Abstract
We identified a pale-green mutant, named apg8 (albino or pale-green 8) from screening of RIKEN Arabidopsis Ds tag-lines with knockout genes for nuclear-encoded chloroplast proteins. The gene disrupted by insertion of Ds was found to encode the iron superoxide dismutase, FSD2. FSD from Arabidopsis consists of three members (FSD1, FSD2, FSD3). Phenotype of three alleles of fsd1 showed normal, while two alleles of fsd2 or fsd3 caused pale-green phenotypes, respectively. Moreover, fsd2-1 fsd3-1 showed more severe albino phenotype in the agar plate. The mutant plants were highly sensitive to oxidative stress and had increased levels of reactive oxygen species (ROS) during extended darkness. We also showed that FSD2 and FSD3 proteins form a hetero complex. Taken together, our results provide evidence for essential roles of three FSD members with different functions, and demonstrate that FSD2 and FSD3 act as ROS scavengers in the maintenance of early chloroplast development.
