein S12; D012321:DNA-Directed RNA Polymerases