DNA fragmentation is delayed and persistent in the ptc2-1 mutant. A to D, TUNEL signal at stage 8b (A), stage 9 (B), stage 10 (C), and stage 11 (D) in wild-type (WT). E to H, TUNEL signal at stage 8b (E), stage 9 (F), stage 10 (G), and stage 11 (H) in the ptc2-1 mutant. The red fluorescence shows the propidium iodide staining of anther cells using confocal microscopy; yellow fluorescence shows the TUNEL and PI signal overlap. Msp, microspores; T, tapetum; Tds, tetrads. Scale bars = 20 μm.