title: Modulation of the light-harvesting chlorophyll antenna size in Chlamydomonas reinhardtii by TLA1 gene over-expression and RNA interference.
abstract: Truncated light-harvesting antenna 1 (TLA1) is a nuclear gene proposed to regulate the chlorophyll (Chl) antenna size in Chlamydomonas reinhardtii. The Chl antenna size of the photosystems and the chloroplast ultrastructure were manipulated upon TLA1 gene over-expression and RNAi downregulation. The TLA1 over-expressing lines possessed a larger chlorophyll antenna size for both photosystems and contained greater levels of Chl b per cell relative to the wild type. Conversely, TLA1 RNAi transformants had a smaller Chl antenna size for both photosystems and lower levels of Chl b per cell. Western blot analyses of the TLA1 over-expressing and RNAi transformants showed that modulation of TLA1 gene expression was paralleled by modulation in the expression of light-harvesting protein, reaction centre D1 and D2, and VIPP1 genes. Transmission electron microscopy showed that modulation of TLA1 gene expression impacts the organization of thylakoid membranes in the chloroplast. Over-expressing lines showed well-defined grana, whereas RNAi transformants possessed loosely held together and more stroma-exposed thylakoids. Cell fractionation suggested localization of the TLA1 protein in the inner chloroplast envelope and potentially in association with nascent thylakoid membranes, indicating a role in Chl antenna assembly and thylakoid membrane biogenesis. The results provide a mechanistic understanding of the Chl antenna size regulation by the TLA1 gene.
authors.affiliation: Department of Plant and Microbial Biology, University of California-Berkeley, CA 94720, USA.
authors.forename: Mautusi
authors.initials: M
authors.lastname: Mitra
authors.forename: Henning
authors.initials: H
authors.lastname: Kirst
authors.forename: David
authors.initials: D
authors.lastname: Dewez
authors.forename: Anastasios
authors.initials: A
authors.lastname: Melis
mesh_terms: D015153:Blotting, Western; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000235:genetics / Q000378:metabolism; D060365:Chloroplast Proteins / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D053141:Organelle Size; D059828:Plant Cells / Q000378:metabolism; D034622:RNA Interference; D020524:Thylakoids / Q000378:metabolism
chemical_list: D060365:Chloroplast Proteins; D045342:Light-Harvesting Protein Complexes; D002734:Chlorophyll; C037184:chlorophyll b