Abstract
To avoid photoinhibition, an efficient degradation of D1 protein in the repair cycle of photosystem II is required. In higher plants, mounting evidence indicates that FtsH metalloprotease and Deg serine-type proteases play a crucial role in this process. On the other hand, it is well known that D1 is reversibly phosphorylated in a light-dependent manner. The possible role of D1 phosphorylation in PSII repair had been variously suggested, but its significance remains unclear. In this study, we attempt to in vivo assess the role of phosphorylation, mediated by a novel STN8 kinase in D1 degradation. To do this, a double mutant var2 (lacking FtsH2) and stn8 was generated in Arabidopsis. Interestingly, coexistence of var2 and stn8 mitigated the high-light sensitivity of var2 (typical phenotype resulting from photoinhibition). This result suggests contribution of phosphorylation in in vivo D1 degradation in Arabidopsis. Further assessment of the effect of phosphorylation on D1 degradation will be presented.
