Poster: Photosynthesis (light)

Abs # 219: Genes for the regulation of the light-harvesting chlorophyll antenna size in Chlamydomonas reinhardtii

Presenter:	Melis, Anastasios , melis@nature.berkeley.edu
Authors	Melis, Anastasios  ( )   Polle, Juergen  ( )   Kanakagiri, Sarada-devi  ( )
Affiliations:	(A): University Of California, Berkeley

DNA insertional mutagenesis and screening of the green alga Chlamydomonas reinhardtii was employed to isolate tla1, a stable transformant having a truncated light-harvesting chlorophyll antenna size. Molecular analysis showed a single plasmid insertion into an ORF of the nuclear genome corresponding to a novel gene (Tla1) that encodes a protein of 213 amino acids. Genetic analysis showed co-segregation of plasmid and tla1 phenotype. Biochemical analyses showed the tla1 mutant to be chlorophyll deficient, with a functional chlorophyll antenna size of photosystem-II and photosystem-I being about 50% and 65% of the wild type, respectively. It contained a correspondingly lower amount of light-harvesting proteins than the wild type and had lower steady state levels of Lhcb mRNA. The tla1 strain required a higher light intensity for the saturation of photosynthesis and showed greater solar conversion efficiencies and a higher photosynthetic productivity than the wild type under mass culture conditions. Results are discussed in terms of the tla1 mutation, its phenotype, and the role-played by the Tla1 gene in the regulation of the photosynthetic chlorophyll antenna size in Chlamydomonas reinhardtii.