Abstract
Photosynthetic proteins are constantly subjected to photooxidative damage. To minimize the damage, plants had developed PSII repair cycle as a quality-control system, in which the damage was targeted to D1 reaction center protein of PSII. In the PSII repair cycle, photodamaged D1 proteins are specifically degraded by an ATP-dependent metalloprotease FtsH ,which functions as a main factor in this cycle. In Arabidopsis, loss of the major chloroplast FtsHs involved in PSII repair cycle (FtsH2 and FtsH5) results in a typical leaf-variegated phenotype. In contrast to extensive Arabidopsis studies, mutants lacking FtsH are not reported in other species. To further investigate the effect of FtsH deficiency on leaf variegated and PSII repair cycle, we generated FtsH knockdown tobacco plants and characterized their properties. FtsH knockdown tobacco plants showed leaf variegation, although the development and pattern of leaf variegation is distinguishable from that in Arabidopsis variegated mutants such as var2. These transgenic plants also showed decreased PSII photochemical yield Fv/Fm upon high-light irradiation, supporting the important role of FtsH in PSII repair.
