title: Enhanced chloroplast transgene expression in a nuclear mutant of Chlamydomonas.
abstract: Chloroplast transformation in microalgae offers great promise for the production of proteins of pharmaceutical interest or for the development of novel biofuels. For many applications, high level expression of transgenes is desirable. We have transformed the chloroplast of Chlamydomonas reinhardtii with two genes, acrV and vapA, which encode antigens from the fish pathogen Aeromonas salmonicida. The promoters and 5' untranslated regions of four chloroplast genes were compared for their ability to drive expression of the bacterial genes. The highest levels of expression were obtained when they were placed under the control of the cis-acting elements from the psaA-exon1 gene. The expression of these chimeric genes was further increased when a nuclear mutation that affects a factor involved in psaA splicing was introduced in the genetic background of the chloroplast transformants. Accumulation of both the chimeric mRNAs and the recombinant proteins was dramatically increased, indicating that negative feedback loops limit the expression of chloroplast transgenes. Our results demonstrate the potential of manipulating anterograde signalling to alter negative regulatory feedback loops in the chloroplast and improve transgene expression.
authors.affiliation: Department of Plant Biology, University of Geneva, Genève, Switzerland.
authors.forename: Laure
authors.initials: L
authors.lastname: Michelet
authors.forename: Linnka
authors.initials: L
authors.lastname: Lefebvre-Legendre
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Burr
authors.forename: Jean-David
authors.initials: JD
authors.lastname: Rochaix
authors.forename: Michel
authors.initials: M
authors.lastname: Goldschmidt-Clermont
mesh_terms: D048409:Aeromonas salmonicida / Q000235:genetics / Q000276:immunology; D000942:Antigens, Bacterial / Q000235:genetics; D002467:Cell Nucleus / Q000235:genetics; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D018506:Gene Expression Regulation, Plant; D005818:Genetic Engineering / Q000379:methods; D009154:Mutation; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics*; D014170:Transformation, Genetic; D019076:Transgenes
chemical_list: D000942:Antigens, Bacterial; D011994:Recombinant Proteins