Poster: Organelle Biogenesis

Abs # 1148: Genes for the regulation of the light-harvesting chlorophyll antenna size in the green alga Chlamydomonas reinhardtii

Presenter:	Komine, Yutaka , ykomine@nature.berkeley.edu
Authors	Komine, Yutaka  (A)   SKanakagiri, Sarada-Devi  (A)   Polle, Juergen  (A) (B)  Melis, Anastasios  (A)
Affiliations:	(A): University of California, Berkeley (B): Brooklyn College

The biotechnology of microalgal mass culture has become a commercially viable industry serving the food, chemical and energy sectors. In a photobiological production process, most important is the solar conversion efficiency and photosynthetic productivity of the culture. Green algae have a tendency to assemble large arrays of Chl antenna molecules, which is a survival strategy under limiting light. Under direct sunlight, however, they absorb in excess of that required for the saturation of photosynthesis and dissipate most of the energy as heat. A smaller, or truncated, Chl antenna size in microalgae could alleviate these optical shortcomings associated with a fully pigmented cell. Objective of this research is to identify genes that confer a truncated Chl antenna size in the model green alga Chlamydomonas reinhardtii. A DNA insertional transformant, having a truncated light-harvesting Chl antenna size was isolated. Molecular and genetic analyses culminated in the cloning of the Tla1 gene (GenBank Accession Nos. AF534570 and AF534571), encoding a cytosol-localized regulatory protein of 213 amino acids. Biochemical analyses showed a tla1 mutant to be Chl deficient, with a smaller Chl antenna size of PSII (50%) and PSI (65%) than the wild type. Results are discussed in terms of the role played by the Tla1 gene in the regulation of the Chl antenna size in Chlamydomonas cells. Two additional putative “truncated Chl antenna size” mutants of Chlamydomonas have been isolated and tentatively referred to as strains A-26 and B-2. These new transformants hold the promise of leading to the identification of additional genes that regulate the Chl antenna size of photosynthesis. Genetic, molecular and biochemical analyses of these mutants will be presented.