Figure 3.

The DNA relaxation activity of TOP1α is crucial for the genome integrity and survival of SSCs. A and B, TUNEL assay of DNA fragmentation (stained in green) in root tip cells of wild-type and top1α seedlings. C and D, Root tips of wild-type seedlings treated with 100 nm CPT for 6 h (C) and 24 h (D). E and F, Root tips of top1α seedlings carrying the TOP1αN871S transgene, which were mock-treated for 24 h (E) or treated with 100 nm CPT for 24 h (F). G, Root tip of a top1α seedling treated with 48 μm APH for 24 h. H, Root tip of wild-type seedlings treated with 48 µm APH (inset) or 48 µm APH and 100 nm CPT for 24 h. Cells were counterstained with PI and imaged with confocal microscopy. Arrowheads point to the QC. M, Mock. Bars = 25 μm.