Fig. 2.

Growth-dependent cell death phenotype of the Atoep16-1 mutant. (A–F) Atoep16-1 (A–C) and wild-type (D–F) plants were grown in the dark (A and D) under a nonpermissive dark-to-light shift (B and E) or under permissive continuous white light (C and F) and inspected under a microscope. Accumulation of free, red-fluorescing Pchlide was monitored under blue light (400–500 nm) (A and D). Free, excited Pchlide molecules present in etiolated Atoep16-1 (A) but not in wild-type (D) plants caused photooxidative damages, as a result of which the seedlings died (B versus E, respectively). (G) Seedling survival rates of wild-type (open circles), Atoep16-1 (triangles), and flu (filled circles) plants during a nonpermissive dark-to-light shift. Of a number of 300 seedlings in three independent experiments, the indicated percentages survived, whereas the remainder died as a result of pigment-sensitized photooxidation. (H) Pigment accumulation in etiolated wild-type (gray line), Atoep16-1 (blue line), and flu (red line) plants. The different peaks were identified as Pchlide b (peak eluting at 12.5 min) and Pchlide a (peak eluting at 15 min) by using synthetic standards and absorbance measurements as well as mass spectrometry (SI Fig. 8).