PARENT SESSION
Posters P6B Photosynthetic acclimation: Mechanisms and gene expression. Abstracts (531-578)

Characterization of the cyanobacterial mutants that cannot grow under high-light condition. Tamaki Fujimori^*,1, Hanayo Sato¹, Kintake Sonoike¹, ¹ Department of Integrated Biosciences, Kashiwa City, Chiba Prefecture, Japan

ABSTRACT- In response to high light, photosynthetic organisms change their photosynthetic apparatus in order to avoid the photodamage. In cyanobacteria, high-light acclimation includes reduction of antenna size, activation of PSII reaction center protein turnover, enhancement of scavenging system for reactive oxygen species, up-regulation of CO₂ fixation, state transition and regulation of photosystem stoichiometry. In this study, we aimed to isolate mutants, which have the defect in high-light acclimation, by the screening under high light condition. The psaK2 mutant, which could not perform state transition, was not able to grow on the plate under high-light condition. The growth of the sll1961 mutant, which failed to modulate photosystem stoichiometry, was also inhibited in liquid culture under prolonged high-light condition. These results imply that the defect in high-light acclimation prominently affect the growth under high-light condition. We created mutants by transposon-mediated random insertion of chloramphenicol-resistant cassette into the chromosome of the wild type and screened mutants which could not grow on the plate under high-light condition. We have identified four mutants that could not grow under high-light condition so far. The characterization of these mutants revealed that some of the mutants actually have defects in high light acclimation such as state transition.

KEY WORDS: high light, cyanobacteria, screening, state transition