Abstract
Light is indispensable energy for plant, but excessive light induces photoinhibition that results in the light-dependent irreversible inactivation of Photosystem II (PSII). To avoid photoinhibition, an efficient degradation of D1 protein in the repair cycle of photosystem II is important. Mounting evidence indicates that FtsH, an ATP-dependent metalloprotease in thylakoid membranes, and several Deg proteases play key roles in this process. However, it remains unclear how the FtsH-dependent processive degradation of D1 and the Deg-dependent cleavage of lumen-exposed regions of D1 cooperatively act in vivo. In this study, we attempt to elucidate in vivo relationship between major FtsH and Deg isoforms. To do this, an Arabidopsis triple mutant var2 deg5 deg8 was generated; var2 mutant is lacking a major subunit (FtsH2) of FtsH complex, and DEG5 and DEG8 in thylakoid lumen have a synergistic function in the cleavage of the CD loop of D1 protein. The D1 degradation ability and photosynthetic properties in the triple mutant will be presented.
