title: Truncated photosystem chlorophyll antenna size in the green microalga Chlamydomonas reinhardtii upon deletion of the TLA3-CpSRP43 gene.
abstract: The truncated light-harvesting antenna size3 (tla3) DNA insertional transformant of Chlamydomonas reinhardtii is a chlorophyll-deficient mutant with a lighter green phenotype, a lower chlorophyll (Chl) per cell content, and higher Chl a/b ratio than corresponding wild-type strains. Functional analyses revealed a higher intensity for the saturation of photosynthesis and greater light-saturated photosynthetic activity in the tla3 mutant than in the wild type and a Chl antenna size of the photosystems that was only about 40% of that in the wild type. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western-blot analyses showed that the tla3 strain was deficient in the Chl a/b light-harvesting complex. Molecular and genetic analyses revealed a single plasmid insertion in chromosome 4 of the tla3 nuclear genome, causing deletion of predicted gene g5047 and plasmid insertion within the fourth intron of downstream-predicted gene g5046. Complementation studies defined that gene g5047 alone was necessary and sufficient to rescue the tla3 mutation. Gene g5047 encodes a C. reinhardtii homolog of the chloroplast-localized SRP43 signal recognition particle, whose occurrence and function in green microalgae has not hitherto been investigated. Biochemical analysis showed that the nucleus-encoded and chloroplast-localized CrCpSRP43 protein specifically operates in the assembly of the peripheral components of the Chl a/b light-harvesting antenna. This work demonstrates that cpsrp43 deletion in green microalgae can be employed to generate tla mutants with a substantially diminished Chl antenna size. The latter exhibit improved solar energy conversion efficiency and photosynthetic productivity under mass culture and bright sunlight conditions.
authors.affiliation: Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.
authors.forename: Henning
authors.initials: H
authors.lastname: Kirst
authors.forename: Jose Gines
authors.initials: JG
authors.lastname: Garcia-Cerdan
authors.forename: Andreas
authors.initials: A
authors.lastname: Zurbriggen
authors.forename: Thilo
authors.initials: T
authors.lastname: Ruehle
authors.forename: Anastasios
authors.initials: A
authors.lastname: Melis
mesh_terms: D015153:Blotting, Western; D019069:Cell Respiration / Q000528:radiation effects; D016825:Chlamydomonas reinhardtii / Q000166:cytology / Q000235:genetics* / Q000378:metabolism* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism*; D060365:Chloroplast Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics; D017353:Gene Deletion; D005816:Genetic Complementation Test; D018745:Genome, Plant / Q000235:genetics; D008027:Light; D058086:Microalgae / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects; D016254:Mutagenesis, Insertional / Q000235:genetics; D010788:Photosynthesis / Q000235:genetics / Q000528:radiation effects; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D010858:Pigmentation / Q000235:genetics / Q000528:radiation effects; D017434:Protein Structure, Tertiary; D020524:Thylakoids / Q000378:metabolism / Q000528:radiation effects
chemical_list: D060365:Chloroplast Proteins; D018744:DNA, Plant; D045322:Photosynthetic Reaction Center Complex Proteins; D002734:Chlorophyll