Abstract
Pheophorbide a oxygenase (PaO) catalyzes oxygenolytic opening of porphyrin macrocycle of pheophorbide a, which is the key step in chlorophyll degradation. We previously reported that PaO was encoded by Accelerated cell death 1 (ACD1) gene. We produced transgenic Arabidopsis plants expressing antisense RNA for ACD1 (As-ACD1) to investigate the cell death processes induced by accumulation of pheophorbide a.
Pheophorbide a was accumulated in As-ACD1 leaves during dark incubation. Dark treated As-ACD1 leaves were bleached upon illumination. It was probably caused by generation of singlet oxygen. We also found that As-ACD1 leaves were not bleached but exhibited cell death when they were incubated in the darkness. This indicate that the accumulation of pheophorbide a induces cell death without generation of singlet oxygen. In order to investigate the light-independent cell death processes, we observed cell ultrastructure and examined the expression of PCD marker genes in As-ACD1 leaves.
